| File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Analysis/ScalarEvolution.cpp |
| Warning: | line 3923, column 7 Called C++ object pointer is null |
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| 1 | //===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===// | |||
| 2 | // | |||
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | |||
| 4 | // See https://llvm.org/LICENSE.txt for license information. | |||
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |||
| 6 | // | |||
| 7 | //===----------------------------------------------------------------------===// | |||
| 8 | // | |||
| 9 | // This file contains the implementation of the scalar evolution analysis | |||
| 10 | // engine, which is used primarily to analyze expressions involving induction | |||
| 11 | // variables in loops. | |||
| 12 | // | |||
| 13 | // There are several aspects to this library. First is the representation of | |||
| 14 | // scalar expressions, which are represented as subclasses of the SCEV class. | |||
| 15 | // These classes are used to represent certain types of subexpressions that we | |||
| 16 | // can handle. We only create one SCEV of a particular shape, so | |||
| 17 | // pointer-comparisons for equality are legal. | |||
| 18 | // | |||
| 19 | // One important aspect of the SCEV objects is that they are never cyclic, even | |||
| 20 | // if there is a cycle in the dataflow for an expression (ie, a PHI node). If | |||
| 21 | // the PHI node is one of the idioms that we can represent (e.g., a polynomial | |||
| 22 | // recurrence) then we represent it directly as a recurrence node, otherwise we | |||
| 23 | // represent it as a SCEVUnknown node. | |||
| 24 | // | |||
| 25 | // In addition to being able to represent expressions of various types, we also | |||
| 26 | // have folders that are used to build the *canonical* representation for a | |||
| 27 | // particular expression. These folders are capable of using a variety of | |||
| 28 | // rewrite rules to simplify the expressions. | |||
| 29 | // | |||
| 30 | // Once the folders are defined, we can implement the more interesting | |||
| 31 | // higher-level code, such as the code that recognizes PHI nodes of various | |||
| 32 | // types, computes the execution count of a loop, etc. | |||
| 33 | // | |||
| 34 | // TODO: We should use these routines and value representations to implement | |||
| 35 | // dependence analysis! | |||
| 36 | // | |||
| 37 | //===----------------------------------------------------------------------===// | |||
| 38 | // | |||
| 39 | // There are several good references for the techniques used in this analysis. | |||
| 40 | // | |||
| 41 | // Chains of recurrences -- a method to expedite the evaluation | |||
| 42 | // of closed-form functions | |||
| 43 | // Olaf Bachmann, Paul S. Wang, Eugene V. Zima | |||
| 44 | // | |||
| 45 | // On computational properties of chains of recurrences | |||
| 46 | // Eugene V. Zima | |||
| 47 | // | |||
| 48 | // Symbolic Evaluation of Chains of Recurrences for Loop Optimization | |||
| 49 | // Robert A. van Engelen | |||
| 50 | // | |||
| 51 | // Efficient Symbolic Analysis for Optimizing Compilers | |||
| 52 | // Robert A. van Engelen | |||
| 53 | // | |||
| 54 | // Using the chains of recurrences algebra for data dependence testing and | |||
| 55 | // induction variable substitution | |||
| 56 | // MS Thesis, Johnie Birch | |||
| 57 | // | |||
| 58 | //===----------------------------------------------------------------------===// | |||
| 59 | ||||
| 60 | #include "llvm/Analysis/ScalarEvolution.h" | |||
| 61 | #include "llvm/ADT/APInt.h" | |||
| 62 | #include "llvm/ADT/ArrayRef.h" | |||
| 63 | #include "llvm/ADT/DenseMap.h" | |||
| 64 | #include "llvm/ADT/DepthFirstIterator.h" | |||
| 65 | #include "llvm/ADT/EquivalenceClasses.h" | |||
| 66 | #include "llvm/ADT/FoldingSet.h" | |||
| 67 | #include "llvm/ADT/None.h" | |||
| 68 | #include "llvm/ADT/Optional.h" | |||
| 69 | #include "llvm/ADT/STLExtras.h" | |||
| 70 | #include "llvm/ADT/ScopeExit.h" | |||
| 71 | #include "llvm/ADT/Sequence.h" | |||
| 72 | #include "llvm/ADT/SetVector.h" | |||
| 73 | #include "llvm/ADT/SmallPtrSet.h" | |||
| 74 | #include "llvm/ADT/SmallSet.h" | |||
| 75 | #include "llvm/ADT/SmallVector.h" | |||
| 76 | #include "llvm/ADT/Statistic.h" | |||
| 77 | #include "llvm/ADT/StringRef.h" | |||
| 78 | #include "llvm/Analysis/AssumptionCache.h" | |||
| 79 | #include "llvm/Analysis/ConstantFolding.h" | |||
| 80 | #include "llvm/Analysis/InstructionSimplify.h" | |||
| 81 | #include "llvm/Analysis/LoopInfo.h" | |||
| 82 | #include "llvm/Analysis/ScalarEvolutionDivision.h" | |||
| 83 | #include "llvm/Analysis/ScalarEvolutionExpressions.h" | |||
| 84 | #include "llvm/Analysis/TargetLibraryInfo.h" | |||
| 85 | #include "llvm/Analysis/ValueTracking.h" | |||
| 86 | #include "llvm/Config/llvm-config.h" | |||
| 87 | #include "llvm/IR/Argument.h" | |||
| 88 | #include "llvm/IR/BasicBlock.h" | |||
| 89 | #include "llvm/IR/CFG.h" | |||
| 90 | #include "llvm/IR/Constant.h" | |||
| 91 | #include "llvm/IR/ConstantRange.h" | |||
| 92 | #include "llvm/IR/Constants.h" | |||
| 93 | #include "llvm/IR/DataLayout.h" | |||
| 94 | #include "llvm/IR/DerivedTypes.h" | |||
| 95 | #include "llvm/IR/Dominators.h" | |||
| 96 | #include "llvm/IR/Function.h" | |||
| 97 | #include "llvm/IR/GlobalAlias.h" | |||
| 98 | #include "llvm/IR/GlobalValue.h" | |||
| 99 | #include "llvm/IR/GlobalVariable.h" | |||
| 100 | #include "llvm/IR/InstIterator.h" | |||
| 101 | #include "llvm/IR/InstrTypes.h" | |||
| 102 | #include "llvm/IR/Instruction.h" | |||
| 103 | #include "llvm/IR/Instructions.h" | |||
| 104 | #include "llvm/IR/IntrinsicInst.h" | |||
| 105 | #include "llvm/IR/Intrinsics.h" | |||
| 106 | #include "llvm/IR/LLVMContext.h" | |||
| 107 | #include "llvm/IR/Metadata.h" | |||
| 108 | #include "llvm/IR/Operator.h" | |||
| 109 | #include "llvm/IR/PatternMatch.h" | |||
| 110 | #include "llvm/IR/Type.h" | |||
| 111 | #include "llvm/IR/Use.h" | |||
| 112 | #include "llvm/IR/User.h" | |||
| 113 | #include "llvm/IR/Value.h" | |||
| 114 | #include "llvm/IR/Verifier.h" | |||
| 115 | #include "llvm/InitializePasses.h" | |||
| 116 | #include "llvm/Pass.h" | |||
| 117 | #include "llvm/Support/Casting.h" | |||
| 118 | #include "llvm/Support/CommandLine.h" | |||
| 119 | #include "llvm/Support/Compiler.h" | |||
| 120 | #include "llvm/Support/Debug.h" | |||
| 121 | #include "llvm/Support/ErrorHandling.h" | |||
| 122 | #include "llvm/Support/KnownBits.h" | |||
| 123 | #include "llvm/Support/SaveAndRestore.h" | |||
| 124 | #include "llvm/Support/raw_ostream.h" | |||
| 125 | #include <algorithm> | |||
| 126 | #include <cassert> | |||
| 127 | #include <climits> | |||
| 128 | #include <cstddef> | |||
| 129 | #include <cstdint> | |||
| 130 | #include <cstdlib> | |||
| 131 | #include <map> | |||
| 132 | #include <memory> | |||
| 133 | #include <tuple> | |||
| 134 | #include <utility> | |||
| 135 | #include <vector> | |||
| 136 | ||||
| 137 | using namespace llvm; | |||
| 138 | using namespace PatternMatch; | |||
| 139 | ||||
| 140 | #define DEBUG_TYPE"scalar-evolution" "scalar-evolution" | |||
| 141 | ||||
| 142 | STATISTIC(NumArrayLenItCounts,static llvm::Statistic NumArrayLenItCounts = {"scalar-evolution" , "NumArrayLenItCounts", "Number of trip counts computed with array length" } | |||
| 143 | "Number of trip counts computed with array length")static llvm::Statistic NumArrayLenItCounts = {"scalar-evolution" , "NumArrayLenItCounts", "Number of trip counts computed with array length" }; | |||
| 144 | STATISTIC(NumTripCountsComputed,static llvm::Statistic NumTripCountsComputed = {"scalar-evolution" , "NumTripCountsComputed", "Number of loops with predictable loop counts" } | |||
| 145 | "Number of loops with predictable loop counts")static llvm::Statistic NumTripCountsComputed = {"scalar-evolution" , "NumTripCountsComputed", "Number of loops with predictable loop counts" }; | |||
| 146 | STATISTIC(NumTripCountsNotComputed,static llvm::Statistic NumTripCountsNotComputed = {"scalar-evolution" , "NumTripCountsNotComputed", "Number of loops without predictable loop counts" } | |||
| 147 | "Number of loops without predictable loop counts")static llvm::Statistic NumTripCountsNotComputed = {"scalar-evolution" , "NumTripCountsNotComputed", "Number of loops without predictable loop counts" }; | |||
| 148 | STATISTIC(NumBruteForceTripCountsComputed,static llvm::Statistic NumBruteForceTripCountsComputed = {"scalar-evolution" , "NumBruteForceTripCountsComputed", "Number of loops with trip counts computed by force" } | |||
| 149 | "Number of loops with trip counts computed by force")static llvm::Statistic NumBruteForceTripCountsComputed = {"scalar-evolution" , "NumBruteForceTripCountsComputed", "Number of loops with trip counts computed by force" }; | |||
| 150 | ||||
| 151 | static cl::opt<unsigned> | |||
| 152 | MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden, | |||
| 153 | cl::ZeroOrMore, | |||
| 154 | cl::desc("Maximum number of iterations SCEV will " | |||
| 155 | "symbolically execute a constant " | |||
| 156 | "derived loop"), | |||
| 157 | cl::init(100)); | |||
| 158 | ||||
| 159 | // FIXME: Enable this with EXPENSIVE_CHECKS when the test suite is clean. | |||
| 160 | static cl::opt<bool> VerifySCEV( | |||
| 161 | "verify-scev", cl::Hidden, | |||
| 162 | cl::desc("Verify ScalarEvolution's backedge taken counts (slow)")); | |||
| 163 | static cl::opt<bool> VerifySCEVStrict( | |||
| 164 | "verify-scev-strict", cl::Hidden, | |||
| 165 | cl::desc("Enable stricter verification with -verify-scev is passed")); | |||
| 166 | static cl::opt<bool> | |||
| 167 | VerifySCEVMap("verify-scev-maps", cl::Hidden, | |||
| 168 | cl::desc("Verify no dangling value in ScalarEvolution's " | |||
| 169 | "ExprValueMap (slow)")); | |||
| 170 | ||||
| 171 | static cl::opt<bool> VerifyIR( | |||
| 172 | "scev-verify-ir", cl::Hidden, | |||
| 173 | cl::desc("Verify IR correctness when making sensitive SCEV queries (slow)"), | |||
| 174 | cl::init(false)); | |||
| 175 | ||||
| 176 | static cl::opt<unsigned> MulOpsInlineThreshold( | |||
| 177 | "scev-mulops-inline-threshold", cl::Hidden, | |||
| 178 | cl::desc("Threshold for inlining multiplication operands into a SCEV"), | |||
| 179 | cl::init(32)); | |||
| 180 | ||||
| 181 | static cl::opt<unsigned> AddOpsInlineThreshold( | |||
| 182 | "scev-addops-inline-threshold", cl::Hidden, | |||
| 183 | cl::desc("Threshold for inlining addition operands into a SCEV"), | |||
| 184 | cl::init(500)); | |||
| 185 | ||||
| 186 | static cl::opt<unsigned> MaxSCEVCompareDepth( | |||
| 187 | "scalar-evolution-max-scev-compare-depth", cl::Hidden, | |||
| 188 | cl::desc("Maximum depth of recursive SCEV complexity comparisons"), | |||
| 189 | cl::init(32)); | |||
| 190 | ||||
| 191 | static cl::opt<unsigned> MaxSCEVOperationsImplicationDepth( | |||
| 192 | "scalar-evolution-max-scev-operations-implication-depth", cl::Hidden, | |||
| 193 | cl::desc("Maximum depth of recursive SCEV operations implication analysis"), | |||
| 194 | cl::init(2)); | |||
| 195 | ||||
| 196 | static cl::opt<unsigned> MaxValueCompareDepth( | |||
| 197 | "scalar-evolution-max-value-compare-depth", cl::Hidden, | |||
| 198 | cl::desc("Maximum depth of recursive value complexity comparisons"), | |||
| 199 | cl::init(2)); | |||
| 200 | ||||
| 201 | static cl::opt<unsigned> | |||
| 202 | MaxArithDepth("scalar-evolution-max-arith-depth", cl::Hidden, | |||
| 203 | cl::desc("Maximum depth of recursive arithmetics"), | |||
| 204 | cl::init(32)); | |||
| 205 | ||||
| 206 | static cl::opt<unsigned> MaxConstantEvolvingDepth( | |||
| 207 | "scalar-evolution-max-constant-evolving-depth", cl::Hidden, | |||
| 208 | cl::desc("Maximum depth of recursive constant evolving"), cl::init(32)); | |||
| 209 | ||||
| 210 | static cl::opt<unsigned> | |||
| 211 | MaxCastDepth("scalar-evolution-max-cast-depth", cl::Hidden, | |||
| 212 | cl::desc("Maximum depth of recursive SExt/ZExt/Trunc"), | |||
| 213 | cl::init(8)); | |||
| 214 | ||||
| 215 | static cl::opt<unsigned> | |||
| 216 | MaxAddRecSize("scalar-evolution-max-add-rec-size", cl::Hidden, | |||
| 217 | cl::desc("Max coefficients in AddRec during evolving"), | |||
| 218 | cl::init(8)); | |||
| 219 | ||||
| 220 | static cl::opt<unsigned> | |||
| 221 | HugeExprThreshold("scalar-evolution-huge-expr-threshold", cl::Hidden, | |||
| 222 | cl::desc("Size of the expression which is considered huge"), | |||
| 223 | cl::init(4096)); | |||
| 224 | ||||
| 225 | static cl::opt<bool> | |||
| 226 | ClassifyExpressions("scalar-evolution-classify-expressions", | |||
| 227 | cl::Hidden, cl::init(true), | |||
| 228 | cl::desc("When printing analysis, include information on every instruction")); | |||
| 229 | ||||
| 230 | static cl::opt<bool> UseExpensiveRangeSharpening( | |||
| 231 | "scalar-evolution-use-expensive-range-sharpening", cl::Hidden, | |||
| 232 | cl::init(false), | |||
| 233 | cl::desc("Use more powerful methods of sharpening expression ranges. May " | |||
| 234 | "be costly in terms of compile time")); | |||
| 235 | ||||
| 236 | //===----------------------------------------------------------------------===// | |||
| 237 | // SCEV class definitions | |||
| 238 | //===----------------------------------------------------------------------===// | |||
| 239 | ||||
| 240 | //===----------------------------------------------------------------------===// | |||
| 241 | // Implementation of the SCEV class. | |||
| 242 | // | |||
| 243 | ||||
| 244 | #if !defined(NDEBUG1) || defined(LLVM_ENABLE_DUMP) | |||
| 245 | LLVM_DUMP_METHOD__attribute__((noinline)) void SCEV::dump() const { | |||
| 246 | print(dbgs()); | |||
| 247 | dbgs() << '\n'; | |||
| 248 | } | |||
| 249 | #endif | |||
| 250 | ||||
| 251 | void SCEV::print(raw_ostream &OS) const { | |||
| 252 | switch (getSCEVType()) { | |||
| 253 | case scConstant: | |||
| 254 | cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false); | |||
| 255 | return; | |||
| 256 | case scPtrToInt: { | |||
| 257 | const SCEVPtrToIntExpr *PtrToInt = cast<SCEVPtrToIntExpr>(this); | |||
| 258 | const SCEV *Op = PtrToInt->getOperand(); | |||
| 259 | OS << "(ptrtoint " << *Op->getType() << " " << *Op << " to " | |||
| 260 | << *PtrToInt->getType() << ")"; | |||
| 261 | return; | |||
| 262 | } | |||
| 263 | case scTruncate: { | |||
| 264 | const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this); | |||
| 265 | const SCEV *Op = Trunc->getOperand(); | |||
| 266 | OS << "(trunc " << *Op->getType() << " " << *Op << " to " | |||
| 267 | << *Trunc->getType() << ")"; | |||
| 268 | return; | |||
| 269 | } | |||
| 270 | case scZeroExtend: { | |||
| 271 | const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this); | |||
| 272 | const SCEV *Op = ZExt->getOperand(); | |||
| 273 | OS << "(zext " << *Op->getType() << " " << *Op << " to " | |||
| 274 | << *ZExt->getType() << ")"; | |||
| 275 | return; | |||
| 276 | } | |||
| 277 | case scSignExtend: { | |||
| 278 | const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this); | |||
| 279 | const SCEV *Op = SExt->getOperand(); | |||
| 280 | OS << "(sext " << *Op->getType() << " " << *Op << " to " | |||
| 281 | << *SExt->getType() << ")"; | |||
| 282 | return; | |||
| 283 | } | |||
| 284 | case scAddRecExpr: { | |||
| 285 | const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this); | |||
| 286 | OS << "{" << *AR->getOperand(0); | |||
| 287 | for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i) | |||
| 288 | OS << ",+," << *AR->getOperand(i); | |||
| 289 | OS << "}<"; | |||
| 290 | if (AR->hasNoUnsignedWrap()) | |||
| 291 | OS << "nuw><"; | |||
| 292 | if (AR->hasNoSignedWrap()) | |||
| 293 | OS << "nsw><"; | |||
| 294 | if (AR->hasNoSelfWrap() && | |||
| 295 | !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW))) | |||
| 296 | OS << "nw><"; | |||
| 297 | AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 298 | OS << ">"; | |||
| 299 | return; | |||
| 300 | } | |||
| 301 | case scAddExpr: | |||
| 302 | case scMulExpr: | |||
| 303 | case scUMaxExpr: | |||
| 304 | case scSMaxExpr: | |||
| 305 | case scUMinExpr: | |||
| 306 | case scSMinExpr: { | |||
| 307 | const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this); | |||
| 308 | const char *OpStr = nullptr; | |||
| 309 | switch (NAry->getSCEVType()) { | |||
| 310 | case scAddExpr: OpStr = " + "; break; | |||
| 311 | case scMulExpr: OpStr = " * "; break; | |||
| 312 | case scUMaxExpr: OpStr = " umax "; break; | |||
| 313 | case scSMaxExpr: OpStr = " smax "; break; | |||
| 314 | case scUMinExpr: | |||
| 315 | OpStr = " umin "; | |||
| 316 | break; | |||
| 317 | case scSMinExpr: | |||
| 318 | OpStr = " smin "; | |||
| 319 | break; | |||
| 320 | default: | |||
| 321 | llvm_unreachable("There are no other nary expression types.")__builtin_unreachable(); | |||
| 322 | } | |||
| 323 | OS << "("; | |||
| 324 | ListSeparator LS(OpStr); | |||
| 325 | for (const SCEV *Op : NAry->operands()) | |||
| 326 | OS << LS << *Op; | |||
| 327 | OS << ")"; | |||
| 328 | switch (NAry->getSCEVType()) { | |||
| 329 | case scAddExpr: | |||
| 330 | case scMulExpr: | |||
| 331 | if (NAry->hasNoUnsignedWrap()) | |||
| 332 | OS << "<nuw>"; | |||
| 333 | if (NAry->hasNoSignedWrap()) | |||
| 334 | OS << "<nsw>"; | |||
| 335 | break; | |||
| 336 | default: | |||
| 337 | // Nothing to print for other nary expressions. | |||
| 338 | break; | |||
| 339 | } | |||
| 340 | return; | |||
| 341 | } | |||
| 342 | case scUDivExpr: { | |||
| 343 | const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this); | |||
| 344 | OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")"; | |||
| 345 | return; | |||
| 346 | } | |||
| 347 | case scUnknown: { | |||
| 348 | const SCEVUnknown *U = cast<SCEVUnknown>(this); | |||
| 349 | Type *AllocTy; | |||
| 350 | if (U->isSizeOf(AllocTy)) { | |||
| 351 | OS << "sizeof(" << *AllocTy << ")"; | |||
| 352 | return; | |||
| 353 | } | |||
| 354 | if (U->isAlignOf(AllocTy)) { | |||
| 355 | OS << "alignof(" << *AllocTy << ")"; | |||
| 356 | return; | |||
| 357 | } | |||
| 358 | ||||
| 359 | Type *CTy; | |||
| 360 | Constant *FieldNo; | |||
| 361 | if (U->isOffsetOf(CTy, FieldNo)) { | |||
| 362 | OS << "offsetof(" << *CTy << ", "; | |||
| 363 | FieldNo->printAsOperand(OS, false); | |||
| 364 | OS << ")"; | |||
| 365 | return; | |||
| 366 | } | |||
| 367 | ||||
| 368 | // Otherwise just print it normally. | |||
| 369 | U->getValue()->printAsOperand(OS, false); | |||
| 370 | return; | |||
| 371 | } | |||
| 372 | case scCouldNotCompute: | |||
| 373 | OS << "***COULDNOTCOMPUTE***"; | |||
| 374 | return; | |||
| 375 | } | |||
| 376 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 377 | } | |||
| 378 | ||||
| 379 | Type *SCEV::getType() const { | |||
| 380 | switch (getSCEVType()) { | |||
| 381 | case scConstant: | |||
| 382 | return cast<SCEVConstant>(this)->getType(); | |||
| 383 | case scPtrToInt: | |||
| 384 | case scTruncate: | |||
| 385 | case scZeroExtend: | |||
| 386 | case scSignExtend: | |||
| 387 | return cast<SCEVCastExpr>(this)->getType(); | |||
| 388 | case scAddRecExpr: | |||
| 389 | return cast<SCEVAddRecExpr>(this)->getType(); | |||
| 390 | case scMulExpr: | |||
| 391 | return cast<SCEVMulExpr>(this)->getType(); | |||
| 392 | case scUMaxExpr: | |||
| 393 | case scSMaxExpr: | |||
| 394 | case scUMinExpr: | |||
| 395 | case scSMinExpr: | |||
| 396 | return cast<SCEVMinMaxExpr>(this)->getType(); | |||
| 397 | case scAddExpr: | |||
| 398 | return cast<SCEVAddExpr>(this)->getType(); | |||
| 399 | case scUDivExpr: | |||
| 400 | return cast<SCEVUDivExpr>(this)->getType(); | |||
| 401 | case scUnknown: | |||
| 402 | return cast<SCEVUnknown>(this)->getType(); | |||
| 403 | case scCouldNotCompute: | |||
| 404 | llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")__builtin_unreachable(); | |||
| 405 | } | |||
| 406 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 407 | } | |||
| 408 | ||||
| 409 | bool SCEV::isZero() const { | |||
| 410 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this)) | |||
| 411 | return SC->getValue()->isZero(); | |||
| 412 | return false; | |||
| 413 | } | |||
| 414 | ||||
| 415 | bool SCEV::isOne() const { | |||
| 416 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this)) | |||
| 417 | return SC->getValue()->isOne(); | |||
| 418 | return false; | |||
| 419 | } | |||
| 420 | ||||
| 421 | bool SCEV::isAllOnesValue() const { | |||
| 422 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this)) | |||
| 423 | return SC->getValue()->isMinusOne(); | |||
| 424 | return false; | |||
| 425 | } | |||
| 426 | ||||
| 427 | bool SCEV::isNonConstantNegative() const { | |||
| 428 | const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this); | |||
| 429 | if (!Mul) return false; | |||
| 430 | ||||
| 431 | // If there is a constant factor, it will be first. | |||
| 432 | const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0)); | |||
| 433 | if (!SC) return false; | |||
| 434 | ||||
| 435 | // Return true if the value is negative, this matches things like (-42 * V). | |||
| 436 | return SC->getAPInt().isNegative(); | |||
| 437 | } | |||
| 438 | ||||
| 439 | SCEVCouldNotCompute::SCEVCouldNotCompute() : | |||
| 440 | SCEV(FoldingSetNodeIDRef(), scCouldNotCompute, 0) {} | |||
| 441 | ||||
| 442 | bool SCEVCouldNotCompute::classof(const SCEV *S) { | |||
| 443 | return S->getSCEVType() == scCouldNotCompute; | |||
| 444 | } | |||
| 445 | ||||
| 446 | const SCEV *ScalarEvolution::getConstant(ConstantInt *V) { | |||
| 447 | FoldingSetNodeID ID; | |||
| 448 | ID.AddInteger(scConstant); | |||
| 449 | ID.AddPointer(V); | |||
| 450 | void *IP = nullptr; | |||
| 451 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 452 | SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V); | |||
| 453 | UniqueSCEVs.InsertNode(S, IP); | |||
| 454 | return S; | |||
| 455 | } | |||
| 456 | ||||
| 457 | const SCEV *ScalarEvolution::getConstant(const APInt &Val) { | |||
| 458 | return getConstant(ConstantInt::get(getContext(), Val)); | |||
| 459 | } | |||
| 460 | ||||
| 461 | const SCEV * | |||
| 462 | ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) { | |||
| 463 | IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty)); | |||
| 464 | return getConstant(ConstantInt::get(ITy, V, isSigned)); | |||
| 465 | } | |||
| 466 | ||||
| 467 | SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, | |||
| 468 | const SCEV *op, Type *ty) | |||
| 469 | : SCEV(ID, SCEVTy, computeExpressionSize(op)), Ty(ty) { | |||
| 470 | Operands[0] = op; | |||
| 471 | } | |||
| 472 | ||||
| 473 | SCEVPtrToIntExpr::SCEVPtrToIntExpr(const FoldingSetNodeIDRef ID, const SCEV *Op, | |||
| 474 | Type *ITy) | |||
| 475 | : SCEVCastExpr(ID, scPtrToInt, Op, ITy) { | |||
| 476 | assert(getOperand()->getType()->isPointerTy() && Ty->isIntegerTy() &&((void)0) | |||
| 477 | "Must be a non-bit-width-changing pointer-to-integer cast!")((void)0); | |||
| 478 | } | |||
| 479 | ||||
| 480 | SCEVIntegralCastExpr::SCEVIntegralCastExpr(const FoldingSetNodeIDRef ID, | |||
| 481 | SCEVTypes SCEVTy, const SCEV *op, | |||
| 482 | Type *ty) | |||
| 483 | : SCEVCastExpr(ID, SCEVTy, op, ty) {} | |||
| 484 | ||||
| 485 | SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID, const SCEV *op, | |||
| 486 | Type *ty) | |||
| 487 | : SCEVIntegralCastExpr(ID, scTruncate, op, ty) { | |||
| 488 | assert(getOperand()->getType()->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 489 | "Cannot truncate non-integer value!")((void)0); | |||
| 490 | } | |||
| 491 | ||||
| 492 | SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID, | |||
| 493 | const SCEV *op, Type *ty) | |||
| 494 | : SCEVIntegralCastExpr(ID, scZeroExtend, op, ty) { | |||
| 495 | assert(getOperand()->getType()->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 496 | "Cannot zero extend non-integer value!")((void)0); | |||
| 497 | } | |||
| 498 | ||||
| 499 | SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID, | |||
| 500 | const SCEV *op, Type *ty) | |||
| 501 | : SCEVIntegralCastExpr(ID, scSignExtend, op, ty) { | |||
| 502 | assert(getOperand()->getType()->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 503 | "Cannot sign extend non-integer value!")((void)0); | |||
| 504 | } | |||
| 505 | ||||
| 506 | void SCEVUnknown::deleted() { | |||
| 507 | // Clear this SCEVUnknown from various maps. | |||
| 508 | SE->forgetMemoizedResults(this); | |||
| 509 | ||||
| 510 | // Remove this SCEVUnknown from the uniquing map. | |||
| 511 | SE->UniqueSCEVs.RemoveNode(this); | |||
| 512 | ||||
| 513 | // Release the value. | |||
| 514 | setValPtr(nullptr); | |||
| 515 | } | |||
| 516 | ||||
| 517 | void SCEVUnknown::allUsesReplacedWith(Value *New) { | |||
| 518 | // Remove this SCEVUnknown from the uniquing map. | |||
| 519 | SE->UniqueSCEVs.RemoveNode(this); | |||
| 520 | ||||
| 521 | // Update this SCEVUnknown to point to the new value. This is needed | |||
| 522 | // because there may still be outstanding SCEVs which still point to | |||
| 523 | // this SCEVUnknown. | |||
| 524 | setValPtr(New); | |||
| 525 | } | |||
| 526 | ||||
| 527 | bool SCEVUnknown::isSizeOf(Type *&AllocTy) const { | |||
| 528 | if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue())) | |||
| 529 | if (VCE->getOpcode() == Instruction::PtrToInt) | |||
| 530 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0))) | |||
| 531 | if (CE->getOpcode() == Instruction::GetElementPtr && | |||
| 532 | CE->getOperand(0)->isNullValue() && | |||
| 533 | CE->getNumOperands() == 2) | |||
| 534 | if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1))) | |||
| 535 | if (CI->isOne()) { | |||
| 536 | AllocTy = cast<GEPOperator>(CE)->getSourceElementType(); | |||
| 537 | return true; | |||
| 538 | } | |||
| 539 | ||||
| 540 | return false; | |||
| 541 | } | |||
| 542 | ||||
| 543 | bool SCEVUnknown::isAlignOf(Type *&AllocTy) const { | |||
| 544 | if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue())) | |||
| 545 | if (VCE->getOpcode() == Instruction::PtrToInt) | |||
| 546 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0))) | |||
| 547 | if (CE->getOpcode() == Instruction::GetElementPtr && | |||
| 548 | CE->getOperand(0)->isNullValue()) { | |||
| 549 | Type *Ty = cast<GEPOperator>(CE)->getSourceElementType(); | |||
| 550 | if (StructType *STy = dyn_cast<StructType>(Ty)) | |||
| 551 | if (!STy->isPacked() && | |||
| 552 | CE->getNumOperands() == 3 && | |||
| 553 | CE->getOperand(1)->isNullValue()) { | |||
| 554 | if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2))) | |||
| 555 | if (CI->isOne() && | |||
| 556 | STy->getNumElements() == 2 && | |||
| 557 | STy->getElementType(0)->isIntegerTy(1)) { | |||
| 558 | AllocTy = STy->getElementType(1); | |||
| 559 | return true; | |||
| 560 | } | |||
| 561 | } | |||
| 562 | } | |||
| 563 | ||||
| 564 | return false; | |||
| 565 | } | |||
| 566 | ||||
| 567 | bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const { | |||
| 568 | if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue())) | |||
| 569 | if (VCE->getOpcode() == Instruction::PtrToInt) | |||
| 570 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0))) | |||
| 571 | if (CE->getOpcode() == Instruction::GetElementPtr && | |||
| 572 | CE->getNumOperands() == 3 && | |||
| 573 | CE->getOperand(0)->isNullValue() && | |||
| 574 | CE->getOperand(1)->isNullValue()) { | |||
| 575 | Type *Ty = cast<GEPOperator>(CE)->getSourceElementType(); | |||
| 576 | // Ignore vector types here so that ScalarEvolutionExpander doesn't | |||
| 577 | // emit getelementptrs that index into vectors. | |||
| 578 | if (Ty->isStructTy() || Ty->isArrayTy()) { | |||
| 579 | CTy = Ty; | |||
| 580 | FieldNo = CE->getOperand(2); | |||
| 581 | return true; | |||
| 582 | } | |||
| 583 | } | |||
| 584 | ||||
| 585 | return false; | |||
| 586 | } | |||
| 587 | ||||
| 588 | //===----------------------------------------------------------------------===// | |||
| 589 | // SCEV Utilities | |||
| 590 | //===----------------------------------------------------------------------===// | |||
| 591 | ||||
| 592 | /// Compare the two values \p LV and \p RV in terms of their "complexity" where | |||
| 593 | /// "complexity" is a partial (and somewhat ad-hoc) relation used to order | |||
| 594 | /// operands in SCEV expressions. \p EqCache is a set of pairs of values that | |||
| 595 | /// have been previously deemed to be "equally complex" by this routine. It is | |||
| 596 | /// intended to avoid exponential time complexity in cases like: | |||
| 597 | /// | |||
| 598 | /// %a = f(%x, %y) | |||
| 599 | /// %b = f(%a, %a) | |||
| 600 | /// %c = f(%b, %b) | |||
| 601 | /// | |||
| 602 | /// %d = f(%x, %y) | |||
| 603 | /// %e = f(%d, %d) | |||
| 604 | /// %f = f(%e, %e) | |||
| 605 | /// | |||
| 606 | /// CompareValueComplexity(%f, %c) | |||
| 607 | /// | |||
| 608 | /// Since we do not continue running this routine on expression trees once we | |||
| 609 | /// have seen unequal values, there is no need to track them in the cache. | |||
| 610 | static int | |||
| 611 | CompareValueComplexity(EquivalenceClasses<const Value *> &EqCacheValue, | |||
| 612 | const LoopInfo *const LI, Value *LV, Value *RV, | |||
| 613 | unsigned Depth) { | |||
| 614 | if (Depth > MaxValueCompareDepth || EqCacheValue.isEquivalent(LV, RV)) | |||
| 615 | return 0; | |||
| 616 | ||||
| 617 | // Order pointer values after integer values. This helps SCEVExpander form | |||
| 618 | // GEPs. | |||
| 619 | bool LIsPointer = LV->getType()->isPointerTy(), | |||
| 620 | RIsPointer = RV->getType()->isPointerTy(); | |||
| 621 | if (LIsPointer != RIsPointer) | |||
| 622 | return (int)LIsPointer - (int)RIsPointer; | |||
| 623 | ||||
| 624 | // Compare getValueID values. | |||
| 625 | unsigned LID = LV->getValueID(), RID = RV->getValueID(); | |||
| 626 | if (LID != RID) | |||
| 627 | return (int)LID - (int)RID; | |||
| 628 | ||||
| 629 | // Sort arguments by their position. | |||
| 630 | if (const auto *LA = dyn_cast<Argument>(LV)) { | |||
| 631 | const auto *RA = cast<Argument>(RV); | |||
| 632 | unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo(); | |||
| 633 | return (int)LArgNo - (int)RArgNo; | |||
| 634 | } | |||
| 635 | ||||
| 636 | if (const auto *LGV = dyn_cast<GlobalValue>(LV)) { | |||
| 637 | const auto *RGV = cast<GlobalValue>(RV); | |||
| 638 | ||||
| 639 | const auto IsGVNameSemantic = [&](const GlobalValue *GV) { | |||
| 640 | auto LT = GV->getLinkage(); | |||
| 641 | return !(GlobalValue::isPrivateLinkage(LT) || | |||
| 642 | GlobalValue::isInternalLinkage(LT)); | |||
| 643 | }; | |||
| 644 | ||||
| 645 | // Use the names to distinguish the two values, but only if the | |||
| 646 | // names are semantically important. | |||
| 647 | if (IsGVNameSemantic(LGV) && IsGVNameSemantic(RGV)) | |||
| 648 | return LGV->getName().compare(RGV->getName()); | |||
| 649 | } | |||
| 650 | ||||
| 651 | // For instructions, compare their loop depth, and their operand count. This | |||
| 652 | // is pretty loose. | |||
| 653 | if (const auto *LInst = dyn_cast<Instruction>(LV)) { | |||
| 654 | const auto *RInst = cast<Instruction>(RV); | |||
| 655 | ||||
| 656 | // Compare loop depths. | |||
| 657 | const BasicBlock *LParent = LInst->getParent(), | |||
| 658 | *RParent = RInst->getParent(); | |||
| 659 | if (LParent != RParent) { | |||
| 660 | unsigned LDepth = LI->getLoopDepth(LParent), | |||
| 661 | RDepth = LI->getLoopDepth(RParent); | |||
| 662 | if (LDepth != RDepth) | |||
| 663 | return (int)LDepth - (int)RDepth; | |||
| 664 | } | |||
| 665 | ||||
| 666 | // Compare the number of operands. | |||
| 667 | unsigned LNumOps = LInst->getNumOperands(), | |||
| 668 | RNumOps = RInst->getNumOperands(); | |||
| 669 | if (LNumOps != RNumOps) | |||
| 670 | return (int)LNumOps - (int)RNumOps; | |||
| 671 | ||||
| 672 | for (unsigned Idx : seq(0u, LNumOps)) { | |||
| 673 | int Result = | |||
| 674 | CompareValueComplexity(EqCacheValue, LI, LInst->getOperand(Idx), | |||
| 675 | RInst->getOperand(Idx), Depth + 1); | |||
| 676 | if (Result != 0) | |||
| 677 | return Result; | |||
| 678 | } | |||
| 679 | } | |||
| 680 | ||||
| 681 | EqCacheValue.unionSets(LV, RV); | |||
| 682 | return 0; | |||
| 683 | } | |||
| 684 | ||||
| 685 | // Return negative, zero, or positive, if LHS is less than, equal to, or greater | |||
| 686 | // than RHS, respectively. A three-way result allows recursive comparisons to be | |||
| 687 | // more efficient. | |||
| 688 | // If the max analysis depth was reached, return None, assuming we do not know | |||
| 689 | // if they are equivalent for sure. | |||
| 690 | static Optional<int> | |||
| 691 | CompareSCEVComplexity(EquivalenceClasses<const SCEV *> &EqCacheSCEV, | |||
| 692 | EquivalenceClasses<const Value *> &EqCacheValue, | |||
| 693 | const LoopInfo *const LI, const SCEV *LHS, | |||
| 694 | const SCEV *RHS, DominatorTree &DT, unsigned Depth = 0) { | |||
| 695 | // Fast-path: SCEVs are uniqued so we can do a quick equality check. | |||
| 696 | if (LHS == RHS) | |||
| 697 | return 0; | |||
| 698 | ||||
| 699 | // Primarily, sort the SCEVs by their getSCEVType(). | |||
| 700 | SCEVTypes LType = LHS->getSCEVType(), RType = RHS->getSCEVType(); | |||
| 701 | if (LType != RType) | |||
| 702 | return (int)LType - (int)RType; | |||
| 703 | ||||
| 704 | if (EqCacheSCEV.isEquivalent(LHS, RHS)) | |||
| 705 | return 0; | |||
| 706 | ||||
| 707 | if (Depth > MaxSCEVCompareDepth) | |||
| 708 | return None; | |||
| 709 | ||||
| 710 | // Aside from the getSCEVType() ordering, the particular ordering | |||
| 711 | // isn't very important except that it's beneficial to be consistent, | |||
| 712 | // so that (a + b) and (b + a) don't end up as different expressions. | |||
| 713 | switch (LType) { | |||
| 714 | case scUnknown: { | |||
| 715 | const SCEVUnknown *LU = cast<SCEVUnknown>(LHS); | |||
| 716 | const SCEVUnknown *RU = cast<SCEVUnknown>(RHS); | |||
| 717 | ||||
| 718 | int X = CompareValueComplexity(EqCacheValue, LI, LU->getValue(), | |||
| 719 | RU->getValue(), Depth + 1); | |||
| 720 | if (X == 0) | |||
| 721 | EqCacheSCEV.unionSets(LHS, RHS); | |||
| 722 | return X; | |||
| 723 | } | |||
| 724 | ||||
| 725 | case scConstant: { | |||
| 726 | const SCEVConstant *LC = cast<SCEVConstant>(LHS); | |||
| 727 | const SCEVConstant *RC = cast<SCEVConstant>(RHS); | |||
| 728 | ||||
| 729 | // Compare constant values. | |||
| 730 | const APInt &LA = LC->getAPInt(); | |||
| 731 | const APInt &RA = RC->getAPInt(); | |||
| 732 | unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth(); | |||
| 733 | if (LBitWidth != RBitWidth) | |||
| 734 | return (int)LBitWidth - (int)RBitWidth; | |||
| 735 | return LA.ult(RA) ? -1 : 1; | |||
| 736 | } | |||
| 737 | ||||
| 738 | case scAddRecExpr: { | |||
| 739 | const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS); | |||
| 740 | const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS); | |||
| 741 | ||||
| 742 | // There is always a dominance between two recs that are used by one SCEV, | |||
| 743 | // so we can safely sort recs by loop header dominance. We require such | |||
| 744 | // order in getAddExpr. | |||
| 745 | const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop(); | |||
| 746 | if (LLoop != RLoop) { | |||
| 747 | const BasicBlock *LHead = LLoop->getHeader(), *RHead = RLoop->getHeader(); | |||
| 748 | assert(LHead != RHead && "Two loops share the same header?")((void)0); | |||
| 749 | if (DT.dominates(LHead, RHead)) | |||
| 750 | return 1; | |||
| 751 | else | |||
| 752 | assert(DT.dominates(RHead, LHead) &&((void)0) | |||
| 753 | "No dominance between recurrences used by one SCEV?")((void)0); | |||
| 754 | return -1; | |||
| 755 | } | |||
| 756 | ||||
| 757 | // Addrec complexity grows with operand count. | |||
| 758 | unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands(); | |||
| 759 | if (LNumOps != RNumOps) | |||
| 760 | return (int)LNumOps - (int)RNumOps; | |||
| 761 | ||||
| 762 | // Lexicographically compare. | |||
| 763 | for (unsigned i = 0; i != LNumOps; ++i) { | |||
| 764 | auto X = CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, | |||
| 765 | LA->getOperand(i), RA->getOperand(i), DT, | |||
| 766 | Depth + 1); | |||
| 767 | if (X != 0) | |||
| 768 | return X; | |||
| 769 | } | |||
| 770 | EqCacheSCEV.unionSets(LHS, RHS); | |||
| 771 | return 0; | |||
| 772 | } | |||
| 773 | ||||
| 774 | case scAddExpr: | |||
| 775 | case scMulExpr: | |||
| 776 | case scSMaxExpr: | |||
| 777 | case scUMaxExpr: | |||
| 778 | case scSMinExpr: | |||
| 779 | case scUMinExpr: { | |||
| 780 | const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS); | |||
| 781 | const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS); | |||
| 782 | ||||
| 783 | // Lexicographically compare n-ary expressions. | |||
| 784 | unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands(); | |||
| 785 | if (LNumOps != RNumOps) | |||
| 786 | return (int)LNumOps - (int)RNumOps; | |||
| 787 | ||||
| 788 | for (unsigned i = 0; i != LNumOps; ++i) { | |||
| 789 | auto X = CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, | |||
| 790 | LC->getOperand(i), RC->getOperand(i), DT, | |||
| 791 | Depth + 1); | |||
| 792 | if (X != 0) | |||
| 793 | return X; | |||
| 794 | } | |||
| 795 | EqCacheSCEV.unionSets(LHS, RHS); | |||
| 796 | return 0; | |||
| 797 | } | |||
| 798 | ||||
| 799 | case scUDivExpr: { | |||
| 800 | const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS); | |||
| 801 | const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS); | |||
| 802 | ||||
| 803 | // Lexicographically compare udiv expressions. | |||
| 804 | auto X = CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, LC->getLHS(), | |||
| 805 | RC->getLHS(), DT, Depth + 1); | |||
| 806 | if (X != 0) | |||
| 807 | return X; | |||
| 808 | X = CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, LC->getRHS(), | |||
| 809 | RC->getRHS(), DT, Depth + 1); | |||
| 810 | if (X == 0) | |||
| 811 | EqCacheSCEV.unionSets(LHS, RHS); | |||
| 812 | return X; | |||
| 813 | } | |||
| 814 | ||||
| 815 | case scPtrToInt: | |||
| 816 | case scTruncate: | |||
| 817 | case scZeroExtend: | |||
| 818 | case scSignExtend: { | |||
| 819 | const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS); | |||
| 820 | const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS); | |||
| 821 | ||||
| 822 | // Compare cast expressions by operand. | |||
| 823 | auto X = | |||
| 824 | CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, LC->getOperand(), | |||
| 825 | RC->getOperand(), DT, Depth + 1); | |||
| 826 | if (X == 0) | |||
| 827 | EqCacheSCEV.unionSets(LHS, RHS); | |||
| 828 | return X; | |||
| 829 | } | |||
| 830 | ||||
| 831 | case scCouldNotCompute: | |||
| 832 | llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")__builtin_unreachable(); | |||
| 833 | } | |||
| 834 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 835 | } | |||
| 836 | ||||
| 837 | /// Given a list of SCEV objects, order them by their complexity, and group | |||
| 838 | /// objects of the same complexity together by value. When this routine is | |||
| 839 | /// finished, we know that any duplicates in the vector are consecutive and that | |||
| 840 | /// complexity is monotonically increasing. | |||
| 841 | /// | |||
| 842 | /// Note that we go take special precautions to ensure that we get deterministic | |||
| 843 | /// results from this routine. In other words, we don't want the results of | |||
| 844 | /// this to depend on where the addresses of various SCEV objects happened to | |||
| 845 | /// land in memory. | |||
| 846 | static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops, | |||
| 847 | LoopInfo *LI, DominatorTree &DT) { | |||
| 848 | if (Ops.size() < 2) return; // Noop | |||
| 849 | ||||
| 850 | EquivalenceClasses<const SCEV *> EqCacheSCEV; | |||
| 851 | EquivalenceClasses<const Value *> EqCacheValue; | |||
| 852 | ||||
| 853 | // Whether LHS has provably less complexity than RHS. | |||
| 854 | auto IsLessComplex = [&](const SCEV *LHS, const SCEV *RHS) { | |||
| 855 | auto Complexity = | |||
| 856 | CompareSCEVComplexity(EqCacheSCEV, EqCacheValue, LI, LHS, RHS, DT); | |||
| 857 | return Complexity && *Complexity < 0; | |||
| 858 | }; | |||
| 859 | if (Ops.size() == 2) { | |||
| 860 | // This is the common case, which also happens to be trivially simple. | |||
| 861 | // Special case it. | |||
| 862 | const SCEV *&LHS = Ops[0], *&RHS = Ops[1]; | |||
| 863 | if (IsLessComplex(RHS, LHS)) | |||
| 864 | std::swap(LHS, RHS); | |||
| 865 | return; | |||
| 866 | } | |||
| 867 | ||||
| 868 | // Do the rough sort by complexity. | |||
| 869 | llvm::stable_sort(Ops, [&](const SCEV *LHS, const SCEV *RHS) { | |||
| 870 | return IsLessComplex(LHS, RHS); | |||
| 871 | }); | |||
| 872 | ||||
| 873 | // Now that we are sorted by complexity, group elements of the same | |||
| 874 | // complexity. Note that this is, at worst, N^2, but the vector is likely to | |||
| 875 | // be extremely short in practice. Note that we take this approach because we | |||
| 876 | // do not want to depend on the addresses of the objects we are grouping. | |||
| 877 | for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) { | |||
| 878 | const SCEV *S = Ops[i]; | |||
| 879 | unsigned Complexity = S->getSCEVType(); | |||
| 880 | ||||
| 881 | // If there are any objects of the same complexity and same value as this | |||
| 882 | // one, group them. | |||
| 883 | for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) { | |||
| 884 | if (Ops[j] == S) { // Found a duplicate. | |||
| 885 | // Move it to immediately after i'th element. | |||
| 886 | std::swap(Ops[i+1], Ops[j]); | |||
| 887 | ++i; // no need to rescan it. | |||
| 888 | if (i == e-2) return; // Done! | |||
| 889 | } | |||
| 890 | } | |||
| 891 | } | |||
| 892 | } | |||
| 893 | ||||
| 894 | /// Returns true if \p Ops contains a huge SCEV (the subtree of S contains at | |||
| 895 | /// least HugeExprThreshold nodes). | |||
| 896 | static bool hasHugeExpression(ArrayRef<const SCEV *> Ops) { | |||
| 897 | return any_of(Ops, [](const SCEV *S) { | |||
| 898 | return S->getExpressionSize() >= HugeExprThreshold; | |||
| 899 | }); | |||
| 900 | } | |||
| 901 | ||||
| 902 | //===----------------------------------------------------------------------===// | |||
| 903 | // Simple SCEV method implementations | |||
| 904 | //===----------------------------------------------------------------------===// | |||
| 905 | ||||
| 906 | /// Compute BC(It, K). The result has width W. Assume, K > 0. | |||
| 907 | static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K, | |||
| 908 | ScalarEvolution &SE, | |||
| 909 | Type *ResultTy) { | |||
| 910 | // Handle the simplest case efficiently. | |||
| 911 | if (K == 1) | |||
| 912 | return SE.getTruncateOrZeroExtend(It, ResultTy); | |||
| 913 | ||||
| 914 | // We are using the following formula for BC(It, K): | |||
| 915 | // | |||
| 916 | // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K! | |||
| 917 | // | |||
| 918 | // Suppose, W is the bitwidth of the return value. We must be prepared for | |||
| 919 | // overflow. Hence, we must assure that the result of our computation is | |||
| 920 | // equal to the accurate one modulo 2^W. Unfortunately, division isn't | |||
| 921 | // safe in modular arithmetic. | |||
| 922 | // | |||
| 923 | // However, this code doesn't use exactly that formula; the formula it uses | |||
| 924 | // is something like the following, where T is the number of factors of 2 in | |||
| 925 | // K! (i.e. trailing zeros in the binary representation of K!), and ^ is | |||
| 926 | // exponentiation: | |||
| 927 | // | |||
| 928 | // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T) | |||
| 929 | // | |||
| 930 | // This formula is trivially equivalent to the previous formula. However, | |||
| 931 | // this formula can be implemented much more efficiently. The trick is that | |||
| 932 | // K! / 2^T is odd, and exact division by an odd number *is* safe in modular | |||
| 933 | // arithmetic. To do exact division in modular arithmetic, all we have | |||
| 934 | // to do is multiply by the inverse. Therefore, this step can be done at | |||
| 935 | // width W. | |||
| 936 | // | |||
| 937 | // The next issue is how to safely do the division by 2^T. The way this | |||
| 938 | // is done is by doing the multiplication step at a width of at least W + T | |||
| 939 | // bits. This way, the bottom W+T bits of the product are accurate. Then, | |||
| 940 | // when we perform the division by 2^T (which is equivalent to a right shift | |||
| 941 | // by T), the bottom W bits are accurate. Extra bits are okay; they'll get | |||
| 942 | // truncated out after the division by 2^T. | |||
| 943 | // | |||
| 944 | // In comparison to just directly using the first formula, this technique | |||
| 945 | // is much more efficient; using the first formula requires W * K bits, | |||
| 946 | // but this formula less than W + K bits. Also, the first formula requires | |||
| 947 | // a division step, whereas this formula only requires multiplies and shifts. | |||
| 948 | // | |||
| 949 | // It doesn't matter whether the subtraction step is done in the calculation | |||
| 950 | // width or the input iteration count's width; if the subtraction overflows, | |||
| 951 | // the result must be zero anyway. We prefer here to do it in the width of | |||
| 952 | // the induction variable because it helps a lot for certain cases; CodeGen | |||
| 953 | // isn't smart enough to ignore the overflow, which leads to much less | |||
| 954 | // efficient code if the width of the subtraction is wider than the native | |||
| 955 | // register width. | |||
| 956 | // | |||
| 957 | // (It's possible to not widen at all by pulling out factors of 2 before | |||
| 958 | // the multiplication; for example, K=2 can be calculated as | |||
| 959 | // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires | |||
| 960 | // extra arithmetic, so it's not an obvious win, and it gets | |||
| 961 | // much more complicated for K > 3.) | |||
| 962 | ||||
| 963 | // Protection from insane SCEVs; this bound is conservative, | |||
| 964 | // but it probably doesn't matter. | |||
| 965 | if (K > 1000) | |||
| 966 | return SE.getCouldNotCompute(); | |||
| 967 | ||||
| 968 | unsigned W = SE.getTypeSizeInBits(ResultTy); | |||
| 969 | ||||
| 970 | // Calculate K! / 2^T and T; we divide out the factors of two before | |||
| 971 | // multiplying for calculating K! / 2^T to avoid overflow. | |||
| 972 | // Other overflow doesn't matter because we only care about the bottom | |||
| 973 | // W bits of the result. | |||
| 974 | APInt OddFactorial(W, 1); | |||
| 975 | unsigned T = 1; | |||
| 976 | for (unsigned i = 3; i <= K; ++i) { | |||
| 977 | APInt Mult(W, i); | |||
| 978 | unsigned TwoFactors = Mult.countTrailingZeros(); | |||
| 979 | T += TwoFactors; | |||
| 980 | Mult.lshrInPlace(TwoFactors); | |||
| 981 | OddFactorial *= Mult; | |||
| 982 | } | |||
| 983 | ||||
| 984 | // We need at least W + T bits for the multiplication step | |||
| 985 | unsigned CalculationBits = W + T; | |||
| 986 | ||||
| 987 | // Calculate 2^T, at width T+W. | |||
| 988 | APInt DivFactor = APInt::getOneBitSet(CalculationBits, T); | |||
| 989 | ||||
| 990 | // Calculate the multiplicative inverse of K! / 2^T; | |||
| 991 | // this multiplication factor will perform the exact division by | |||
| 992 | // K! / 2^T. | |||
| 993 | APInt Mod = APInt::getSignedMinValue(W+1); | |||
| 994 | APInt MultiplyFactor = OddFactorial.zext(W+1); | |||
| 995 | MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod); | |||
| 996 | MultiplyFactor = MultiplyFactor.trunc(W); | |||
| 997 | ||||
| 998 | // Calculate the product, at width T+W | |||
| 999 | IntegerType *CalculationTy = IntegerType::get(SE.getContext(), | |||
| 1000 | CalculationBits); | |||
| 1001 | const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy); | |||
| 1002 | for (unsigned i = 1; i != K; ++i) { | |||
| 1003 | const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i)); | |||
| 1004 | Dividend = SE.getMulExpr(Dividend, | |||
| 1005 | SE.getTruncateOrZeroExtend(S, CalculationTy)); | |||
| 1006 | } | |||
| 1007 | ||||
| 1008 | // Divide by 2^T | |||
| 1009 | const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor)); | |||
| 1010 | ||||
| 1011 | // Truncate the result, and divide by K! / 2^T. | |||
| 1012 | ||||
| 1013 | return SE.getMulExpr(SE.getConstant(MultiplyFactor), | |||
| 1014 | SE.getTruncateOrZeroExtend(DivResult, ResultTy)); | |||
| 1015 | } | |||
| 1016 | ||||
| 1017 | /// Return the value of this chain of recurrences at the specified iteration | |||
| 1018 | /// number. We can evaluate this recurrence by multiplying each element in the | |||
| 1019 | /// chain by the binomial coefficient corresponding to it. In other words, we | |||
| 1020 | /// can evaluate {A,+,B,+,C,+,D} as: | |||
| 1021 | /// | |||
| 1022 | /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3) | |||
| 1023 | /// | |||
| 1024 | /// where BC(It, k) stands for binomial coefficient. | |||
| 1025 | const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It, | |||
| 1026 | ScalarEvolution &SE) const { | |||
| 1027 | return evaluateAtIteration(makeArrayRef(op_begin(), op_end()), It, SE); | |||
| 1028 | } | |||
| 1029 | ||||
| 1030 | const SCEV * | |||
| 1031 | SCEVAddRecExpr::evaluateAtIteration(ArrayRef<const SCEV *> Operands, | |||
| 1032 | const SCEV *It, ScalarEvolution &SE) { | |||
| 1033 | assert(Operands.size() > 0)((void)0); | |||
| 1034 | const SCEV *Result = Operands[0]; | |||
| 1035 | for (unsigned i = 1, e = Operands.size(); i != e; ++i) { | |||
| 1036 | // The computation is correct in the face of overflow provided that the | |||
| 1037 | // multiplication is performed _after_ the evaluation of the binomial | |||
| 1038 | // coefficient. | |||
| 1039 | const SCEV *Coeff = BinomialCoefficient(It, i, SE, Result->getType()); | |||
| 1040 | if (isa<SCEVCouldNotCompute>(Coeff)) | |||
| 1041 | return Coeff; | |||
| 1042 | ||||
| 1043 | Result = SE.getAddExpr(Result, SE.getMulExpr(Operands[i], Coeff)); | |||
| 1044 | } | |||
| 1045 | return Result; | |||
| 1046 | } | |||
| 1047 | ||||
| 1048 | //===----------------------------------------------------------------------===// | |||
| 1049 | // SCEV Expression folder implementations | |||
| 1050 | //===----------------------------------------------------------------------===// | |||
| 1051 | ||||
| 1052 | const SCEV *ScalarEvolution::getLosslessPtrToIntExpr(const SCEV *Op, | |||
| 1053 | unsigned Depth) { | |||
| 1054 | assert(Depth <= 1 &&((void)0) | |||
| 1055 | "getLosslessPtrToIntExpr() should self-recurse at most once.")((void)0); | |||
| 1056 | ||||
| 1057 | // We could be called with an integer-typed operands during SCEV rewrites. | |||
| 1058 | // Since the operand is an integer already, just perform zext/trunc/self cast. | |||
| 1059 | if (!Op->getType()->isPointerTy()) | |||
| 1060 | return Op; | |||
| 1061 | ||||
| 1062 | // What would be an ID for such a SCEV cast expression? | |||
| 1063 | FoldingSetNodeID ID; | |||
| 1064 | ID.AddInteger(scPtrToInt); | |||
| 1065 | ID.AddPointer(Op); | |||
| 1066 | ||||
| 1067 | void *IP = nullptr; | |||
| 1068 | ||||
| 1069 | // Is there already an expression for such a cast? | |||
| 1070 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) | |||
| 1071 | return S; | |||
| 1072 | ||||
| 1073 | // It isn't legal for optimizations to construct new ptrtoint expressions | |||
| 1074 | // for non-integral pointers. | |||
| 1075 | if (getDataLayout().isNonIntegralPointerType(Op->getType())) | |||
| 1076 | return getCouldNotCompute(); | |||
| 1077 | ||||
| 1078 | Type *IntPtrTy = getDataLayout().getIntPtrType(Op->getType()); | |||
| 1079 | ||||
| 1080 | // We can only trivially model ptrtoint if SCEV's effective (integer) type | |||
| 1081 | // is sufficiently wide to represent all possible pointer values. | |||
| 1082 | // We could theoretically teach SCEV to truncate wider pointers, but | |||
| 1083 | // that isn't implemented for now. | |||
| 1084 | if (getDataLayout().getTypeSizeInBits(getEffectiveSCEVType(Op->getType())) != | |||
| 1085 | getDataLayout().getTypeSizeInBits(IntPtrTy)) | |||
| 1086 | return getCouldNotCompute(); | |||
| 1087 | ||||
| 1088 | // If not, is this expression something we can't reduce any further? | |||
| 1089 | if (auto *U = dyn_cast<SCEVUnknown>(Op)) { | |||
| 1090 | // Perform some basic constant folding. If the operand of the ptr2int cast | |||
| 1091 | // is a null pointer, don't create a ptr2int SCEV expression (that will be | |||
| 1092 | // left as-is), but produce a zero constant. | |||
| 1093 | // NOTE: We could handle a more general case, but lack motivational cases. | |||
| 1094 | if (isa<ConstantPointerNull>(U->getValue())) | |||
| 1095 | return getZero(IntPtrTy); | |||
| 1096 | ||||
| 1097 | // Create an explicit cast node. | |||
| 1098 | // We can reuse the existing insert position since if we get here, | |||
| 1099 | // we won't have made any changes which would invalidate it. | |||
| 1100 | SCEV *S = new (SCEVAllocator) | |||
| 1101 | SCEVPtrToIntExpr(ID.Intern(SCEVAllocator), Op, IntPtrTy); | |||
| 1102 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1103 | addToLoopUseLists(S); | |||
| 1104 | return S; | |||
| 1105 | } | |||
| 1106 | ||||
| 1107 | assert(Depth == 0 && "getLosslessPtrToIntExpr() should not self-recurse for "((void)0) | |||
| 1108 | "non-SCEVUnknown's.")((void)0); | |||
| 1109 | ||||
| 1110 | // Otherwise, we've got some expression that is more complex than just a | |||
| 1111 | // single SCEVUnknown. But we don't want to have a SCEVPtrToIntExpr of an | |||
| 1112 | // arbitrary expression, we want to have SCEVPtrToIntExpr of an SCEVUnknown | |||
| 1113 | // only, and the expressions must otherwise be integer-typed. | |||
| 1114 | // So sink the cast down to the SCEVUnknown's. | |||
| 1115 | ||||
| 1116 | /// The SCEVPtrToIntSinkingRewriter takes a scalar evolution expression, | |||
| 1117 | /// which computes a pointer-typed value, and rewrites the whole expression | |||
| 1118 | /// tree so that *all* the computations are done on integers, and the only | |||
| 1119 | /// pointer-typed operands in the expression are SCEVUnknown. | |||
| 1120 | class SCEVPtrToIntSinkingRewriter | |||
| 1121 | : public SCEVRewriteVisitor<SCEVPtrToIntSinkingRewriter> { | |||
| 1122 | using Base = SCEVRewriteVisitor<SCEVPtrToIntSinkingRewriter>; | |||
| 1123 | ||||
| 1124 | public: | |||
| 1125 | SCEVPtrToIntSinkingRewriter(ScalarEvolution &SE) : SCEVRewriteVisitor(SE) {} | |||
| 1126 | ||||
| 1127 | static const SCEV *rewrite(const SCEV *Scev, ScalarEvolution &SE) { | |||
| 1128 | SCEVPtrToIntSinkingRewriter Rewriter(SE); | |||
| 1129 | return Rewriter.visit(Scev); | |||
| 1130 | } | |||
| 1131 | ||||
| 1132 | const SCEV *visit(const SCEV *S) { | |||
| 1133 | Type *STy = S->getType(); | |||
| 1134 | // If the expression is not pointer-typed, just keep it as-is. | |||
| 1135 | if (!STy->isPointerTy()) | |||
| 1136 | return S; | |||
| 1137 | // Else, recursively sink the cast down into it. | |||
| 1138 | return Base::visit(S); | |||
| 1139 | } | |||
| 1140 | ||||
| 1141 | const SCEV *visitAddExpr(const SCEVAddExpr *Expr) { | |||
| 1142 | SmallVector<const SCEV *, 2> Operands; | |||
| 1143 | bool Changed = false; | |||
| 1144 | for (auto *Op : Expr->operands()) { | |||
| 1145 | Operands.push_back(visit(Op)); | |||
| 1146 | Changed |= Op != Operands.back(); | |||
| 1147 | } | |||
| 1148 | return !Changed ? Expr : SE.getAddExpr(Operands, Expr->getNoWrapFlags()); | |||
| 1149 | } | |||
| 1150 | ||||
| 1151 | const SCEV *visitMulExpr(const SCEVMulExpr *Expr) { | |||
| 1152 | SmallVector<const SCEV *, 2> Operands; | |||
| 1153 | bool Changed = false; | |||
| 1154 | for (auto *Op : Expr->operands()) { | |||
| 1155 | Operands.push_back(visit(Op)); | |||
| 1156 | Changed |= Op != Operands.back(); | |||
| 1157 | } | |||
| 1158 | return !Changed ? Expr : SE.getMulExpr(Operands, Expr->getNoWrapFlags()); | |||
| 1159 | } | |||
| 1160 | ||||
| 1161 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 1162 | assert(Expr->getType()->isPointerTy() &&((void)0) | |||
| 1163 | "Should only reach pointer-typed SCEVUnknown's.")((void)0); | |||
| 1164 | return SE.getLosslessPtrToIntExpr(Expr, /*Depth=*/1); | |||
| 1165 | } | |||
| 1166 | }; | |||
| 1167 | ||||
| 1168 | // And actually perform the cast sinking. | |||
| 1169 | const SCEV *IntOp = SCEVPtrToIntSinkingRewriter::rewrite(Op, *this); | |||
| 1170 | assert(IntOp->getType()->isIntegerTy() &&((void)0) | |||
| 1171 | "We must have succeeded in sinking the cast, "((void)0) | |||
| 1172 | "and ending up with an integer-typed expression!")((void)0); | |||
| 1173 | return IntOp; | |||
| 1174 | } | |||
| 1175 | ||||
| 1176 | const SCEV *ScalarEvolution::getPtrToIntExpr(const SCEV *Op, Type *Ty) { | |||
| 1177 | assert(Ty->isIntegerTy() && "Target type must be an integer type!")((void)0); | |||
| 1178 | ||||
| 1179 | const SCEV *IntOp = getLosslessPtrToIntExpr(Op); | |||
| 1180 | if (isa<SCEVCouldNotCompute>(IntOp)) | |||
| 1181 | return IntOp; | |||
| 1182 | ||||
| 1183 | return getTruncateOrZeroExtend(IntOp, Ty); | |||
| 1184 | } | |||
| 1185 | ||||
| 1186 | const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op, Type *Ty, | |||
| 1187 | unsigned Depth) { | |||
| 1188 | assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&((void)0) | |||
| 1189 | "This is not a truncating conversion!")((void)0); | |||
| 1190 | assert(isSCEVable(Ty) &&((void)0) | |||
| 1191 | "This is not a conversion to a SCEVable type!")((void)0); | |||
| 1192 | assert(!Op->getType()->isPointerTy() && "Can't truncate pointer!")((void)0); | |||
| 1193 | Ty = getEffectiveSCEVType(Ty); | |||
| 1194 | ||||
| 1195 | FoldingSetNodeID ID; | |||
| 1196 | ID.AddInteger(scTruncate); | |||
| 1197 | ID.AddPointer(Op); | |||
| 1198 | ID.AddPointer(Ty); | |||
| 1199 | void *IP = nullptr; | |||
| 1200 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 1201 | ||||
| 1202 | // Fold if the operand is constant. | |||
| 1203 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) | |||
| 1204 | return getConstant( | |||
| 1205 | cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty))); | |||
| 1206 | ||||
| 1207 | // trunc(trunc(x)) --> trunc(x) | |||
| 1208 | if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) | |||
| 1209 | return getTruncateExpr(ST->getOperand(), Ty, Depth + 1); | |||
| 1210 | ||||
| 1211 | // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing | |||
| 1212 | if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op)) | |||
| 1213 | return getTruncateOrSignExtend(SS->getOperand(), Ty, Depth + 1); | |||
| 1214 | ||||
| 1215 | // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing | |||
| 1216 | if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op)) | |||
| 1217 | return getTruncateOrZeroExtend(SZ->getOperand(), Ty, Depth + 1); | |||
| 1218 | ||||
| 1219 | if (Depth > MaxCastDepth) { | |||
| 1220 | SCEV *S = | |||
| 1221 | new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator), Op, Ty); | |||
| 1222 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1223 | addToLoopUseLists(S); | |||
| 1224 | return S; | |||
| 1225 | } | |||
| 1226 | ||||
| 1227 | // trunc(x1 + ... + xN) --> trunc(x1) + ... + trunc(xN) and | |||
| 1228 | // trunc(x1 * ... * xN) --> trunc(x1) * ... * trunc(xN), | |||
| 1229 | // if after transforming we have at most one truncate, not counting truncates | |||
| 1230 | // that replace other casts. | |||
| 1231 | if (isa<SCEVAddExpr>(Op) || isa<SCEVMulExpr>(Op)) { | |||
| 1232 | auto *CommOp = cast<SCEVCommutativeExpr>(Op); | |||
| 1233 | SmallVector<const SCEV *, 4> Operands; | |||
| 1234 | unsigned numTruncs = 0; | |||
| 1235 | for (unsigned i = 0, e = CommOp->getNumOperands(); i != e && numTruncs < 2; | |||
| 1236 | ++i) { | |||
| 1237 | const SCEV *S = getTruncateExpr(CommOp->getOperand(i), Ty, Depth + 1); | |||
| 1238 | if (!isa<SCEVIntegralCastExpr>(CommOp->getOperand(i)) && | |||
| 1239 | isa<SCEVTruncateExpr>(S)) | |||
| 1240 | numTruncs++; | |||
| 1241 | Operands.push_back(S); | |||
| 1242 | } | |||
| 1243 | if (numTruncs < 2) { | |||
| 1244 | if (isa<SCEVAddExpr>(Op)) | |||
| 1245 | return getAddExpr(Operands); | |||
| 1246 | else if (isa<SCEVMulExpr>(Op)) | |||
| 1247 | return getMulExpr(Operands); | |||
| 1248 | else | |||
| 1249 | llvm_unreachable("Unexpected SCEV type for Op.")__builtin_unreachable(); | |||
| 1250 | } | |||
| 1251 | // Although we checked in the beginning that ID is not in the cache, it is | |||
| 1252 | // possible that during recursion and different modification ID was inserted | |||
| 1253 | // into the cache. So if we find it, just return it. | |||
| 1254 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) | |||
| 1255 | return S; | |||
| 1256 | } | |||
| 1257 | ||||
| 1258 | // If the input value is a chrec scev, truncate the chrec's operands. | |||
| 1259 | if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) { | |||
| 1260 | SmallVector<const SCEV *, 4> Operands; | |||
| 1261 | for (const SCEV *Op : AddRec->operands()) | |||
| 1262 | Operands.push_back(getTruncateExpr(Op, Ty, Depth + 1)); | |||
| 1263 | return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap); | |||
| 1264 | } | |||
| 1265 | ||||
| 1266 | // Return zero if truncating to known zeros. | |||
| 1267 | uint32_t MinTrailingZeros = GetMinTrailingZeros(Op); | |||
| 1268 | if (MinTrailingZeros >= getTypeSizeInBits(Ty)) | |||
| 1269 | return getZero(Ty); | |||
| 1270 | ||||
| 1271 | // The cast wasn't folded; create an explicit cast node. We can reuse | |||
| 1272 | // the existing insert position since if we get here, we won't have | |||
| 1273 | // made any changes which would invalidate it. | |||
| 1274 | SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator), | |||
| 1275 | Op, Ty); | |||
| 1276 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1277 | addToLoopUseLists(S); | |||
| 1278 | return S; | |||
| 1279 | } | |||
| 1280 | ||||
| 1281 | // Get the limit of a recurrence such that incrementing by Step cannot cause | |||
| 1282 | // signed overflow as long as the value of the recurrence within the | |||
| 1283 | // loop does not exceed this limit before incrementing. | |||
| 1284 | static const SCEV *getSignedOverflowLimitForStep(const SCEV *Step, | |||
| 1285 | ICmpInst::Predicate *Pred, | |||
| 1286 | ScalarEvolution *SE) { | |||
| 1287 | unsigned BitWidth = SE->getTypeSizeInBits(Step->getType()); | |||
| 1288 | if (SE->isKnownPositive(Step)) { | |||
| 1289 | *Pred = ICmpInst::ICMP_SLT; | |||
| 1290 | return SE->getConstant(APInt::getSignedMinValue(BitWidth) - | |||
| 1291 | SE->getSignedRangeMax(Step)); | |||
| 1292 | } | |||
| 1293 | if (SE->isKnownNegative(Step)) { | |||
| 1294 | *Pred = ICmpInst::ICMP_SGT; | |||
| 1295 | return SE->getConstant(APInt::getSignedMaxValue(BitWidth) - | |||
| 1296 | SE->getSignedRangeMin(Step)); | |||
| 1297 | } | |||
| 1298 | return nullptr; | |||
| 1299 | } | |||
| 1300 | ||||
| 1301 | // Get the limit of a recurrence such that incrementing by Step cannot cause | |||
| 1302 | // unsigned overflow as long as the value of the recurrence within the loop does | |||
| 1303 | // not exceed this limit before incrementing. | |||
| 1304 | static const SCEV *getUnsignedOverflowLimitForStep(const SCEV *Step, | |||
| 1305 | ICmpInst::Predicate *Pred, | |||
| 1306 | ScalarEvolution *SE) { | |||
| 1307 | unsigned BitWidth = SE->getTypeSizeInBits(Step->getType()); | |||
| 1308 | *Pred = ICmpInst::ICMP_ULT; | |||
| 1309 | ||||
| 1310 | return SE->getConstant(APInt::getMinValue(BitWidth) - | |||
| 1311 | SE->getUnsignedRangeMax(Step)); | |||
| 1312 | } | |||
| 1313 | ||||
| 1314 | namespace { | |||
| 1315 | ||||
| 1316 | struct ExtendOpTraitsBase { | |||
| 1317 | typedef const SCEV *(ScalarEvolution::*GetExtendExprTy)(const SCEV *, Type *, | |||
| 1318 | unsigned); | |||
| 1319 | }; | |||
| 1320 | ||||
| 1321 | // Used to make code generic over signed and unsigned overflow. | |||
| 1322 | template <typename ExtendOp> struct ExtendOpTraits { | |||
| 1323 | // Members present: | |||
| 1324 | // | |||
| 1325 | // static const SCEV::NoWrapFlags WrapType; | |||
| 1326 | // | |||
| 1327 | // static const ExtendOpTraitsBase::GetExtendExprTy GetExtendExpr; | |||
| 1328 | // | |||
| 1329 | // static const SCEV *getOverflowLimitForStep(const SCEV *Step, | |||
| 1330 | // ICmpInst::Predicate *Pred, | |||
| 1331 | // ScalarEvolution *SE); | |||
| 1332 | }; | |||
| 1333 | ||||
| 1334 | template <> | |||
| 1335 | struct ExtendOpTraits<SCEVSignExtendExpr> : public ExtendOpTraitsBase { | |||
| 1336 | static const SCEV::NoWrapFlags WrapType = SCEV::FlagNSW; | |||
| 1337 | ||||
| 1338 | static const GetExtendExprTy GetExtendExpr; | |||
| 1339 | ||||
| 1340 | static const SCEV *getOverflowLimitForStep(const SCEV *Step, | |||
| 1341 | ICmpInst::Predicate *Pred, | |||
| 1342 | ScalarEvolution *SE) { | |||
| 1343 | return getSignedOverflowLimitForStep(Step, Pred, SE); | |||
| 1344 | } | |||
| 1345 | }; | |||
| 1346 | ||||
| 1347 | const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits< | |||
| 1348 | SCEVSignExtendExpr>::GetExtendExpr = &ScalarEvolution::getSignExtendExpr; | |||
| 1349 | ||||
| 1350 | template <> | |||
| 1351 | struct ExtendOpTraits<SCEVZeroExtendExpr> : public ExtendOpTraitsBase { | |||
| 1352 | static const SCEV::NoWrapFlags WrapType = SCEV::FlagNUW; | |||
| 1353 | ||||
| 1354 | static const GetExtendExprTy GetExtendExpr; | |||
| 1355 | ||||
| 1356 | static const SCEV *getOverflowLimitForStep(const SCEV *Step, | |||
| 1357 | ICmpInst::Predicate *Pred, | |||
| 1358 | ScalarEvolution *SE) { | |||
| 1359 | return getUnsignedOverflowLimitForStep(Step, Pred, SE); | |||
| 1360 | } | |||
| 1361 | }; | |||
| 1362 | ||||
| 1363 | const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits< | |||
| 1364 | SCEVZeroExtendExpr>::GetExtendExpr = &ScalarEvolution::getZeroExtendExpr; | |||
| 1365 | ||||
| 1366 | } // end anonymous namespace | |||
| 1367 | ||||
| 1368 | // The recurrence AR has been shown to have no signed/unsigned wrap or something | |||
| 1369 | // close to it. Typically, if we can prove NSW/NUW for AR, then we can just as | |||
| 1370 | // easily prove NSW/NUW for its preincrement or postincrement sibling. This | |||
| 1371 | // allows normalizing a sign/zero extended AddRec as such: {sext/zext(Step + | |||
| 1372 | // Start),+,Step} => {(Step + sext/zext(Start),+,Step} As a result, the | |||
| 1373 | // expression "Step + sext/zext(PreIncAR)" is congruent with | |||
| 1374 | // "sext/zext(PostIncAR)" | |||
| 1375 | template <typename ExtendOpTy> | |||
| 1376 | static const SCEV *getPreStartForExtend(const SCEVAddRecExpr *AR, Type *Ty, | |||
| 1377 | ScalarEvolution *SE, unsigned Depth) { | |||
| 1378 | auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType; | |||
| 1379 | auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr; | |||
| 1380 | ||||
| 1381 | const Loop *L = AR->getLoop(); | |||
| 1382 | const SCEV *Start = AR->getStart(); | |||
| 1383 | const SCEV *Step = AR->getStepRecurrence(*SE); | |||
| 1384 | ||||
| 1385 | // Check for a simple looking step prior to loop entry. | |||
| 1386 | const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start); | |||
| 1387 | if (!SA) | |||
| 1388 | return nullptr; | |||
| 1389 | ||||
| 1390 | // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV | |||
| 1391 | // subtraction is expensive. For this purpose, perform a quick and dirty | |||
| 1392 | // difference, by checking for Step in the operand list. | |||
| 1393 | SmallVector<const SCEV *, 4> DiffOps; | |||
| 1394 | for (const SCEV *Op : SA->operands()) | |||
| 1395 | if (Op != Step) | |||
| 1396 | DiffOps.push_back(Op); | |||
| 1397 | ||||
| 1398 | if (DiffOps.size() == SA->getNumOperands()) | |||
| 1399 | return nullptr; | |||
| 1400 | ||||
| 1401 | // Try to prove `WrapType` (SCEV::FlagNSW or SCEV::FlagNUW) on `PreStart` + | |||
| 1402 | // `Step`: | |||
| 1403 | ||||
| 1404 | // 1. NSW/NUW flags on the step increment. | |||
| 1405 | auto PreStartFlags = | |||
| 1406 | ScalarEvolution::maskFlags(SA->getNoWrapFlags(), SCEV::FlagNUW); | |||
| 1407 | const SCEV *PreStart = SE->getAddExpr(DiffOps, PreStartFlags); | |||
| 1408 | const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>( | |||
| 1409 | SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap)); | |||
| 1410 | ||||
| 1411 | // "{S,+,X} is <nsw>/<nuw>" and "the backedge is taken at least once" implies | |||
| 1412 | // "S+X does not sign/unsign-overflow". | |||
| 1413 | // | |||
| 1414 | ||||
| 1415 | const SCEV *BECount = SE->getBackedgeTakenCount(L); | |||
| 1416 | if (PreAR && PreAR->getNoWrapFlags(WrapType) && | |||
| 1417 | !isa<SCEVCouldNotCompute>(BECount) && SE->isKnownPositive(BECount)) | |||
| 1418 | return PreStart; | |||
| 1419 | ||||
| 1420 | // 2. Direct overflow check on the step operation's expression. | |||
| 1421 | unsigned BitWidth = SE->getTypeSizeInBits(AR->getType()); | |||
| 1422 | Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2); | |||
| 1423 | const SCEV *OperandExtendedStart = | |||
| 1424 | SE->getAddExpr((SE->*GetExtendExpr)(PreStart, WideTy, Depth), | |||
| 1425 | (SE->*GetExtendExpr)(Step, WideTy, Depth)); | |||
| 1426 | if ((SE->*GetExtendExpr)(Start, WideTy, Depth) == OperandExtendedStart) { | |||
| 1427 | if (PreAR && AR->getNoWrapFlags(WrapType)) { | |||
| 1428 | // If we know `AR` == {`PreStart`+`Step`,+,`Step`} is `WrapType` (FlagNSW | |||
| 1429 | // or FlagNUW) and that `PreStart` + `Step` is `WrapType` too, then | |||
| 1430 | // `PreAR` == {`PreStart`,+,`Step`} is also `WrapType`. Cache this fact. | |||
| 1431 | SE->setNoWrapFlags(const_cast<SCEVAddRecExpr *>(PreAR), WrapType); | |||
| 1432 | } | |||
| 1433 | return PreStart; | |||
| 1434 | } | |||
| 1435 | ||||
| 1436 | // 3. Loop precondition. | |||
| 1437 | ICmpInst::Predicate Pred; | |||
| 1438 | const SCEV *OverflowLimit = | |||
| 1439 | ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(Step, &Pred, SE); | |||
| 1440 | ||||
| 1441 | if (OverflowLimit && | |||
| 1442 | SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) | |||
| 1443 | return PreStart; | |||
| 1444 | ||||
| 1445 | return nullptr; | |||
| 1446 | } | |||
| 1447 | ||||
| 1448 | // Get the normalized zero or sign extended expression for this AddRec's Start. | |||
| 1449 | template <typename ExtendOpTy> | |||
| 1450 | static const SCEV *getExtendAddRecStart(const SCEVAddRecExpr *AR, Type *Ty, | |||
| 1451 | ScalarEvolution *SE, | |||
| 1452 | unsigned Depth) { | |||
| 1453 | auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr; | |||
| 1454 | ||||
| 1455 | const SCEV *PreStart = getPreStartForExtend<ExtendOpTy>(AR, Ty, SE, Depth); | |||
| 1456 | if (!PreStart) | |||
| 1457 | return (SE->*GetExtendExpr)(AR->getStart(), Ty, Depth); | |||
| 1458 | ||||
| 1459 | return SE->getAddExpr((SE->*GetExtendExpr)(AR->getStepRecurrence(*SE), Ty, | |||
| 1460 | Depth), | |||
| 1461 | (SE->*GetExtendExpr)(PreStart, Ty, Depth)); | |||
| 1462 | } | |||
| 1463 | ||||
| 1464 | // Try to prove away overflow by looking at "nearby" add recurrences. A | |||
| 1465 | // motivating example for this rule: if we know `{0,+,4}` is `ult` `-1` and it | |||
| 1466 | // does not itself wrap then we can conclude that `{1,+,4}` is `nuw`. | |||
| 1467 | // | |||
| 1468 | // Formally: | |||
| 1469 | // | |||
| 1470 | // {S,+,X} == {S-T,+,X} + T | |||
| 1471 | // => Ext({S,+,X}) == Ext({S-T,+,X} + T) | |||
| 1472 | // | |||
| 1473 | // If ({S-T,+,X} + T) does not overflow ... (1) | |||
| 1474 | // | |||
| 1475 | // RHS == Ext({S-T,+,X} + T) == Ext({S-T,+,X}) + Ext(T) | |||
| 1476 | // | |||
| 1477 | // If {S-T,+,X} does not overflow ... (2) | |||
| 1478 | // | |||
| 1479 | // RHS == Ext({S-T,+,X}) + Ext(T) == {Ext(S-T),+,Ext(X)} + Ext(T) | |||
| 1480 | // == {Ext(S-T)+Ext(T),+,Ext(X)} | |||
| 1481 | // | |||
| 1482 | // If (S-T)+T does not overflow ... (3) | |||
| 1483 | // | |||
| 1484 | // RHS == {Ext(S-T)+Ext(T),+,Ext(X)} == {Ext(S-T+T),+,Ext(X)} | |||
| 1485 | // == {Ext(S),+,Ext(X)} == LHS | |||
| 1486 | // | |||
| 1487 | // Thus, if (1), (2) and (3) are true for some T, then | |||
| 1488 | // Ext({S,+,X}) == {Ext(S),+,Ext(X)} | |||
| 1489 | // | |||
| 1490 | // (3) is implied by (1) -- "(S-T)+T does not overflow" is simply "({S-T,+,X}+T) | |||
| 1491 | // does not overflow" restricted to the 0th iteration. Therefore we only need | |||
| 1492 | // to check for (1) and (2). | |||
| 1493 | // | |||
| 1494 | // In the current context, S is `Start`, X is `Step`, Ext is `ExtendOpTy` and T | |||
| 1495 | // is `Delta` (defined below). | |||
| 1496 | template <typename ExtendOpTy> | |||
| 1497 | bool ScalarEvolution::proveNoWrapByVaryingStart(const SCEV *Start, | |||
| 1498 | const SCEV *Step, | |||
| 1499 | const Loop *L) { | |||
| 1500 | auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType; | |||
| 1501 | ||||
| 1502 | // We restrict `Start` to a constant to prevent SCEV from spending too much | |||
| 1503 | // time here. It is correct (but more expensive) to continue with a | |||
| 1504 | // non-constant `Start` and do a general SCEV subtraction to compute | |||
| 1505 | // `PreStart` below. | |||
| 1506 | const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start); | |||
| 1507 | if (!StartC) | |||
| 1508 | return false; | |||
| 1509 | ||||
| 1510 | APInt StartAI = StartC->getAPInt(); | |||
| 1511 | ||||
| 1512 | for (unsigned Delta : {-2, -1, 1, 2}) { | |||
| 1513 | const SCEV *PreStart = getConstant(StartAI - Delta); | |||
| 1514 | ||||
| 1515 | FoldingSetNodeID ID; | |||
| 1516 | ID.AddInteger(scAddRecExpr); | |||
| 1517 | ID.AddPointer(PreStart); | |||
| 1518 | ID.AddPointer(Step); | |||
| 1519 | ID.AddPointer(L); | |||
| 1520 | void *IP = nullptr; | |||
| 1521 | const auto *PreAR = | |||
| 1522 | static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP)); | |||
| 1523 | ||||
| 1524 | // Give up if we don't already have the add recurrence we need because | |||
| 1525 | // actually constructing an add recurrence is relatively expensive. | |||
| 1526 | if (PreAR && PreAR->getNoWrapFlags(WrapType)) { // proves (2) | |||
| 1527 | const SCEV *DeltaS = getConstant(StartC->getType(), Delta); | |||
| 1528 | ICmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; | |||
| 1529 | const SCEV *Limit = ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep( | |||
| 1530 | DeltaS, &Pred, this); | |||
| 1531 | if (Limit && isKnownPredicate(Pred, PreAR, Limit)) // proves (1) | |||
| 1532 | return true; | |||
| 1533 | } | |||
| 1534 | } | |||
| 1535 | ||||
| 1536 | return false; | |||
| 1537 | } | |||
| 1538 | ||||
| 1539 | // Finds an integer D for an expression (C + x + y + ...) such that the top | |||
| 1540 | // level addition in (D + (C - D + x + y + ...)) would not wrap (signed or | |||
| 1541 | // unsigned) and the number of trailing zeros of (C - D + x + y + ...) is | |||
| 1542 | // maximized, where C is the \p ConstantTerm, x, y, ... are arbitrary SCEVs, and | |||
| 1543 | // the (C + x + y + ...) expression is \p WholeAddExpr. | |||
| 1544 | static APInt extractConstantWithoutWrapping(ScalarEvolution &SE, | |||
| 1545 | const SCEVConstant *ConstantTerm, | |||
| 1546 | const SCEVAddExpr *WholeAddExpr) { | |||
| 1547 | const APInt &C = ConstantTerm->getAPInt(); | |||
| 1548 | const unsigned BitWidth = C.getBitWidth(); | |||
| 1549 | // Find number of trailing zeros of (x + y + ...) w/o the C first: | |||
| 1550 | uint32_t TZ = BitWidth; | |||
| 1551 | for (unsigned I = 1, E = WholeAddExpr->getNumOperands(); I < E && TZ; ++I) | |||
| 1552 | TZ = std::min(TZ, SE.GetMinTrailingZeros(WholeAddExpr->getOperand(I))); | |||
| 1553 | if (TZ) { | |||
| 1554 | // Set D to be as many least significant bits of C as possible while still | |||
| 1555 | // guaranteeing that adding D to (C - D + x + y + ...) won't cause a wrap: | |||
| 1556 | return TZ < BitWidth ? C.trunc(TZ).zext(BitWidth) : C; | |||
| 1557 | } | |||
| 1558 | return APInt(BitWidth, 0); | |||
| 1559 | } | |||
| 1560 | ||||
| 1561 | // Finds an integer D for an affine AddRec expression {C,+,x} such that the top | |||
| 1562 | // level addition in (D + {C-D,+,x}) would not wrap (signed or unsigned) and the | |||
| 1563 | // number of trailing zeros of (C - D + x * n) is maximized, where C is the \p | |||
| 1564 | // ConstantStart, x is an arbitrary \p Step, and n is the loop trip count. | |||
| 1565 | static APInt extractConstantWithoutWrapping(ScalarEvolution &SE, | |||
| 1566 | const APInt &ConstantStart, | |||
| 1567 | const SCEV *Step) { | |||
| 1568 | const unsigned BitWidth = ConstantStart.getBitWidth(); | |||
| 1569 | const uint32_t TZ = SE.GetMinTrailingZeros(Step); | |||
| 1570 | if (TZ) | |||
| 1571 | return TZ < BitWidth ? ConstantStart.trunc(TZ).zext(BitWidth) | |||
| 1572 | : ConstantStart; | |||
| 1573 | return APInt(BitWidth, 0); | |||
| 1574 | } | |||
| 1575 | ||||
| 1576 | const SCEV * | |||
| 1577 | ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) { | |||
| 1578 | assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((void)0) | |||
| 1579 | "This is not an extending conversion!")((void)0); | |||
| 1580 | assert(isSCEVable(Ty) &&((void)0) | |||
| 1581 | "This is not a conversion to a SCEVable type!")((void)0); | |||
| 1582 | assert(!Op->getType()->isPointerTy() && "Can't extend pointer!")((void)0); | |||
| 1583 | Ty = getEffectiveSCEVType(Ty); | |||
| 1584 | ||||
| 1585 | // Fold if the operand is constant. | |||
| 1586 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) | |||
| 1587 | return getConstant( | |||
| 1588 | cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty))); | |||
| 1589 | ||||
| 1590 | // zext(zext(x)) --> zext(x) | |||
| 1591 | if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op)) | |||
| 1592 | return getZeroExtendExpr(SZ->getOperand(), Ty, Depth + 1); | |||
| 1593 | ||||
| 1594 | // Before doing any expensive analysis, check to see if we've already | |||
| 1595 | // computed a SCEV for this Op and Ty. | |||
| 1596 | FoldingSetNodeID ID; | |||
| 1597 | ID.AddInteger(scZeroExtend); | |||
| 1598 | ID.AddPointer(Op); | |||
| 1599 | ID.AddPointer(Ty); | |||
| 1600 | void *IP = nullptr; | |||
| 1601 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 1602 | if (Depth > MaxCastDepth) { | |||
| 1603 | SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator), | |||
| 1604 | Op, Ty); | |||
| 1605 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1606 | addToLoopUseLists(S); | |||
| 1607 | return S; | |||
| 1608 | } | |||
| 1609 | ||||
| 1610 | // zext(trunc(x)) --> zext(x) or x or trunc(x) | |||
| 1611 | if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) { | |||
| 1612 | // It's possible the bits taken off by the truncate were all zero bits. If | |||
| 1613 | // so, we should be able to simplify this further. | |||
| 1614 | const SCEV *X = ST->getOperand(); | |||
| 1615 | ConstantRange CR = getUnsignedRange(X); | |||
| 1616 | unsigned TruncBits = getTypeSizeInBits(ST->getType()); | |||
| 1617 | unsigned NewBits = getTypeSizeInBits(Ty); | |||
| 1618 | if (CR.truncate(TruncBits).zeroExtend(NewBits).contains( | |||
| 1619 | CR.zextOrTrunc(NewBits))) | |||
| 1620 | return getTruncateOrZeroExtend(X, Ty, Depth); | |||
| 1621 | } | |||
| 1622 | ||||
| 1623 | // If the input value is a chrec scev, and we can prove that the value | |||
| 1624 | // did not overflow the old, smaller, value, we can zero extend all of the | |||
| 1625 | // operands (often constants). This allows analysis of something like | |||
| 1626 | // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; } | |||
| 1627 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) | |||
| 1628 | if (AR->isAffine()) { | |||
| 1629 | const SCEV *Start = AR->getStart(); | |||
| 1630 | const SCEV *Step = AR->getStepRecurrence(*this); | |||
| 1631 | unsigned BitWidth = getTypeSizeInBits(AR->getType()); | |||
| 1632 | const Loop *L = AR->getLoop(); | |||
| 1633 | ||||
| 1634 | if (!AR->hasNoUnsignedWrap()) { | |||
| 1635 | auto NewFlags = proveNoWrapViaConstantRanges(AR); | |||
| 1636 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), NewFlags); | |||
| 1637 | } | |||
| 1638 | ||||
| 1639 | // If we have special knowledge that this addrec won't overflow, | |||
| 1640 | // we don't need to do any further analysis. | |||
| 1641 | if (AR->hasNoUnsignedWrap()) | |||
| 1642 | return getAddRecExpr( | |||
| 1643 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Depth + 1), | |||
| 1644 | getZeroExtendExpr(Step, Ty, Depth + 1), L, AR->getNoWrapFlags()); | |||
| 1645 | ||||
| 1646 | // Check whether the backedge-taken count is SCEVCouldNotCompute. | |||
| 1647 | // Note that this serves two purposes: It filters out loops that are | |||
| 1648 | // simply not analyzable, and it covers the case where this code is | |||
| 1649 | // being called from within backedge-taken count analysis, such that | |||
| 1650 | // attempting to ask for the backedge-taken count would likely result | |||
| 1651 | // in infinite recursion. In the later case, the analysis code will | |||
| 1652 | // cope with a conservative value, and it will take care to purge | |||
| 1653 | // that value once it has finished. | |||
| 1654 | const SCEV *MaxBECount = getConstantMaxBackedgeTakenCount(L); | |||
| 1655 | if (!isa<SCEVCouldNotCompute>(MaxBECount)) { | |||
| 1656 | // Manually compute the final value for AR, checking for overflow. | |||
| 1657 | ||||
| 1658 | // Check whether the backedge-taken count can be losslessly casted to | |||
| 1659 | // the addrec's type. The count is always unsigned. | |||
| 1660 | const SCEV *CastedMaxBECount = | |||
| 1661 | getTruncateOrZeroExtend(MaxBECount, Start->getType(), Depth); | |||
| 1662 | const SCEV *RecastedMaxBECount = getTruncateOrZeroExtend( | |||
| 1663 | CastedMaxBECount, MaxBECount->getType(), Depth); | |||
| 1664 | if (MaxBECount == RecastedMaxBECount) { | |||
| 1665 | Type *WideTy = IntegerType::get(getContext(), BitWidth * 2); | |||
| 1666 | // Check whether Start+Step*MaxBECount has no unsigned overflow. | |||
| 1667 | const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step, | |||
| 1668 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 1669 | const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul, | |||
| 1670 | SCEV::FlagAnyWrap, | |||
| 1671 | Depth + 1), | |||
| 1672 | WideTy, Depth + 1); | |||
| 1673 | const SCEV *WideStart = getZeroExtendExpr(Start, WideTy, Depth + 1); | |||
| 1674 | const SCEV *WideMaxBECount = | |||
| 1675 | getZeroExtendExpr(CastedMaxBECount, WideTy, Depth + 1); | |||
| 1676 | const SCEV *OperandExtendedAdd = | |||
| 1677 | getAddExpr(WideStart, | |||
| 1678 | getMulExpr(WideMaxBECount, | |||
| 1679 | getZeroExtendExpr(Step, WideTy, Depth + 1), | |||
| 1680 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 1681 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 1682 | if (ZAdd == OperandExtendedAdd) { | |||
| 1683 | // Cache knowledge of AR NUW, which is propagated to this AddRec. | |||
| 1684 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNUW); | |||
| 1685 | // Return the expression with the addrec on the outside. | |||
| 1686 | return getAddRecExpr( | |||
| 1687 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, | |||
| 1688 | Depth + 1), | |||
| 1689 | getZeroExtendExpr(Step, Ty, Depth + 1), L, | |||
| 1690 | AR->getNoWrapFlags()); | |||
| 1691 | } | |||
| 1692 | // Similar to above, only this time treat the step value as signed. | |||
| 1693 | // This covers loops that count down. | |||
| 1694 | OperandExtendedAdd = | |||
| 1695 | getAddExpr(WideStart, | |||
| 1696 | getMulExpr(WideMaxBECount, | |||
| 1697 | getSignExtendExpr(Step, WideTy, Depth + 1), | |||
| 1698 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 1699 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 1700 | if (ZAdd == OperandExtendedAdd) { | |||
| 1701 | // Cache knowledge of AR NW, which is propagated to this AddRec. | |||
| 1702 | // Negative step causes unsigned wrap, but it still can't self-wrap. | |||
| 1703 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNW); | |||
| 1704 | // Return the expression with the addrec on the outside. | |||
| 1705 | return getAddRecExpr( | |||
| 1706 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, | |||
| 1707 | Depth + 1), | |||
| 1708 | getSignExtendExpr(Step, Ty, Depth + 1), L, | |||
| 1709 | AR->getNoWrapFlags()); | |||
| 1710 | } | |||
| 1711 | } | |||
| 1712 | } | |||
| 1713 | ||||
| 1714 | // Normally, in the cases we can prove no-overflow via a | |||
| 1715 | // backedge guarding condition, we can also compute a backedge | |||
| 1716 | // taken count for the loop. The exceptions are assumptions and | |||
| 1717 | // guards present in the loop -- SCEV is not great at exploiting | |||
| 1718 | // these to compute max backedge taken counts, but can still use | |||
| 1719 | // these to prove lack of overflow. Use this fact to avoid | |||
| 1720 | // doing extra work that may not pay off. | |||
| 1721 | if (!isa<SCEVCouldNotCompute>(MaxBECount) || HasGuards || | |||
| 1722 | !AC.assumptions().empty()) { | |||
| 1723 | ||||
| 1724 | auto NewFlags = proveNoUnsignedWrapViaInduction(AR); | |||
| 1725 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), NewFlags); | |||
| 1726 | if (AR->hasNoUnsignedWrap()) { | |||
| 1727 | // Same as nuw case above - duplicated here to avoid a compile time | |||
| 1728 | // issue. It's not clear that the order of checks does matter, but | |||
| 1729 | // it's one of two issue possible causes for a change which was | |||
| 1730 | // reverted. Be conservative for the moment. | |||
| 1731 | return getAddRecExpr( | |||
| 1732 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, | |||
| 1733 | Depth + 1), | |||
| 1734 | getZeroExtendExpr(Step, Ty, Depth + 1), L, | |||
| 1735 | AR->getNoWrapFlags()); | |||
| 1736 | } | |||
| 1737 | ||||
| 1738 | // For a negative step, we can extend the operands iff doing so only | |||
| 1739 | // traverses values in the range zext([0,UINT_MAX]). | |||
| 1740 | if (isKnownNegative(Step)) { | |||
| 1741 | const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) - | |||
| 1742 | getSignedRangeMin(Step)); | |||
| 1743 | if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) || | |||
| 1744 | isKnownOnEveryIteration(ICmpInst::ICMP_UGT, AR, N)) { | |||
| 1745 | // Cache knowledge of AR NW, which is propagated to this | |||
| 1746 | // AddRec. Negative step causes unsigned wrap, but it | |||
| 1747 | // still can't self-wrap. | |||
| 1748 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNW); | |||
| 1749 | // Return the expression with the addrec on the outside. | |||
| 1750 | return getAddRecExpr( | |||
| 1751 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, | |||
| 1752 | Depth + 1), | |||
| 1753 | getSignExtendExpr(Step, Ty, Depth + 1), L, | |||
| 1754 | AR->getNoWrapFlags()); | |||
| 1755 | } | |||
| 1756 | } | |||
| 1757 | } | |||
| 1758 | ||||
| 1759 | // zext({C,+,Step}) --> (zext(D) + zext({C-D,+,Step}))<nuw><nsw> | |||
| 1760 | // if D + (C - D + Step * n) could be proven to not unsigned wrap | |||
| 1761 | // where D maximizes the number of trailing zeros of (C - D + Step * n) | |||
| 1762 | if (const auto *SC = dyn_cast<SCEVConstant>(Start)) { | |||
| 1763 | const APInt &C = SC->getAPInt(); | |||
| 1764 | const APInt &D = extractConstantWithoutWrapping(*this, C, Step); | |||
| 1765 | if (D != 0) { | |||
| 1766 | const SCEV *SZExtD = getZeroExtendExpr(getConstant(D), Ty, Depth); | |||
| 1767 | const SCEV *SResidual = | |||
| 1768 | getAddRecExpr(getConstant(C - D), Step, L, AR->getNoWrapFlags()); | |||
| 1769 | const SCEV *SZExtR = getZeroExtendExpr(SResidual, Ty, Depth + 1); | |||
| 1770 | return getAddExpr(SZExtD, SZExtR, | |||
| 1771 | (SCEV::NoWrapFlags)(SCEV::FlagNSW | SCEV::FlagNUW), | |||
| 1772 | Depth + 1); | |||
| 1773 | } | |||
| 1774 | } | |||
| 1775 | ||||
| 1776 | if (proveNoWrapByVaryingStart<SCEVZeroExtendExpr>(Start, Step, L)) { | |||
| 1777 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNUW); | |||
| 1778 | return getAddRecExpr( | |||
| 1779 | getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this, Depth + 1), | |||
| 1780 | getZeroExtendExpr(Step, Ty, Depth + 1), L, AR->getNoWrapFlags()); | |||
| 1781 | } | |||
| 1782 | } | |||
| 1783 | ||||
| 1784 | // zext(A % B) --> zext(A) % zext(B) | |||
| 1785 | { | |||
| 1786 | const SCEV *LHS; | |||
| 1787 | const SCEV *RHS; | |||
| 1788 | if (matchURem(Op, LHS, RHS)) | |||
| 1789 | return getURemExpr(getZeroExtendExpr(LHS, Ty, Depth + 1), | |||
| 1790 | getZeroExtendExpr(RHS, Ty, Depth + 1)); | |||
| 1791 | } | |||
| 1792 | ||||
| 1793 | // zext(A / B) --> zext(A) / zext(B). | |||
| 1794 | if (auto *Div = dyn_cast<SCEVUDivExpr>(Op)) | |||
| 1795 | return getUDivExpr(getZeroExtendExpr(Div->getLHS(), Ty, Depth + 1), | |||
| 1796 | getZeroExtendExpr(Div->getRHS(), Ty, Depth + 1)); | |||
| 1797 | ||||
| 1798 | if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) { | |||
| 1799 | // zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw> | |||
| 1800 | if (SA->hasNoUnsignedWrap()) { | |||
| 1801 | // If the addition does not unsign overflow then we can, by definition, | |||
| 1802 | // commute the zero extension with the addition operation. | |||
| 1803 | SmallVector<const SCEV *, 4> Ops; | |||
| 1804 | for (const auto *Op : SA->operands()) | |||
| 1805 | Ops.push_back(getZeroExtendExpr(Op, Ty, Depth + 1)); | |||
| 1806 | return getAddExpr(Ops, SCEV::FlagNUW, Depth + 1); | |||
| 1807 | } | |||
| 1808 | ||||
| 1809 | // zext(C + x + y + ...) --> (zext(D) + zext((C - D) + x + y + ...)) | |||
| 1810 | // if D + (C - D + x + y + ...) could be proven to not unsigned wrap | |||
| 1811 | // where D maximizes the number of trailing zeros of (C - D + x + y + ...) | |||
| 1812 | // | |||
| 1813 | // Often address arithmetics contain expressions like | |||
| 1814 | // (zext (add (shl X, C1), C2)), for instance, (zext (5 + (4 * X))). | |||
| 1815 | // This transformation is useful while proving that such expressions are | |||
| 1816 | // equal or differ by a small constant amount, see LoadStoreVectorizer pass. | |||
| 1817 | if (const auto *SC = dyn_cast<SCEVConstant>(SA->getOperand(0))) { | |||
| 1818 | const APInt &D = extractConstantWithoutWrapping(*this, SC, SA); | |||
| 1819 | if (D != 0) { | |||
| 1820 | const SCEV *SZExtD = getZeroExtendExpr(getConstant(D), Ty, Depth); | |||
| 1821 | const SCEV *SResidual = | |||
| 1822 | getAddExpr(getConstant(-D), SA, SCEV::FlagAnyWrap, Depth); | |||
| 1823 | const SCEV *SZExtR = getZeroExtendExpr(SResidual, Ty, Depth + 1); | |||
| 1824 | return getAddExpr(SZExtD, SZExtR, | |||
| 1825 | (SCEV::NoWrapFlags)(SCEV::FlagNSW | SCEV::FlagNUW), | |||
| 1826 | Depth + 1); | |||
| 1827 | } | |||
| 1828 | } | |||
| 1829 | } | |||
| 1830 | ||||
| 1831 | if (auto *SM = dyn_cast<SCEVMulExpr>(Op)) { | |||
| 1832 | // zext((A * B * ...)<nuw>) --> (zext(A) * zext(B) * ...)<nuw> | |||
| 1833 | if (SM->hasNoUnsignedWrap()) { | |||
| 1834 | // If the multiply does not unsign overflow then we can, by definition, | |||
| 1835 | // commute the zero extension with the multiply operation. | |||
| 1836 | SmallVector<const SCEV *, 4> Ops; | |||
| 1837 | for (const auto *Op : SM->operands()) | |||
| 1838 | Ops.push_back(getZeroExtendExpr(Op, Ty, Depth + 1)); | |||
| 1839 | return getMulExpr(Ops, SCEV::FlagNUW, Depth + 1); | |||
| 1840 | } | |||
| 1841 | ||||
| 1842 | // zext(2^K * (trunc X to iN)) to iM -> | |||
| 1843 | // 2^K * (zext(trunc X to i{N-K}) to iM)<nuw> | |||
| 1844 | // | |||
| 1845 | // Proof: | |||
| 1846 | // | |||
| 1847 | // zext(2^K * (trunc X to iN)) to iM | |||
| 1848 | // = zext((trunc X to iN) << K) to iM | |||
| 1849 | // = zext((trunc X to i{N-K}) << K)<nuw> to iM | |||
| 1850 | // (because shl removes the top K bits) | |||
| 1851 | // = zext((2^K * (trunc X to i{N-K}))<nuw>) to iM | |||
| 1852 | // = (2^K * (zext(trunc X to i{N-K}) to iM))<nuw>. | |||
| 1853 | // | |||
| 1854 | if (SM->getNumOperands() == 2) | |||
| 1855 | if (auto *MulLHS = dyn_cast<SCEVConstant>(SM->getOperand(0))) | |||
| 1856 | if (MulLHS->getAPInt().isPowerOf2()) | |||
| 1857 | if (auto *TruncRHS = dyn_cast<SCEVTruncateExpr>(SM->getOperand(1))) { | |||
| 1858 | int NewTruncBits = getTypeSizeInBits(TruncRHS->getType()) - | |||
| 1859 | MulLHS->getAPInt().logBase2(); | |||
| 1860 | Type *NewTruncTy = IntegerType::get(getContext(), NewTruncBits); | |||
| 1861 | return getMulExpr( | |||
| 1862 | getZeroExtendExpr(MulLHS, Ty), | |||
| 1863 | getZeroExtendExpr( | |||
| 1864 | getTruncateExpr(TruncRHS->getOperand(), NewTruncTy), Ty), | |||
| 1865 | SCEV::FlagNUW, Depth + 1); | |||
| 1866 | } | |||
| 1867 | } | |||
| 1868 | ||||
| 1869 | // The cast wasn't folded; create an explicit cast node. | |||
| 1870 | // Recompute the insert position, as it may have been invalidated. | |||
| 1871 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 1872 | SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator), | |||
| 1873 | Op, Ty); | |||
| 1874 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1875 | addToLoopUseLists(S); | |||
| 1876 | return S; | |||
| 1877 | } | |||
| 1878 | ||||
| 1879 | const SCEV * | |||
| 1880 | ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) { | |||
| 1881 | assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((void)0) | |||
| 1882 | "This is not an extending conversion!")((void)0); | |||
| 1883 | assert(isSCEVable(Ty) &&((void)0) | |||
| 1884 | "This is not a conversion to a SCEVable type!")((void)0); | |||
| 1885 | assert(!Op->getType()->isPointerTy() && "Can't extend pointer!")((void)0); | |||
| 1886 | Ty = getEffectiveSCEVType(Ty); | |||
| 1887 | ||||
| 1888 | // Fold if the operand is constant. | |||
| 1889 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) | |||
| 1890 | return getConstant( | |||
| 1891 | cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty))); | |||
| 1892 | ||||
| 1893 | // sext(sext(x)) --> sext(x) | |||
| 1894 | if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op)) | |||
| 1895 | return getSignExtendExpr(SS->getOperand(), Ty, Depth + 1); | |||
| 1896 | ||||
| 1897 | // sext(zext(x)) --> zext(x) | |||
| 1898 | if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op)) | |||
| 1899 | return getZeroExtendExpr(SZ->getOperand(), Ty, Depth + 1); | |||
| 1900 | ||||
| 1901 | // Before doing any expensive analysis, check to see if we've already | |||
| 1902 | // computed a SCEV for this Op and Ty. | |||
| 1903 | FoldingSetNodeID ID; | |||
| 1904 | ID.AddInteger(scSignExtend); | |||
| 1905 | ID.AddPointer(Op); | |||
| 1906 | ID.AddPointer(Ty); | |||
| 1907 | void *IP = nullptr; | |||
| 1908 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 1909 | // Limit recursion depth. | |||
| 1910 | if (Depth > MaxCastDepth) { | |||
| 1911 | SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator), | |||
| 1912 | Op, Ty); | |||
| 1913 | UniqueSCEVs.InsertNode(S, IP); | |||
| 1914 | addToLoopUseLists(S); | |||
| 1915 | return S; | |||
| 1916 | } | |||
| 1917 | ||||
| 1918 | // sext(trunc(x)) --> sext(x) or x or trunc(x) | |||
| 1919 | if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) { | |||
| 1920 | // It's possible the bits taken off by the truncate were all sign bits. If | |||
| 1921 | // so, we should be able to simplify this further. | |||
| 1922 | const SCEV *X = ST->getOperand(); | |||
| 1923 | ConstantRange CR = getSignedRange(X); | |||
| 1924 | unsigned TruncBits = getTypeSizeInBits(ST->getType()); | |||
| 1925 | unsigned NewBits = getTypeSizeInBits(Ty); | |||
| 1926 | if (CR.truncate(TruncBits).signExtend(NewBits).contains( | |||
| 1927 | CR.sextOrTrunc(NewBits))) | |||
| 1928 | return getTruncateOrSignExtend(X, Ty, Depth); | |||
| 1929 | } | |||
| 1930 | ||||
| 1931 | if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) { | |||
| 1932 | // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw> | |||
| 1933 | if (SA->hasNoSignedWrap()) { | |||
| 1934 | // If the addition does not sign overflow then we can, by definition, | |||
| 1935 | // commute the sign extension with the addition operation. | |||
| 1936 | SmallVector<const SCEV *, 4> Ops; | |||
| 1937 | for (const auto *Op : SA->operands()) | |||
| 1938 | Ops.push_back(getSignExtendExpr(Op, Ty, Depth + 1)); | |||
| 1939 | return getAddExpr(Ops, SCEV::FlagNSW, Depth + 1); | |||
| 1940 | } | |||
| 1941 | ||||
| 1942 | // sext(C + x + y + ...) --> (sext(D) + sext((C - D) + x + y + ...)) | |||
| 1943 | // if D + (C - D + x + y + ...) could be proven to not signed wrap | |||
| 1944 | // where D maximizes the number of trailing zeros of (C - D + x + y + ...) | |||
| 1945 | // | |||
| 1946 | // For instance, this will bring two seemingly different expressions: | |||
| 1947 | // 1 + sext(5 + 20 * %x + 24 * %y) and | |||
| 1948 | // sext(6 + 20 * %x + 24 * %y) | |||
| 1949 | // to the same form: | |||
| 1950 | // 2 + sext(4 + 20 * %x + 24 * %y) | |||
| 1951 | if (const auto *SC = dyn_cast<SCEVConstant>(SA->getOperand(0))) { | |||
| 1952 | const APInt &D = extractConstantWithoutWrapping(*this, SC, SA); | |||
| 1953 | if (D != 0) { | |||
| 1954 | const SCEV *SSExtD = getSignExtendExpr(getConstant(D), Ty, Depth); | |||
| 1955 | const SCEV *SResidual = | |||
| 1956 | getAddExpr(getConstant(-D), SA, SCEV::FlagAnyWrap, Depth); | |||
| 1957 | const SCEV *SSExtR = getSignExtendExpr(SResidual, Ty, Depth + 1); | |||
| 1958 | return getAddExpr(SSExtD, SSExtR, | |||
| 1959 | (SCEV::NoWrapFlags)(SCEV::FlagNSW | SCEV::FlagNUW), | |||
| 1960 | Depth + 1); | |||
| 1961 | } | |||
| 1962 | } | |||
| 1963 | } | |||
| 1964 | // If the input value is a chrec scev, and we can prove that the value | |||
| 1965 | // did not overflow the old, smaller, value, we can sign extend all of the | |||
| 1966 | // operands (often constants). This allows analysis of something like | |||
| 1967 | // this: for (signed char X = 0; X < 100; ++X) { int Y = X; } | |||
| 1968 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) | |||
| 1969 | if (AR->isAffine()) { | |||
| 1970 | const SCEV *Start = AR->getStart(); | |||
| 1971 | const SCEV *Step = AR->getStepRecurrence(*this); | |||
| 1972 | unsigned BitWidth = getTypeSizeInBits(AR->getType()); | |||
| 1973 | const Loop *L = AR->getLoop(); | |||
| 1974 | ||||
| 1975 | if (!AR->hasNoSignedWrap()) { | |||
| 1976 | auto NewFlags = proveNoWrapViaConstantRanges(AR); | |||
| 1977 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), NewFlags); | |||
| 1978 | } | |||
| 1979 | ||||
| 1980 | // If we have special knowledge that this addrec won't overflow, | |||
| 1981 | // we don't need to do any further analysis. | |||
| 1982 | if (AR->hasNoSignedWrap()) | |||
| 1983 | return getAddRecExpr( | |||
| 1984 | getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Depth + 1), | |||
| 1985 | getSignExtendExpr(Step, Ty, Depth + 1), L, SCEV::FlagNSW); | |||
| 1986 | ||||
| 1987 | // Check whether the backedge-taken count is SCEVCouldNotCompute. | |||
| 1988 | // Note that this serves two purposes: It filters out loops that are | |||
| 1989 | // simply not analyzable, and it covers the case where this code is | |||
| 1990 | // being called from within backedge-taken count analysis, such that | |||
| 1991 | // attempting to ask for the backedge-taken count would likely result | |||
| 1992 | // in infinite recursion. In the later case, the analysis code will | |||
| 1993 | // cope with a conservative value, and it will take care to purge | |||
| 1994 | // that value once it has finished. | |||
| 1995 | const SCEV *MaxBECount = getConstantMaxBackedgeTakenCount(L); | |||
| 1996 | if (!isa<SCEVCouldNotCompute>(MaxBECount)) { | |||
| 1997 | // Manually compute the final value for AR, checking for | |||
| 1998 | // overflow. | |||
| 1999 | ||||
| 2000 | // Check whether the backedge-taken count can be losslessly casted to | |||
| 2001 | // the addrec's type. The count is always unsigned. | |||
| 2002 | const SCEV *CastedMaxBECount = | |||
| 2003 | getTruncateOrZeroExtend(MaxBECount, Start->getType(), Depth); | |||
| 2004 | const SCEV *RecastedMaxBECount = getTruncateOrZeroExtend( | |||
| 2005 | CastedMaxBECount, MaxBECount->getType(), Depth); | |||
| 2006 | if (MaxBECount == RecastedMaxBECount) { | |||
| 2007 | Type *WideTy = IntegerType::get(getContext(), BitWidth * 2); | |||
| 2008 | // Check whether Start+Step*MaxBECount has no signed overflow. | |||
| 2009 | const SCEV *SMul = getMulExpr(CastedMaxBECount, Step, | |||
| 2010 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 2011 | const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul, | |||
| 2012 | SCEV::FlagAnyWrap, | |||
| 2013 | Depth + 1), | |||
| 2014 | WideTy, Depth + 1); | |||
| 2015 | const SCEV *WideStart = getSignExtendExpr(Start, WideTy, Depth + 1); | |||
| 2016 | const SCEV *WideMaxBECount = | |||
| 2017 | getZeroExtendExpr(CastedMaxBECount, WideTy, Depth + 1); | |||
| 2018 | const SCEV *OperandExtendedAdd = | |||
| 2019 | getAddExpr(WideStart, | |||
| 2020 | getMulExpr(WideMaxBECount, | |||
| 2021 | getSignExtendExpr(Step, WideTy, Depth + 1), | |||
| 2022 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 2023 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 2024 | if (SAdd == OperandExtendedAdd) { | |||
| 2025 | // Cache knowledge of AR NSW, which is propagated to this AddRec. | |||
| 2026 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNSW); | |||
| 2027 | // Return the expression with the addrec on the outside. | |||
| 2028 | return getAddRecExpr( | |||
| 2029 | getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, | |||
| 2030 | Depth + 1), | |||
| 2031 | getSignExtendExpr(Step, Ty, Depth + 1), L, | |||
| 2032 | AR->getNoWrapFlags()); | |||
| 2033 | } | |||
| 2034 | // Similar to above, only this time treat the step value as unsigned. | |||
| 2035 | // This covers loops that count up with an unsigned step. | |||
| 2036 | OperandExtendedAdd = | |||
| 2037 | getAddExpr(WideStart, | |||
| 2038 | getMulExpr(WideMaxBECount, | |||
| 2039 | getZeroExtendExpr(Step, WideTy, Depth + 1), | |||
| 2040 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 2041 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 2042 | if (SAdd == OperandExtendedAdd) { | |||
| 2043 | // If AR wraps around then | |||
| 2044 | // | |||
| 2045 | // abs(Step) * MaxBECount > unsigned-max(AR->getType()) | |||
| 2046 | // => SAdd != OperandExtendedAdd | |||
| 2047 | // | |||
| 2048 | // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=> | |||
| 2049 | // (SAdd == OperandExtendedAdd => AR is NW) | |||
| 2050 | ||||
| 2051 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNW); | |||
| 2052 | ||||
| 2053 | // Return the expression with the addrec on the outside. | |||
| 2054 | return getAddRecExpr( | |||
| 2055 | getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, | |||
| 2056 | Depth + 1), | |||
| 2057 | getZeroExtendExpr(Step, Ty, Depth + 1), L, | |||
| 2058 | AR->getNoWrapFlags()); | |||
| 2059 | } | |||
| 2060 | } | |||
| 2061 | } | |||
| 2062 | ||||
| 2063 | auto NewFlags = proveNoSignedWrapViaInduction(AR); | |||
| 2064 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), NewFlags); | |||
| 2065 | if (AR->hasNoSignedWrap()) { | |||
| 2066 | // Same as nsw case above - duplicated here to avoid a compile time | |||
| 2067 | // issue. It's not clear that the order of checks does matter, but | |||
| 2068 | // it's one of two issue possible causes for a change which was | |||
| 2069 | // reverted. Be conservative for the moment. | |||
| 2070 | return getAddRecExpr( | |||
| 2071 | getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Depth + 1), | |||
| 2072 | getSignExtendExpr(Step, Ty, Depth + 1), L, AR->getNoWrapFlags()); | |||
| 2073 | } | |||
| 2074 | ||||
| 2075 | // sext({C,+,Step}) --> (sext(D) + sext({C-D,+,Step}))<nuw><nsw> | |||
| 2076 | // if D + (C - D + Step * n) could be proven to not signed wrap | |||
| 2077 | // where D maximizes the number of trailing zeros of (C - D + Step * n) | |||
| 2078 | if (const auto *SC = dyn_cast<SCEVConstant>(Start)) { | |||
| 2079 | const APInt &C = SC->getAPInt(); | |||
| 2080 | const APInt &D = extractConstantWithoutWrapping(*this, C, Step); | |||
| 2081 | if (D != 0) { | |||
| 2082 | const SCEV *SSExtD = getSignExtendExpr(getConstant(D), Ty, Depth); | |||
| 2083 | const SCEV *SResidual = | |||
| 2084 | getAddRecExpr(getConstant(C - D), Step, L, AR->getNoWrapFlags()); | |||
| 2085 | const SCEV *SSExtR = getSignExtendExpr(SResidual, Ty, Depth + 1); | |||
| 2086 | return getAddExpr(SSExtD, SSExtR, | |||
| 2087 | (SCEV::NoWrapFlags)(SCEV::FlagNSW | SCEV::FlagNUW), | |||
| 2088 | Depth + 1); | |||
| 2089 | } | |||
| 2090 | } | |||
| 2091 | ||||
| 2092 | if (proveNoWrapByVaryingStart<SCEVSignExtendExpr>(Start, Step, L)) { | |||
| 2093 | setNoWrapFlags(const_cast<SCEVAddRecExpr *>(AR), SCEV::FlagNSW); | |||
| 2094 | return getAddRecExpr( | |||
| 2095 | getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this, Depth + 1), | |||
| 2096 | getSignExtendExpr(Step, Ty, Depth + 1), L, AR->getNoWrapFlags()); | |||
| 2097 | } | |||
| 2098 | } | |||
| 2099 | ||||
| 2100 | // If the input value is provably positive and we could not simplify | |||
| 2101 | // away the sext build a zext instead. | |||
| 2102 | if (isKnownNonNegative(Op)) | |||
| 2103 | return getZeroExtendExpr(Op, Ty, Depth + 1); | |||
| 2104 | ||||
| 2105 | // The cast wasn't folded; create an explicit cast node. | |||
| 2106 | // Recompute the insert position, as it may have been invalidated. | |||
| 2107 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 2108 | SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator), | |||
| 2109 | Op, Ty); | |||
| 2110 | UniqueSCEVs.InsertNode(S, IP); | |||
| 2111 | addToLoopUseLists(S); | |||
| 2112 | return S; | |||
| 2113 | } | |||
| 2114 | ||||
| 2115 | /// getAnyExtendExpr - Return a SCEV for the given operand extended with | |||
| 2116 | /// unspecified bits out to the given type. | |||
| 2117 | const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op, | |||
| 2118 | Type *Ty) { | |||
| 2119 | assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((void)0) | |||
| 2120 | "This is not an extending conversion!")((void)0); | |||
| 2121 | assert(isSCEVable(Ty) &&((void)0) | |||
| 2122 | "This is not a conversion to a SCEVable type!")((void)0); | |||
| 2123 | Ty = getEffectiveSCEVType(Ty); | |||
| 2124 | ||||
| 2125 | // Sign-extend negative constants. | |||
| 2126 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) | |||
| 2127 | if (SC->getAPInt().isNegative()) | |||
| 2128 | return getSignExtendExpr(Op, Ty); | |||
| 2129 | ||||
| 2130 | // Peel off a truncate cast. | |||
| 2131 | if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) { | |||
| 2132 | const SCEV *NewOp = T->getOperand(); | |||
| 2133 | if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty)) | |||
| 2134 | return getAnyExtendExpr(NewOp, Ty); | |||
| 2135 | return getTruncateOrNoop(NewOp, Ty); | |||
| 2136 | } | |||
| 2137 | ||||
| 2138 | // Next try a zext cast. If the cast is folded, use it. | |||
| 2139 | const SCEV *ZExt = getZeroExtendExpr(Op, Ty); | |||
| 2140 | if (!isa<SCEVZeroExtendExpr>(ZExt)) | |||
| 2141 | return ZExt; | |||
| 2142 | ||||
| 2143 | // Next try a sext cast. If the cast is folded, use it. | |||
| 2144 | const SCEV *SExt = getSignExtendExpr(Op, Ty); | |||
| 2145 | if (!isa<SCEVSignExtendExpr>(SExt)) | |||
| 2146 | return SExt; | |||
| 2147 | ||||
| 2148 | // Force the cast to be folded into the operands of an addrec. | |||
| 2149 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) { | |||
| 2150 | SmallVector<const SCEV *, 4> Ops; | |||
| 2151 | for (const SCEV *Op : AR->operands()) | |||
| 2152 | Ops.push_back(getAnyExtendExpr(Op, Ty)); | |||
| 2153 | return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW); | |||
| 2154 | } | |||
| 2155 | ||||
| 2156 | // If the expression is obviously signed, use the sext cast value. | |||
| 2157 | if (isa<SCEVSMaxExpr>(Op)) | |||
| 2158 | return SExt; | |||
| 2159 | ||||
| 2160 | // Absent any other information, use the zext cast value. | |||
| 2161 | return ZExt; | |||
| 2162 | } | |||
| 2163 | ||||
| 2164 | /// Process the given Ops list, which is a list of operands to be added under | |||
| 2165 | /// the given scale, update the given map. This is a helper function for | |||
| 2166 | /// getAddRecExpr. As an example of what it does, given a sequence of operands | |||
| 2167 | /// that would form an add expression like this: | |||
| 2168 | /// | |||
| 2169 | /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r) | |||
| 2170 | /// | |||
| 2171 | /// where A and B are constants, update the map with these values: | |||
| 2172 | /// | |||
| 2173 | /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0) | |||
| 2174 | /// | |||
| 2175 | /// and add 13 + A*B*29 to AccumulatedConstant. | |||
| 2176 | /// This will allow getAddRecExpr to produce this: | |||
| 2177 | /// | |||
| 2178 | /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B) | |||
| 2179 | /// | |||
| 2180 | /// This form often exposes folding opportunities that are hidden in | |||
| 2181 | /// the original operand list. | |||
| 2182 | /// | |||
| 2183 | /// Return true iff it appears that any interesting folding opportunities | |||
| 2184 | /// may be exposed. This helps getAddRecExpr short-circuit extra work in | |||
| 2185 | /// the common case where no interesting opportunities are present, and | |||
| 2186 | /// is also used as a check to avoid infinite recursion. | |||
| 2187 | static bool | |||
| 2188 | CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M, | |||
| 2189 | SmallVectorImpl<const SCEV *> &NewOps, | |||
| 2190 | APInt &AccumulatedConstant, | |||
| 2191 | const SCEV *const *Ops, size_t NumOperands, | |||
| 2192 | const APInt &Scale, | |||
| 2193 | ScalarEvolution &SE) { | |||
| 2194 | bool Interesting = false; | |||
| 2195 | ||||
| 2196 | // Iterate over the add operands. They are sorted, with constants first. | |||
| 2197 | unsigned i = 0; | |||
| 2198 | while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) { | |||
| 2199 | ++i; | |||
| 2200 | // Pull a buried constant out to the outside. | |||
| 2201 | if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero()) | |||
| 2202 | Interesting = true; | |||
| 2203 | AccumulatedConstant += Scale * C->getAPInt(); | |||
| 2204 | } | |||
| 2205 | ||||
| 2206 | // Next comes everything else. We're especially interested in multiplies | |||
| 2207 | // here, but they're in the middle, so just visit the rest with one loop. | |||
| 2208 | for (; i != NumOperands; ++i) { | |||
| 2209 | const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]); | |||
| 2210 | if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) { | |||
| 2211 | APInt NewScale = | |||
| 2212 | Scale * cast<SCEVConstant>(Mul->getOperand(0))->getAPInt(); | |||
| 2213 | if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) { | |||
| 2214 | // A multiplication of a constant with another add; recurse. | |||
| 2215 | const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1)); | |||
| 2216 | Interesting |= | |||
| 2217 | CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant, | |||
| 2218 | Add->op_begin(), Add->getNumOperands(), | |||
| 2219 | NewScale, SE); | |||
| 2220 | } else { | |||
| 2221 | // A multiplication of a constant with some other value. Update | |||
| 2222 | // the map. | |||
| 2223 | SmallVector<const SCEV *, 4> MulOps(drop_begin(Mul->operands())); | |||
| 2224 | const SCEV *Key = SE.getMulExpr(MulOps); | |||
| 2225 | auto Pair = M.insert({Key, NewScale}); | |||
| 2226 | if (Pair.second) { | |||
| 2227 | NewOps.push_back(Pair.first->first); | |||
| 2228 | } else { | |||
| 2229 | Pair.first->second += NewScale; | |||
| 2230 | // The map already had an entry for this value, which may indicate | |||
| 2231 | // a folding opportunity. | |||
| 2232 | Interesting = true; | |||
| 2233 | } | |||
| 2234 | } | |||
| 2235 | } else { | |||
| 2236 | // An ordinary operand. Update the map. | |||
| 2237 | std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair = | |||
| 2238 | M.insert({Ops[i], Scale}); | |||
| 2239 | if (Pair.second) { | |||
| 2240 | NewOps.push_back(Pair.first->first); | |||
| 2241 | } else { | |||
| 2242 | Pair.first->second += Scale; | |||
| 2243 | // The map already had an entry for this value, which may indicate | |||
| 2244 | // a folding opportunity. | |||
| 2245 | Interesting = true; | |||
| 2246 | } | |||
| 2247 | } | |||
| 2248 | } | |||
| 2249 | ||||
| 2250 | return Interesting; | |||
| 2251 | } | |||
| 2252 | ||||
| 2253 | bool ScalarEvolution::willNotOverflow(Instruction::BinaryOps BinOp, bool Signed, | |||
| 2254 | const SCEV *LHS, const SCEV *RHS) { | |||
| 2255 | const SCEV *(ScalarEvolution::*Operation)(const SCEV *, const SCEV *, | |||
| 2256 | SCEV::NoWrapFlags, unsigned); | |||
| 2257 | switch (BinOp) { | |||
| 2258 | default: | |||
| 2259 | llvm_unreachable("Unsupported binary op")__builtin_unreachable(); | |||
| 2260 | case Instruction::Add: | |||
| 2261 | Operation = &ScalarEvolution::getAddExpr; | |||
| 2262 | break; | |||
| 2263 | case Instruction::Sub: | |||
| 2264 | Operation = &ScalarEvolution::getMinusSCEV; | |||
| 2265 | break; | |||
| 2266 | case Instruction::Mul: | |||
| 2267 | Operation = &ScalarEvolution::getMulExpr; | |||
| 2268 | break; | |||
| 2269 | } | |||
| 2270 | ||||
| 2271 | const SCEV *(ScalarEvolution::*Extension)(const SCEV *, Type *, unsigned) = | |||
| 2272 | Signed ? &ScalarEvolution::getSignExtendExpr | |||
| 2273 | : &ScalarEvolution::getZeroExtendExpr; | |||
| 2274 | ||||
| 2275 | // Check ext(LHS op RHS) == ext(LHS) op ext(RHS) | |||
| 2276 | auto *NarrowTy = cast<IntegerType>(LHS->getType()); | |||
| 2277 | auto *WideTy = | |||
| 2278 | IntegerType::get(NarrowTy->getContext(), NarrowTy->getBitWidth() * 2); | |||
| 2279 | ||||
| 2280 | const SCEV *A = (this->*Extension)( | |||
| 2281 | (this->*Operation)(LHS, RHS, SCEV::FlagAnyWrap, 0), WideTy, 0); | |||
| 2282 | const SCEV *B = (this->*Operation)((this->*Extension)(LHS, WideTy, 0), | |||
| 2283 | (this->*Extension)(RHS, WideTy, 0), | |||
| 2284 | SCEV::FlagAnyWrap, 0); | |||
| 2285 | return A == B; | |||
| 2286 | } | |||
| 2287 | ||||
| 2288 | std::pair<SCEV::NoWrapFlags, bool /*Deduced*/> | |||
| 2289 | ScalarEvolution::getStrengthenedNoWrapFlagsFromBinOp( | |||
| 2290 | const OverflowingBinaryOperator *OBO) { | |||
| 2291 | SCEV::NoWrapFlags Flags = SCEV::NoWrapFlags::FlagAnyWrap; | |||
| 2292 | ||||
| 2293 | if (OBO->hasNoUnsignedWrap()) | |||
| 2294 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW); | |||
| 2295 | if (OBO->hasNoSignedWrap()) | |||
| 2296 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW); | |||
| 2297 | ||||
| 2298 | bool Deduced = false; | |||
| 2299 | ||||
| 2300 | if (OBO->hasNoUnsignedWrap() && OBO->hasNoSignedWrap()) | |||
| 2301 | return {Flags, Deduced}; | |||
| 2302 | ||||
| 2303 | if (OBO->getOpcode() != Instruction::Add && | |||
| 2304 | OBO->getOpcode() != Instruction::Sub && | |||
| 2305 | OBO->getOpcode() != Instruction::Mul) | |||
| 2306 | return {Flags, Deduced}; | |||
| 2307 | ||||
| 2308 | const SCEV *LHS = getSCEV(OBO->getOperand(0)); | |||
| 2309 | const SCEV *RHS = getSCEV(OBO->getOperand(1)); | |||
| 2310 | ||||
| 2311 | if (!OBO->hasNoUnsignedWrap() && | |||
| 2312 | willNotOverflow((Instruction::BinaryOps)OBO->getOpcode(), | |||
| 2313 | /* Signed */ false, LHS, RHS)) { | |||
| 2314 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW); | |||
| 2315 | Deduced = true; | |||
| 2316 | } | |||
| 2317 | ||||
| 2318 | if (!OBO->hasNoSignedWrap() && | |||
| 2319 | willNotOverflow((Instruction::BinaryOps)OBO->getOpcode(), | |||
| 2320 | /* Signed */ true, LHS, RHS)) { | |||
| 2321 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW); | |||
| 2322 | Deduced = true; | |||
| 2323 | } | |||
| 2324 | ||||
| 2325 | return {Flags, Deduced}; | |||
| 2326 | } | |||
| 2327 | ||||
| 2328 | // We're trying to construct a SCEV of type `Type' with `Ops' as operands and | |||
| 2329 | // `OldFlags' as can't-wrap behavior. Infer a more aggressive set of | |||
| 2330 | // can't-overflow flags for the operation if possible. | |||
| 2331 | static SCEV::NoWrapFlags | |||
| 2332 | StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type, | |||
| 2333 | const ArrayRef<const SCEV *> Ops, | |||
| 2334 | SCEV::NoWrapFlags Flags) { | |||
| 2335 | using namespace std::placeholders; | |||
| 2336 | ||||
| 2337 | using OBO = OverflowingBinaryOperator; | |||
| 2338 | ||||
| 2339 | bool CanAnalyze = | |||
| 2340 | Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr; | |||
| 2341 | (void)CanAnalyze; | |||
| 2342 | assert(CanAnalyze && "don't call from other places!")((void)0); | |||
| 2343 | ||||
| 2344 | int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW; | |||
| 2345 | SCEV::NoWrapFlags SignOrUnsignWrap = | |||
| 2346 | ScalarEvolution::maskFlags(Flags, SignOrUnsignMask); | |||
| 2347 | ||||
| 2348 | // If FlagNSW is true and all the operands are non-negative, infer FlagNUW. | |||
| 2349 | auto IsKnownNonNegative = [&](const SCEV *S) { | |||
| 2350 | return SE->isKnownNonNegative(S); | |||
| 2351 | }; | |||
| 2352 | ||||
| 2353 | if (SignOrUnsignWrap == SCEV::FlagNSW && all_of(Ops, IsKnownNonNegative)) | |||
| 2354 | Flags = | |||
| 2355 | ScalarEvolution::setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask); | |||
| 2356 | ||||
| 2357 | SignOrUnsignWrap = ScalarEvolution::maskFlags(Flags, SignOrUnsignMask); | |||
| 2358 | ||||
| 2359 | if (SignOrUnsignWrap != SignOrUnsignMask && | |||
| 2360 | (Type == scAddExpr || Type == scMulExpr) && Ops.size() == 2 && | |||
| 2361 | isa<SCEVConstant>(Ops[0])) { | |||
| 2362 | ||||
| 2363 | auto Opcode = [&] { | |||
| 2364 | switch (Type) { | |||
| 2365 | case scAddExpr: | |||
| 2366 | return Instruction::Add; | |||
| 2367 | case scMulExpr: | |||
| 2368 | return Instruction::Mul; | |||
| 2369 | default: | |||
| 2370 | llvm_unreachable("Unexpected SCEV op.")__builtin_unreachable(); | |||
| 2371 | } | |||
| 2372 | }(); | |||
| 2373 | ||||
| 2374 | const APInt &C = cast<SCEVConstant>(Ops[0])->getAPInt(); | |||
| 2375 | ||||
| 2376 | // (A <opcode> C) --> (A <opcode> C)<nsw> if the op doesn't sign overflow. | |||
| 2377 | if (!(SignOrUnsignWrap & SCEV::FlagNSW)) { | |||
| 2378 | auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion( | |||
| 2379 | Opcode, C, OBO::NoSignedWrap); | |||
| 2380 | if (NSWRegion.contains(SE->getSignedRange(Ops[1]))) | |||
| 2381 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW); | |||
| 2382 | } | |||
| 2383 | ||||
| 2384 | // (A <opcode> C) --> (A <opcode> C)<nuw> if the op doesn't unsign overflow. | |||
| 2385 | if (!(SignOrUnsignWrap & SCEV::FlagNUW)) { | |||
| 2386 | auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion( | |||
| 2387 | Opcode, C, OBO::NoUnsignedWrap); | |||
| 2388 | if (NUWRegion.contains(SE->getUnsignedRange(Ops[1]))) | |||
| 2389 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW); | |||
| 2390 | } | |||
| 2391 | } | |||
| 2392 | ||||
| 2393 | return Flags; | |||
| 2394 | } | |||
| 2395 | ||||
| 2396 | bool ScalarEvolution::isAvailableAtLoopEntry(const SCEV *S, const Loop *L) { | |||
| 2397 | return isLoopInvariant(S, L) && properlyDominates(S, L->getHeader()); | |||
| 2398 | } | |||
| 2399 | ||||
| 2400 | /// Get a canonical add expression, or something simpler if possible. | |||
| 2401 | const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops, | |||
| 2402 | SCEV::NoWrapFlags OrigFlags, | |||
| 2403 | unsigned Depth) { | |||
| 2404 | assert(!(OrigFlags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&((void)0) | |||
| 2405 | "only nuw or nsw allowed")((void)0); | |||
| 2406 | assert(!Ops.empty() && "Cannot get empty add!")((void)0); | |||
| 2407 | if (Ops.size() == 1) return Ops[0]; | |||
| 2408 | #ifndef NDEBUG1 | |||
| 2409 | Type *ETy = getEffectiveSCEVType(Ops[0]->getType()); | |||
| 2410 | for (unsigned i = 1, e = Ops.size(); i != e; ++i) | |||
| 2411 | assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((void)0) | |||
| 2412 | "SCEVAddExpr operand types don't match!")((void)0); | |||
| 2413 | unsigned NumPtrs = count_if( | |||
| 2414 | Ops, [](const SCEV *Op) { return Op->getType()->isPointerTy(); }); | |||
| 2415 | assert(NumPtrs <= 1 && "add has at most one pointer operand")((void)0); | |||
| 2416 | #endif | |||
| 2417 | ||||
| 2418 | // Sort by complexity, this groups all similar expression types together. | |||
| 2419 | GroupByComplexity(Ops, &LI, DT); | |||
| 2420 | ||||
| 2421 | // If there are any constants, fold them together. | |||
| 2422 | unsigned Idx = 0; | |||
| 2423 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) { | |||
| 2424 | ++Idx; | |||
| 2425 | assert(Idx < Ops.size())((void)0); | |||
| 2426 | while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) { | |||
| 2427 | // We found two constants, fold them together! | |||
| 2428 | Ops[0] = getConstant(LHSC->getAPInt() + RHSC->getAPInt()); | |||
| 2429 | if (Ops.size() == 2) return Ops[0]; | |||
| 2430 | Ops.erase(Ops.begin()+1); // Erase the folded element | |||
| 2431 | LHSC = cast<SCEVConstant>(Ops[0]); | |||
| 2432 | } | |||
| 2433 | ||||
| 2434 | // If we are left with a constant zero being added, strip it off. | |||
| 2435 | if (LHSC->getValue()->isZero()) { | |||
| 2436 | Ops.erase(Ops.begin()); | |||
| 2437 | --Idx; | |||
| 2438 | } | |||
| 2439 | ||||
| 2440 | if (Ops.size() == 1) return Ops[0]; | |||
| 2441 | } | |||
| 2442 | ||||
| 2443 | // Delay expensive flag strengthening until necessary. | |||
| 2444 | auto ComputeFlags = [this, OrigFlags](const ArrayRef<const SCEV *> Ops) { | |||
| 2445 | return StrengthenNoWrapFlags(this, scAddExpr, Ops, OrigFlags); | |||
| 2446 | }; | |||
| 2447 | ||||
| 2448 | // Limit recursion calls depth. | |||
| 2449 | if (Depth > MaxArithDepth || hasHugeExpression(Ops)) | |||
| 2450 | return getOrCreateAddExpr(Ops, ComputeFlags(Ops)); | |||
| 2451 | ||||
| 2452 | if (SCEV *S = std::get<0>(findExistingSCEVInCache(scAddExpr, Ops))) { | |||
| 2453 | // Don't strengthen flags if we have no new information. | |||
| 2454 | SCEVAddExpr *Add = static_cast<SCEVAddExpr *>(S); | |||
| 2455 | if (Add->getNoWrapFlags(OrigFlags) != OrigFlags) | |||
| 2456 | Add->setNoWrapFlags(ComputeFlags(Ops)); | |||
| 2457 | return S; | |||
| 2458 | } | |||
| 2459 | ||||
| 2460 | // Okay, check to see if the same value occurs in the operand list more than | |||
| 2461 | // once. If so, merge them together into an multiply expression. Since we | |||
| 2462 | // sorted the list, these values are required to be adjacent. | |||
| 2463 | Type *Ty = Ops[0]->getType(); | |||
| 2464 | bool FoundMatch = false; | |||
| 2465 | for (unsigned i = 0, e = Ops.size(); i != e-1; ++i) | |||
| 2466 | if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2 | |||
| 2467 | // Scan ahead to count how many equal operands there are. | |||
| 2468 | unsigned Count = 2; | |||
| 2469 | while (i+Count != e && Ops[i+Count] == Ops[i]) | |||
| 2470 | ++Count; | |||
| 2471 | // Merge the values into a multiply. | |||
| 2472 | const SCEV *Scale = getConstant(Ty, Count); | |||
| 2473 | const SCEV *Mul = getMulExpr(Scale, Ops[i], SCEV::FlagAnyWrap, Depth + 1); | |||
| 2474 | if (Ops.size() == Count) | |||
| 2475 | return Mul; | |||
| 2476 | Ops[i] = Mul; | |||
| 2477 | Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count); | |||
| 2478 | --i; e -= Count - 1; | |||
| 2479 | FoundMatch = true; | |||
| 2480 | } | |||
| 2481 | if (FoundMatch) | |||
| 2482 | return getAddExpr(Ops, OrigFlags, Depth + 1); | |||
| 2483 | ||||
| 2484 | // Check for truncates. If all the operands are truncated from the same | |||
| 2485 | // type, see if factoring out the truncate would permit the result to be | |||
| 2486 | // folded. eg., n*trunc(x) + m*trunc(y) --> trunc(trunc(m)*x + trunc(n)*y) | |||
| 2487 | // if the contents of the resulting outer trunc fold to something simple. | |||
| 2488 | auto FindTruncSrcType = [&]() -> Type * { | |||
| 2489 | // We're ultimately looking to fold an addrec of truncs and muls of only | |||
| 2490 | // constants and truncs, so if we find any other types of SCEV | |||
| 2491 | // as operands of the addrec then we bail and return nullptr here. | |||
| 2492 | // Otherwise, we return the type of the operand of a trunc that we find. | |||
| 2493 | if (auto *T = dyn_cast<SCEVTruncateExpr>(Ops[Idx])) | |||
| 2494 | return T->getOperand()->getType(); | |||
| 2495 | if (const auto *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) { | |||
| 2496 | const auto *LastOp = Mul->getOperand(Mul->getNumOperands() - 1); | |||
| 2497 | if (const auto *T = dyn_cast<SCEVTruncateExpr>(LastOp)) | |||
| 2498 | return T->getOperand()->getType(); | |||
| 2499 | } | |||
| 2500 | return nullptr; | |||
| 2501 | }; | |||
| 2502 | if (auto *SrcType = FindTruncSrcType()) { | |||
| 2503 | SmallVector<const SCEV *, 8> LargeOps; | |||
| 2504 | bool Ok = true; | |||
| 2505 | // Check all the operands to see if they can be represented in the | |||
| 2506 | // source type of the truncate. | |||
| 2507 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) { | |||
| 2508 | if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) { | |||
| 2509 | if (T->getOperand()->getType() != SrcType) { | |||
| 2510 | Ok = false; | |||
| 2511 | break; | |||
| 2512 | } | |||
| 2513 | LargeOps.push_back(T->getOperand()); | |||
| 2514 | } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) { | |||
| 2515 | LargeOps.push_back(getAnyExtendExpr(C, SrcType)); | |||
| 2516 | } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) { | |||
| 2517 | SmallVector<const SCEV *, 8> LargeMulOps; | |||
| 2518 | for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) { | |||
| 2519 | if (const SCEVTruncateExpr *T = | |||
| 2520 | dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) { | |||
| 2521 | if (T->getOperand()->getType() != SrcType) { | |||
| 2522 | Ok = false; | |||
| 2523 | break; | |||
| 2524 | } | |||
| 2525 | LargeMulOps.push_back(T->getOperand()); | |||
| 2526 | } else if (const auto *C = dyn_cast<SCEVConstant>(M->getOperand(j))) { | |||
| 2527 | LargeMulOps.push_back(getAnyExtendExpr(C, SrcType)); | |||
| 2528 | } else { | |||
| 2529 | Ok = false; | |||
| 2530 | break; | |||
| 2531 | } | |||
| 2532 | } | |||
| 2533 | if (Ok) | |||
| 2534 | LargeOps.push_back(getMulExpr(LargeMulOps, SCEV::FlagAnyWrap, Depth + 1)); | |||
| 2535 | } else { | |||
| 2536 | Ok = false; | |||
| 2537 | break; | |||
| 2538 | } | |||
| 2539 | } | |||
| 2540 | if (Ok) { | |||
| 2541 | // Evaluate the expression in the larger type. | |||
| 2542 | const SCEV *Fold = getAddExpr(LargeOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2543 | // If it folds to something simple, use it. Otherwise, don't. | |||
| 2544 | if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold)) | |||
| 2545 | return getTruncateExpr(Fold, Ty); | |||
| 2546 | } | |||
| 2547 | } | |||
| 2548 | ||||
| 2549 | if (Ops.size() == 2) { | |||
| 2550 | // Check if we have an expression of the form ((X + C1) - C2), where C1 and | |||
| 2551 | // C2 can be folded in a way that allows retaining wrapping flags of (X + | |||
| 2552 | // C1). | |||
| 2553 | const SCEV *A = Ops[0]; | |||
| 2554 | const SCEV *B = Ops[1]; | |||
| 2555 | auto *AddExpr = dyn_cast<SCEVAddExpr>(B); | |||
| 2556 | auto *C = dyn_cast<SCEVConstant>(A); | |||
| 2557 | if (AddExpr && C && isa<SCEVConstant>(AddExpr->getOperand(0))) { | |||
| 2558 | auto C1 = cast<SCEVConstant>(AddExpr->getOperand(0))->getAPInt(); | |||
| 2559 | auto C2 = C->getAPInt(); | |||
| 2560 | SCEV::NoWrapFlags PreservedFlags = SCEV::FlagAnyWrap; | |||
| 2561 | ||||
| 2562 | APInt ConstAdd = C1 + C2; | |||
| 2563 | auto AddFlags = AddExpr->getNoWrapFlags(); | |||
| 2564 | // Adding a smaller constant is NUW if the original AddExpr was NUW. | |||
| 2565 | if (ScalarEvolution::maskFlags(AddFlags, SCEV::FlagNUW) == | |||
| 2566 | SCEV::FlagNUW && | |||
| 2567 | ConstAdd.ule(C1)) { | |||
| 2568 | PreservedFlags = | |||
| 2569 | ScalarEvolution::setFlags(PreservedFlags, SCEV::FlagNUW); | |||
| 2570 | } | |||
| 2571 | ||||
| 2572 | // Adding a constant with the same sign and small magnitude is NSW, if the | |||
| 2573 | // original AddExpr was NSW. | |||
| 2574 | if (ScalarEvolution::maskFlags(AddFlags, SCEV::FlagNSW) == | |||
| 2575 | SCEV::FlagNSW && | |||
| 2576 | C1.isSignBitSet() == ConstAdd.isSignBitSet() && | |||
| 2577 | ConstAdd.abs().ule(C1.abs())) { | |||
| 2578 | PreservedFlags = | |||
| 2579 | ScalarEvolution::setFlags(PreservedFlags, SCEV::FlagNSW); | |||
| 2580 | } | |||
| 2581 | ||||
| 2582 | if (PreservedFlags != SCEV::FlagAnyWrap) { | |||
| 2583 | SmallVector<const SCEV *, 4> NewOps(AddExpr->op_begin(), | |||
| 2584 | AddExpr->op_end()); | |||
| 2585 | NewOps[0] = getConstant(ConstAdd); | |||
| 2586 | return getAddExpr(NewOps, PreservedFlags); | |||
| 2587 | } | |||
| 2588 | } | |||
| 2589 | } | |||
| 2590 | ||||
| 2591 | // Skip past any other cast SCEVs. | |||
| 2592 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr) | |||
| 2593 | ++Idx; | |||
| 2594 | ||||
| 2595 | // If there are add operands they would be next. | |||
| 2596 | if (Idx < Ops.size()) { | |||
| 2597 | bool DeletedAdd = false; | |||
| 2598 | // If the original flags and all inlined SCEVAddExprs are NUW, use the | |||
| 2599 | // common NUW flag for expression after inlining. Other flags cannot be | |||
| 2600 | // preserved, because they may depend on the original order of operations. | |||
| 2601 | SCEV::NoWrapFlags CommonFlags = maskFlags(OrigFlags, SCEV::FlagNUW); | |||
| 2602 | while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) { | |||
| 2603 | if (Ops.size() > AddOpsInlineThreshold || | |||
| 2604 | Add->getNumOperands() > AddOpsInlineThreshold) | |||
| 2605 | break; | |||
| 2606 | // If we have an add, expand the add operands onto the end of the operands | |||
| 2607 | // list. | |||
| 2608 | Ops.erase(Ops.begin()+Idx); | |||
| 2609 | Ops.append(Add->op_begin(), Add->op_end()); | |||
| 2610 | DeletedAdd = true; | |||
| 2611 | CommonFlags = maskFlags(CommonFlags, Add->getNoWrapFlags()); | |||
| 2612 | } | |||
| 2613 | ||||
| 2614 | // If we deleted at least one add, we added operands to the end of the list, | |||
| 2615 | // and they are not necessarily sorted. Recurse to resort and resimplify | |||
| 2616 | // any operands we just acquired. | |||
| 2617 | if (DeletedAdd) | |||
| 2618 | return getAddExpr(Ops, CommonFlags, Depth + 1); | |||
| 2619 | } | |||
| 2620 | ||||
| 2621 | // Skip over the add expression until we get to a multiply. | |||
| 2622 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr) | |||
| 2623 | ++Idx; | |||
| 2624 | ||||
| 2625 | // Check to see if there are any folding opportunities present with | |||
| 2626 | // operands multiplied by constant values. | |||
| 2627 | if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) { | |||
| 2628 | uint64_t BitWidth = getTypeSizeInBits(Ty); | |||
| 2629 | DenseMap<const SCEV *, APInt> M; | |||
| 2630 | SmallVector<const SCEV *, 8> NewOps; | |||
| 2631 | APInt AccumulatedConstant(BitWidth, 0); | |||
| 2632 | if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant, | |||
| 2633 | Ops.data(), Ops.size(), | |||
| 2634 | APInt(BitWidth, 1), *this)) { | |||
| 2635 | struct APIntCompare { | |||
| 2636 | bool operator()(const APInt &LHS, const APInt &RHS) const { | |||
| 2637 | return LHS.ult(RHS); | |||
| 2638 | } | |||
| 2639 | }; | |||
| 2640 | ||||
| 2641 | // Some interesting folding opportunity is present, so its worthwhile to | |||
| 2642 | // re-generate the operands list. Group the operands by constant scale, | |||
| 2643 | // to avoid multiplying by the same constant scale multiple times. | |||
| 2644 | std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists; | |||
| 2645 | for (const SCEV *NewOp : NewOps) | |||
| 2646 | MulOpLists[M.find(NewOp)->second].push_back(NewOp); | |||
| 2647 | // Re-generate the operands list. | |||
| 2648 | Ops.clear(); | |||
| 2649 | if (AccumulatedConstant != 0) | |||
| 2650 | Ops.push_back(getConstant(AccumulatedConstant)); | |||
| 2651 | for (auto &MulOp : MulOpLists) { | |||
| 2652 | if (MulOp.first == 1) { | |||
| 2653 | Ops.push_back(getAddExpr(MulOp.second, SCEV::FlagAnyWrap, Depth + 1)); | |||
| 2654 | } else if (MulOp.first != 0) { | |||
| 2655 | Ops.push_back(getMulExpr( | |||
| 2656 | getConstant(MulOp.first), | |||
| 2657 | getAddExpr(MulOp.second, SCEV::FlagAnyWrap, Depth + 1), | |||
| 2658 | SCEV::FlagAnyWrap, Depth + 1)); | |||
| 2659 | } | |||
| 2660 | } | |||
| 2661 | if (Ops.empty()) | |||
| 2662 | return getZero(Ty); | |||
| 2663 | if (Ops.size() == 1) | |||
| 2664 | return Ops[0]; | |||
| 2665 | return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2666 | } | |||
| 2667 | } | |||
| 2668 | ||||
| 2669 | // If we are adding something to a multiply expression, make sure the | |||
| 2670 | // something is not already an operand of the multiply. If so, merge it into | |||
| 2671 | // the multiply. | |||
| 2672 | for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) { | |||
| 2673 | const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]); | |||
| 2674 | for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) { | |||
| 2675 | const SCEV *MulOpSCEV = Mul->getOperand(MulOp); | |||
| 2676 | if (isa<SCEVConstant>(MulOpSCEV)) | |||
| 2677 | continue; | |||
| 2678 | for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp) | |||
| 2679 | if (MulOpSCEV == Ops[AddOp]) { | |||
| 2680 | // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1)) | |||
| 2681 | const SCEV *InnerMul = Mul->getOperand(MulOp == 0); | |||
| 2682 | if (Mul->getNumOperands() != 2) { | |||
| 2683 | // If the multiply has more than two operands, we must get the | |||
| 2684 | // Y*Z term. | |||
| 2685 | SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(), | |||
| 2686 | Mul->op_begin()+MulOp); | |||
| 2687 | MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end()); | |||
| 2688 | InnerMul = getMulExpr(MulOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2689 | } | |||
| 2690 | SmallVector<const SCEV *, 2> TwoOps = {getOne(Ty), InnerMul}; | |||
| 2691 | const SCEV *AddOne = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2692 | const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV, | |||
| 2693 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 2694 | if (Ops.size() == 2) return OuterMul; | |||
| 2695 | if (AddOp < Idx) { | |||
| 2696 | Ops.erase(Ops.begin()+AddOp); | |||
| 2697 | Ops.erase(Ops.begin()+Idx-1); | |||
| 2698 | } else { | |||
| 2699 | Ops.erase(Ops.begin()+Idx); | |||
| 2700 | Ops.erase(Ops.begin()+AddOp-1); | |||
| 2701 | } | |||
| 2702 | Ops.push_back(OuterMul); | |||
| 2703 | return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2704 | } | |||
| 2705 | ||||
| 2706 | // Check this multiply against other multiplies being added together. | |||
| 2707 | for (unsigned OtherMulIdx = Idx+1; | |||
| 2708 | OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]); | |||
| 2709 | ++OtherMulIdx) { | |||
| 2710 | const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]); | |||
| 2711 | // If MulOp occurs in OtherMul, we can fold the two multiplies | |||
| 2712 | // together. | |||
| 2713 | for (unsigned OMulOp = 0, e = OtherMul->getNumOperands(); | |||
| 2714 | OMulOp != e; ++OMulOp) | |||
| 2715 | if (OtherMul->getOperand(OMulOp) == MulOpSCEV) { | |||
| 2716 | // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E)) | |||
| 2717 | const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0); | |||
| 2718 | if (Mul->getNumOperands() != 2) { | |||
| 2719 | SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(), | |||
| 2720 | Mul->op_begin()+MulOp); | |||
| 2721 | MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end()); | |||
| 2722 | InnerMul1 = getMulExpr(MulOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2723 | } | |||
| 2724 | const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0); | |||
| 2725 | if (OtherMul->getNumOperands() != 2) { | |||
| 2726 | SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(), | |||
| 2727 | OtherMul->op_begin()+OMulOp); | |||
| 2728 | MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end()); | |||
| 2729 | InnerMul2 = getMulExpr(MulOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2730 | } | |||
| 2731 | SmallVector<const SCEV *, 2> TwoOps = {InnerMul1, InnerMul2}; | |||
| 2732 | const SCEV *InnerMulSum = | |||
| 2733 | getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2734 | const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum, | |||
| 2735 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 2736 | if (Ops.size() == 2) return OuterMul; | |||
| 2737 | Ops.erase(Ops.begin()+Idx); | |||
| 2738 | Ops.erase(Ops.begin()+OtherMulIdx-1); | |||
| 2739 | Ops.push_back(OuterMul); | |||
| 2740 | return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2741 | } | |||
| 2742 | } | |||
| 2743 | } | |||
| 2744 | } | |||
| 2745 | ||||
| 2746 | // If there are any add recurrences in the operands list, see if any other | |||
| 2747 | // added values are loop invariant. If so, we can fold them into the | |||
| 2748 | // recurrence. | |||
| 2749 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr) | |||
| 2750 | ++Idx; | |||
| 2751 | ||||
| 2752 | // Scan over all recurrences, trying to fold loop invariants into them. | |||
| 2753 | for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) { | |||
| 2754 | // Scan all of the other operands to this add and add them to the vector if | |||
| 2755 | // they are loop invariant w.r.t. the recurrence. | |||
| 2756 | SmallVector<const SCEV *, 8> LIOps; | |||
| 2757 | const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]); | |||
| 2758 | const Loop *AddRecLoop = AddRec->getLoop(); | |||
| 2759 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) | |||
| 2760 | if (isAvailableAtLoopEntry(Ops[i], AddRecLoop)) { | |||
| 2761 | LIOps.push_back(Ops[i]); | |||
| 2762 | Ops.erase(Ops.begin()+i); | |||
| 2763 | --i; --e; | |||
| 2764 | } | |||
| 2765 | ||||
| 2766 | // If we found some loop invariants, fold them into the recurrence. | |||
| 2767 | if (!LIOps.empty()) { | |||
| 2768 | // Compute nowrap flags for the addition of the loop-invariant ops and | |||
| 2769 | // the addrec. Temporarily push it as an operand for that purpose. | |||
| 2770 | LIOps.push_back(AddRec); | |||
| 2771 | SCEV::NoWrapFlags Flags = ComputeFlags(LIOps); | |||
| 2772 | LIOps.pop_back(); | |||
| 2773 | ||||
| 2774 | // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step} | |||
| 2775 | LIOps.push_back(AddRec->getStart()); | |||
| 2776 | ||||
| 2777 | SmallVector<const SCEV *, 4> AddRecOps(AddRec->operands()); | |||
| 2778 | // This follows from the fact that the no-wrap flags on the outer add | |||
| 2779 | // expression are applicable on the 0th iteration, when the add recurrence | |||
| 2780 | // will be equal to its start value. | |||
| 2781 | AddRecOps[0] = getAddExpr(LIOps, Flags, Depth + 1); | |||
| 2782 | ||||
| 2783 | // Build the new addrec. Propagate the NUW and NSW flags if both the | |||
| 2784 | // outer add and the inner addrec are guaranteed to have no overflow. | |||
| 2785 | // Always propagate NW. | |||
| 2786 | Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW)); | |||
| 2787 | const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags); | |||
| 2788 | ||||
| 2789 | // If all of the other operands were loop invariant, we are done. | |||
| 2790 | if (Ops.size() == 1) return NewRec; | |||
| 2791 | ||||
| 2792 | // Otherwise, add the folded AddRec by the non-invariant parts. | |||
| 2793 | for (unsigned i = 0;; ++i) | |||
| 2794 | if (Ops[i] == AddRec) { | |||
| 2795 | Ops[i] = NewRec; | |||
| 2796 | break; | |||
| 2797 | } | |||
| 2798 | return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2799 | } | |||
| 2800 | ||||
| 2801 | // Okay, if there weren't any loop invariants to be folded, check to see if | |||
| 2802 | // there are multiple AddRec's with the same loop induction variable being | |||
| 2803 | // added together. If so, we can fold them. | |||
| 2804 | for (unsigned OtherIdx = Idx+1; | |||
| 2805 | OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]); | |||
| 2806 | ++OtherIdx) { | |||
| 2807 | // We expect the AddRecExpr's to be sorted in reverse dominance order, | |||
| 2808 | // so that the 1st found AddRecExpr is dominated by all others. | |||
| 2809 | assert(DT.dominates(((void)0) | |||
| 2810 | cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()->getHeader(),((void)0) | |||
| 2811 | AddRec->getLoop()->getHeader()) &&((void)0) | |||
| 2812 | "AddRecExprs are not sorted in reverse dominance order?")((void)0); | |||
| 2813 | if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) { | |||
| 2814 | // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L> | |||
| 2815 | SmallVector<const SCEV *, 4> AddRecOps(AddRec->operands()); | |||
| 2816 | for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]); | |||
| 2817 | ++OtherIdx) { | |||
| 2818 | const auto *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]); | |||
| 2819 | if (OtherAddRec->getLoop() == AddRecLoop) { | |||
| 2820 | for (unsigned i = 0, e = OtherAddRec->getNumOperands(); | |||
| 2821 | i != e; ++i) { | |||
| 2822 | if (i >= AddRecOps.size()) { | |||
| 2823 | AddRecOps.append(OtherAddRec->op_begin()+i, | |||
| 2824 | OtherAddRec->op_end()); | |||
| 2825 | break; | |||
| 2826 | } | |||
| 2827 | SmallVector<const SCEV *, 2> TwoOps = { | |||
| 2828 | AddRecOps[i], OtherAddRec->getOperand(i)}; | |||
| 2829 | AddRecOps[i] = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2830 | } | |||
| 2831 | Ops.erase(Ops.begin() + OtherIdx); --OtherIdx; | |||
| 2832 | } | |||
| 2833 | } | |||
| 2834 | // Step size has changed, so we cannot guarantee no self-wraparound. | |||
| 2835 | Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap); | |||
| 2836 | return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 2837 | } | |||
| 2838 | } | |||
| 2839 | ||||
| 2840 | // Otherwise couldn't fold anything into this recurrence. Move onto the | |||
| 2841 | // next one. | |||
| 2842 | } | |||
| 2843 | ||||
| 2844 | // Okay, it looks like we really DO need an add expr. Check to see if we | |||
| 2845 | // already have one, otherwise create a new one. | |||
| 2846 | return getOrCreateAddExpr(Ops, ComputeFlags(Ops)); | |||
| 2847 | } | |||
| 2848 | ||||
| 2849 | const SCEV * | |||
| 2850 | ScalarEvolution::getOrCreateAddExpr(ArrayRef<const SCEV *> Ops, | |||
| 2851 | SCEV::NoWrapFlags Flags) { | |||
| 2852 | FoldingSetNodeID ID; | |||
| 2853 | ID.AddInteger(scAddExpr); | |||
| 2854 | for (const SCEV *Op : Ops) | |||
| 2855 | ID.AddPointer(Op); | |||
| 2856 | void *IP = nullptr; | |||
| 2857 | SCEVAddExpr *S = | |||
| 2858 | static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP)); | |||
| 2859 | if (!S) { | |||
| 2860 | const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size()); | |||
| 2861 | std::uninitialized_copy(Ops.begin(), Ops.end(), O); | |||
| 2862 | S = new (SCEVAllocator) | |||
| 2863 | SCEVAddExpr(ID.Intern(SCEVAllocator), O, Ops.size()); | |||
| 2864 | UniqueSCEVs.InsertNode(S, IP); | |||
| 2865 | addToLoopUseLists(S); | |||
| 2866 | } | |||
| 2867 | S->setNoWrapFlags(Flags); | |||
| 2868 | return S; | |||
| 2869 | } | |||
| 2870 | ||||
| 2871 | const SCEV * | |||
| 2872 | ScalarEvolution::getOrCreateAddRecExpr(ArrayRef<const SCEV *> Ops, | |||
| 2873 | const Loop *L, SCEV::NoWrapFlags Flags) { | |||
| 2874 | FoldingSetNodeID ID; | |||
| 2875 | ID.AddInteger(scAddRecExpr); | |||
| 2876 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) | |||
| 2877 | ID.AddPointer(Ops[i]); | |||
| 2878 | ID.AddPointer(L); | |||
| 2879 | void *IP = nullptr; | |||
| 2880 | SCEVAddRecExpr *S = | |||
| 2881 | static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP)); | |||
| 2882 | if (!S) { | |||
| 2883 | const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size()); | |||
| 2884 | std::uninitialized_copy(Ops.begin(), Ops.end(), O); | |||
| 2885 | S = new (SCEVAllocator) | |||
| 2886 | SCEVAddRecExpr(ID.Intern(SCEVAllocator), O, Ops.size(), L); | |||
| 2887 | UniqueSCEVs.InsertNode(S, IP); | |||
| 2888 | addToLoopUseLists(S); | |||
| 2889 | } | |||
| 2890 | setNoWrapFlags(S, Flags); | |||
| 2891 | return S; | |||
| 2892 | } | |||
| 2893 | ||||
| 2894 | const SCEV * | |||
| 2895 | ScalarEvolution::getOrCreateMulExpr(ArrayRef<const SCEV *> Ops, | |||
| 2896 | SCEV::NoWrapFlags Flags) { | |||
| 2897 | FoldingSetNodeID ID; | |||
| 2898 | ID.AddInteger(scMulExpr); | |||
| 2899 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) | |||
| 2900 | ID.AddPointer(Ops[i]); | |||
| 2901 | void *IP = nullptr; | |||
| 2902 | SCEVMulExpr *S = | |||
| 2903 | static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP)); | |||
| 2904 | if (!S) { | |||
| 2905 | const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size()); | |||
| 2906 | std::uninitialized_copy(Ops.begin(), Ops.end(), O); | |||
| 2907 | S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator), | |||
| 2908 | O, Ops.size()); | |||
| 2909 | UniqueSCEVs.InsertNode(S, IP); | |||
| 2910 | addToLoopUseLists(S); | |||
| 2911 | } | |||
| 2912 | S->setNoWrapFlags(Flags); | |||
| 2913 | return S; | |||
| 2914 | } | |||
| 2915 | ||||
| 2916 | static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) { | |||
| 2917 | uint64_t k = i*j; | |||
| 2918 | if (j > 1 && k / j != i) Overflow = true; | |||
| 2919 | return k; | |||
| 2920 | } | |||
| 2921 | ||||
| 2922 | /// Compute the result of "n choose k", the binomial coefficient. If an | |||
| 2923 | /// intermediate computation overflows, Overflow will be set and the return will | |||
| 2924 | /// be garbage. Overflow is not cleared on absence of overflow. | |||
| 2925 | static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) { | |||
| 2926 | // We use the multiplicative formula: | |||
| 2927 | // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 . | |||
| 2928 | // At each iteration, we take the n-th term of the numeral and divide by the | |||
| 2929 | // (k-n)th term of the denominator. This division will always produce an | |||
| 2930 | // integral result, and helps reduce the chance of overflow in the | |||
| 2931 | // intermediate computations. However, we can still overflow even when the | |||
| 2932 | // final result would fit. | |||
| 2933 | ||||
| 2934 | if (n == 0 || n == k) return 1; | |||
| 2935 | if (k > n) return 0; | |||
| 2936 | ||||
| 2937 | if (k > n/2) | |||
| 2938 | k = n-k; | |||
| 2939 | ||||
| 2940 | uint64_t r = 1; | |||
| 2941 | for (uint64_t i = 1; i <= k; ++i) { | |||
| 2942 | r = umul_ov(r, n-(i-1), Overflow); | |||
| 2943 | r /= i; | |||
| 2944 | } | |||
| 2945 | return r; | |||
| 2946 | } | |||
| 2947 | ||||
| 2948 | /// Determine if any of the operands in this SCEV are a constant or if | |||
| 2949 | /// any of the add or multiply expressions in this SCEV contain a constant. | |||
| 2950 | static bool containsConstantInAddMulChain(const SCEV *StartExpr) { | |||
| 2951 | struct FindConstantInAddMulChain { | |||
| 2952 | bool FoundConstant = false; | |||
| 2953 | ||||
| 2954 | bool follow(const SCEV *S) { | |||
| 2955 | FoundConstant |= isa<SCEVConstant>(S); | |||
| 2956 | return isa<SCEVAddExpr>(S) || isa<SCEVMulExpr>(S); | |||
| 2957 | } | |||
| 2958 | ||||
| 2959 | bool isDone() const { | |||
| 2960 | return FoundConstant; | |||
| 2961 | } | |||
| 2962 | }; | |||
| 2963 | ||||
| 2964 | FindConstantInAddMulChain F; | |||
| 2965 | SCEVTraversal<FindConstantInAddMulChain> ST(F); | |||
| 2966 | ST.visitAll(StartExpr); | |||
| 2967 | return F.FoundConstant; | |||
| 2968 | } | |||
| 2969 | ||||
| 2970 | /// Get a canonical multiply expression, or something simpler if possible. | |||
| 2971 | const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops, | |||
| 2972 | SCEV::NoWrapFlags OrigFlags, | |||
| 2973 | unsigned Depth) { | |||
| 2974 | assert(OrigFlags == maskFlags(OrigFlags, SCEV::FlagNUW | SCEV::FlagNSW) &&((void)0) | |||
| 2975 | "only nuw or nsw allowed")((void)0); | |||
| 2976 | assert(!Ops.empty() && "Cannot get empty mul!")((void)0); | |||
| 2977 | if (Ops.size() == 1) return Ops[0]; | |||
| 2978 | #ifndef NDEBUG1 | |||
| 2979 | Type *ETy = Ops[0]->getType(); | |||
| 2980 | assert(!ETy->isPointerTy())((void)0); | |||
| 2981 | for (unsigned i = 1, e = Ops.size(); i != e; ++i) | |||
| 2982 | assert(Ops[i]->getType() == ETy &&((void)0) | |||
| 2983 | "SCEVMulExpr operand types don't match!")((void)0); | |||
| 2984 | #endif | |||
| 2985 | ||||
| 2986 | // Sort by complexity, this groups all similar expression types together. | |||
| 2987 | GroupByComplexity(Ops, &LI, DT); | |||
| 2988 | ||||
| 2989 | // If there are any constants, fold them together. | |||
| 2990 | unsigned Idx = 0; | |||
| 2991 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) { | |||
| 2992 | ++Idx; | |||
| 2993 | assert(Idx < Ops.size())((void)0); | |||
| 2994 | while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) { | |||
| 2995 | // We found two constants, fold them together! | |||
| 2996 | Ops[0] = getConstant(LHSC->getAPInt() * RHSC->getAPInt()); | |||
| 2997 | if (Ops.size() == 2) return Ops[0]; | |||
| 2998 | Ops.erase(Ops.begin()+1); // Erase the folded element | |||
| 2999 | LHSC = cast<SCEVConstant>(Ops[0]); | |||
| 3000 | } | |||
| 3001 | ||||
| 3002 | // If we have a multiply of zero, it will always be zero. | |||
| 3003 | if (LHSC->getValue()->isZero()) | |||
| 3004 | return LHSC; | |||
| 3005 | ||||
| 3006 | // If we are left with a constant one being multiplied, strip it off. | |||
| 3007 | if (LHSC->getValue()->isOne()) { | |||
| 3008 | Ops.erase(Ops.begin()); | |||
| 3009 | --Idx; | |||
| 3010 | } | |||
| 3011 | ||||
| 3012 | if (Ops.size() == 1) | |||
| 3013 | return Ops[0]; | |||
| 3014 | } | |||
| 3015 | ||||
| 3016 | // Delay expensive flag strengthening until necessary. | |||
| 3017 | auto ComputeFlags = [this, OrigFlags](const ArrayRef<const SCEV *> Ops) { | |||
| 3018 | return StrengthenNoWrapFlags(this, scMulExpr, Ops, OrigFlags); | |||
| 3019 | }; | |||
| 3020 | ||||
| 3021 | // Limit recursion calls depth. | |||
| 3022 | if (Depth > MaxArithDepth || hasHugeExpression(Ops)) | |||
| 3023 | return getOrCreateMulExpr(Ops, ComputeFlags(Ops)); | |||
| 3024 | ||||
| 3025 | if (SCEV *S = std::get<0>(findExistingSCEVInCache(scMulExpr, Ops))) { | |||
| 3026 | // Don't strengthen flags if we have no new information. | |||
| 3027 | SCEVMulExpr *Mul = static_cast<SCEVMulExpr *>(S); | |||
| 3028 | if (Mul->getNoWrapFlags(OrigFlags) != OrigFlags) | |||
| 3029 | Mul->setNoWrapFlags(ComputeFlags(Ops)); | |||
| 3030 | return S; | |||
| 3031 | } | |||
| 3032 | ||||
| 3033 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) { | |||
| 3034 | if (Ops.size() == 2) { | |||
| 3035 | // C1*(C2+V) -> C1*C2 + C1*V | |||
| 3036 | if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) | |||
| 3037 | // If any of Add's ops are Adds or Muls with a constant, apply this | |||
| 3038 | // transformation as well. | |||
| 3039 | // | |||
| 3040 | // TODO: There are some cases where this transformation is not | |||
| 3041 | // profitable; for example, Add = (C0 + X) * Y + Z. Maybe the scope of | |||
| 3042 | // this transformation should be narrowed down. | |||
| 3043 | if (Add->getNumOperands() == 2 && containsConstantInAddMulChain(Add)) | |||
| 3044 | return getAddExpr(getMulExpr(LHSC, Add->getOperand(0), | |||
| 3045 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 3046 | getMulExpr(LHSC, Add->getOperand(1), | |||
| 3047 | SCEV::FlagAnyWrap, Depth + 1), | |||
| 3048 | SCEV::FlagAnyWrap, Depth + 1); | |||
| 3049 | ||||
| 3050 | if (Ops[0]->isAllOnesValue()) { | |||
| 3051 | // If we have a mul by -1 of an add, try distributing the -1 among the | |||
| 3052 | // add operands. | |||
| 3053 | if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) { | |||
| 3054 | SmallVector<const SCEV *, 4> NewOps; | |||
| 3055 | bool AnyFolded = false; | |||
| 3056 | for (const SCEV *AddOp : Add->operands()) { | |||
| 3057 | const SCEV *Mul = getMulExpr(Ops[0], AddOp, SCEV::FlagAnyWrap, | |||
| 3058 | Depth + 1); | |||
| 3059 | if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true; | |||
| 3060 | NewOps.push_back(Mul); | |||
| 3061 | } | |||
| 3062 | if (AnyFolded) | |||
| 3063 | return getAddExpr(NewOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 3064 | } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) { | |||
| 3065 | // Negation preserves a recurrence's no self-wrap property. | |||
| 3066 | SmallVector<const SCEV *, 4> Operands; | |||
| 3067 | for (const SCEV *AddRecOp : AddRec->operands()) | |||
| 3068 | Operands.push_back(getMulExpr(Ops[0], AddRecOp, SCEV::FlagAnyWrap, | |||
| 3069 | Depth + 1)); | |||
| 3070 | ||||
| 3071 | return getAddRecExpr(Operands, AddRec->getLoop(), | |||
| 3072 | AddRec->getNoWrapFlags(SCEV::FlagNW)); | |||
| 3073 | } | |||
| 3074 | } | |||
| 3075 | } | |||
| 3076 | } | |||
| 3077 | ||||
| 3078 | // Skip over the add expression until we get to a multiply. | |||
| 3079 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr) | |||
| 3080 | ++Idx; | |||
| 3081 | ||||
| 3082 | // If there are mul operands inline them all into this expression. | |||
| 3083 | if (Idx < Ops.size()) { | |||
| 3084 | bool DeletedMul = false; | |||
| 3085 | while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) { | |||
| 3086 | if (Ops.size() > MulOpsInlineThreshold) | |||
| 3087 | break; | |||
| 3088 | // If we have an mul, expand the mul operands onto the end of the | |||
| 3089 | // operands list. | |||
| 3090 | Ops.erase(Ops.begin()+Idx); | |||
| 3091 | Ops.append(Mul->op_begin(), Mul->op_end()); | |||
| 3092 | DeletedMul = true; | |||
| 3093 | } | |||
| 3094 | ||||
| 3095 | // If we deleted at least one mul, we added operands to the end of the | |||
| 3096 | // list, and they are not necessarily sorted. Recurse to resort and | |||
| 3097 | // resimplify any operands we just acquired. | |||
| 3098 | if (DeletedMul) | |||
| 3099 | return getMulExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 3100 | } | |||
| 3101 | ||||
| 3102 | // If there are any add recurrences in the operands list, see if any other | |||
| 3103 | // added values are loop invariant. If so, we can fold them into the | |||
| 3104 | // recurrence. | |||
| 3105 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr) | |||
| 3106 | ++Idx; | |||
| 3107 | ||||
| 3108 | // Scan over all recurrences, trying to fold loop invariants into them. | |||
| 3109 | for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) { | |||
| 3110 | // Scan all of the other operands to this mul and add them to the vector | |||
| 3111 | // if they are loop invariant w.r.t. the recurrence. | |||
| 3112 | SmallVector<const SCEV *, 8> LIOps; | |||
| 3113 | const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]); | |||
| 3114 | const Loop *AddRecLoop = AddRec->getLoop(); | |||
| 3115 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) | |||
| 3116 | if (isAvailableAtLoopEntry(Ops[i], AddRecLoop)) { | |||
| 3117 | LIOps.push_back(Ops[i]); | |||
| 3118 | Ops.erase(Ops.begin()+i); | |||
| 3119 | --i; --e; | |||
| 3120 | } | |||
| 3121 | ||||
| 3122 | // If we found some loop invariants, fold them into the recurrence. | |||
| 3123 | if (!LIOps.empty()) { | |||
| 3124 | // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step} | |||
| 3125 | SmallVector<const SCEV *, 4> NewOps; | |||
| 3126 | NewOps.reserve(AddRec->getNumOperands()); | |||
| 3127 | const SCEV *Scale = getMulExpr(LIOps, SCEV::FlagAnyWrap, Depth + 1); | |||
| 3128 | for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) | |||
| 3129 | NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i), | |||
| 3130 | SCEV::FlagAnyWrap, Depth + 1)); | |||
| 3131 | ||||
| 3132 | // Build the new addrec. Propagate the NUW and NSW flags if both the | |||
| 3133 | // outer mul and the inner addrec are guaranteed to have no overflow. | |||
| 3134 | // | |||
| 3135 | // No self-wrap cannot be guaranteed after changing the step size, but | |||
| 3136 | // will be inferred if either NUW or NSW is true. | |||
| 3137 | SCEV::NoWrapFlags Flags = ComputeFlags({Scale, AddRec}); | |||
| 3138 | const SCEV *NewRec = getAddRecExpr( | |||
| 3139 | NewOps, AddRecLoop, AddRec->getNoWrapFlags(Flags)); | |||
| 3140 | ||||
| 3141 | // If all of the other operands were loop invariant, we are done. | |||
| 3142 | if (Ops.size() == 1) return NewRec; | |||
| 3143 | ||||
| 3144 | // Otherwise, multiply the folded AddRec by the non-invariant parts. | |||
| 3145 | for (unsigned i = 0;; ++i) | |||
| 3146 | if (Ops[i] == AddRec) { | |||
| 3147 | Ops[i] = NewRec; | |||
| 3148 | break; | |||
| 3149 | } | |||
| 3150 | return getMulExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 3151 | } | |||
| 3152 | ||||
| 3153 | // Okay, if there weren't any loop invariants to be folded, check to see | |||
| 3154 | // if there are multiple AddRec's with the same loop induction variable | |||
| 3155 | // being multiplied together. If so, we can fold them. | |||
| 3156 | ||||
| 3157 | // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L> | |||
| 3158 | // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [ | |||
| 3159 | // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z | |||
| 3160 | // ]]],+,...up to x=2n}. | |||
| 3161 | // Note that the arguments to choose() are always integers with values | |||
| 3162 | // known at compile time, never SCEV objects. | |||
| 3163 | // | |||
| 3164 | // The implementation avoids pointless extra computations when the two | |||
| 3165 | // addrec's are of different length (mathematically, it's equivalent to | |||
| 3166 | // an infinite stream of zeros on the right). | |||
| 3167 | bool OpsModified = false; | |||
| 3168 | for (unsigned OtherIdx = Idx+1; | |||
| 3169 | OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]); | |||
| 3170 | ++OtherIdx) { | |||
| 3171 | const SCEVAddRecExpr *OtherAddRec = | |||
| 3172 | dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]); | |||
| 3173 | if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop) | |||
| 3174 | continue; | |||
| 3175 | ||||
| 3176 | // Limit max number of arguments to avoid creation of unreasonably big | |||
| 3177 | // SCEVAddRecs with very complex operands. | |||
| 3178 | if (AddRec->getNumOperands() + OtherAddRec->getNumOperands() - 1 > | |||
| 3179 | MaxAddRecSize || hasHugeExpression({AddRec, OtherAddRec})) | |||
| 3180 | continue; | |||
| 3181 | ||||
| 3182 | bool Overflow = false; | |||
| 3183 | Type *Ty = AddRec->getType(); | |||
| 3184 | bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64; | |||
| 3185 | SmallVector<const SCEV*, 7> AddRecOps; | |||
| 3186 | for (int x = 0, xe = AddRec->getNumOperands() + | |||
| 3187 | OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) { | |||
| 3188 | SmallVector <const SCEV *, 7> SumOps; | |||
| 3189 | for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) { | |||
| 3190 | uint64_t Coeff1 = Choose(x, 2*x - y, Overflow); | |||
| 3191 | for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1), | |||
| 3192 | ze = std::min(x+1, (int)OtherAddRec->getNumOperands()); | |||
| 3193 | z < ze && !Overflow; ++z) { | |||
| 3194 | uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow); | |||
| 3195 | uint64_t Coeff; | |||
| 3196 | if (LargerThan64Bits) | |||
| 3197 | Coeff = umul_ov(Coeff1, Coeff2, Overflow); | |||
| 3198 | else | |||
| 3199 | Coeff = Coeff1*Coeff2; | |||
| 3200 | const SCEV *CoeffTerm = getConstant(Ty, Coeff); | |||
| 3201 | const SCEV *Term1 = AddRec->getOperand(y-z); | |||
| 3202 | const SCEV *Term2 = OtherAddRec->getOperand(z); | |||
| 3203 | SumOps.push_back(getMulExpr(CoeffTerm, Term1, Term2, | |||
| 3204 | SCEV::FlagAnyWrap, Depth + 1)); | |||
| 3205 | } | |||
| 3206 | } | |||
| 3207 | if (SumOps.empty()) | |||
| 3208 | SumOps.push_back(getZero(Ty)); | |||
| 3209 | AddRecOps.push_back(getAddExpr(SumOps, SCEV::FlagAnyWrap, Depth + 1)); | |||
| 3210 | } | |||
| 3211 | if (!Overflow) { | |||
| 3212 | const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRecLoop, | |||
| 3213 | SCEV::FlagAnyWrap); | |||
| 3214 | if (Ops.size() == 2) return NewAddRec; | |||
| 3215 | Ops[Idx] = NewAddRec; | |||
| 3216 | Ops.erase(Ops.begin() + OtherIdx); --OtherIdx; | |||
| 3217 | OpsModified = true; | |||
| 3218 | AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec); | |||
| 3219 | if (!AddRec) | |||
| 3220 | break; | |||
| 3221 | } | |||
| 3222 | } | |||
| 3223 | if (OpsModified) | |||
| 3224 | return getMulExpr(Ops, SCEV::FlagAnyWrap, Depth + 1); | |||
| 3225 | ||||
| 3226 | // Otherwise couldn't fold anything into this recurrence. Move onto the | |||
| 3227 | // next one. | |||
| 3228 | } | |||
| 3229 | ||||
| 3230 | // Okay, it looks like we really DO need an mul expr. Check to see if we | |||
| 3231 | // already have one, otherwise create a new one. | |||
| 3232 | return getOrCreateMulExpr(Ops, ComputeFlags(Ops)); | |||
| 3233 | } | |||
| 3234 | ||||
| 3235 | /// Represents an unsigned remainder expression based on unsigned division. | |||
| 3236 | const SCEV *ScalarEvolution::getURemExpr(const SCEV *LHS, | |||
| 3237 | const SCEV *RHS) { | |||
| 3238 | assert(getEffectiveSCEVType(LHS->getType()) ==((void)0) | |||
| 3239 | getEffectiveSCEVType(RHS->getType()) &&((void)0) | |||
| 3240 | "SCEVURemExpr operand types don't match!")((void)0); | |||
| 3241 | ||||
| 3242 | // Short-circuit easy cases | |||
| 3243 | if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) { | |||
| 3244 | // If constant is one, the result is trivial | |||
| 3245 | if (RHSC->getValue()->isOne()) | |||
| 3246 | return getZero(LHS->getType()); // X urem 1 --> 0 | |||
| 3247 | ||||
| 3248 | // If constant is a power of two, fold into a zext(trunc(LHS)). | |||
| 3249 | if (RHSC->getAPInt().isPowerOf2()) { | |||
| 3250 | Type *FullTy = LHS->getType(); | |||
| 3251 | Type *TruncTy = | |||
| 3252 | IntegerType::get(getContext(), RHSC->getAPInt().logBase2()); | |||
| 3253 | return getZeroExtendExpr(getTruncateExpr(LHS, TruncTy), FullTy); | |||
| 3254 | } | |||
| 3255 | } | |||
| 3256 | ||||
| 3257 | // Fallback to %a == %x urem %y == %x -<nuw> ((%x udiv %y) *<nuw> %y) | |||
| 3258 | const SCEV *UDiv = getUDivExpr(LHS, RHS); | |||
| 3259 | const SCEV *Mult = getMulExpr(UDiv, RHS, SCEV::FlagNUW); | |||
| 3260 | return getMinusSCEV(LHS, Mult, SCEV::FlagNUW); | |||
| 3261 | } | |||
| 3262 | ||||
| 3263 | /// Get a canonical unsigned division expression, or something simpler if | |||
| 3264 | /// possible. | |||
| 3265 | const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS, | |||
| 3266 | const SCEV *RHS) { | |||
| 3267 | assert(!LHS->getType()->isPointerTy() &&((void)0) | |||
| 3268 | "SCEVUDivExpr operand can't be pointer!")((void)0); | |||
| 3269 | assert(LHS->getType() == RHS->getType() &&((void)0) | |||
| 3270 | "SCEVUDivExpr operand types don't match!")((void)0); | |||
| 3271 | ||||
| 3272 | FoldingSetNodeID ID; | |||
| 3273 | ID.AddInteger(scUDivExpr); | |||
| 3274 | ID.AddPointer(LHS); | |||
| 3275 | ID.AddPointer(RHS); | |||
| 3276 | void *IP = nullptr; | |||
| 3277 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) | |||
| 3278 | return S; | |||
| 3279 | ||||
| 3280 | // 0 udiv Y == 0 | |||
| 3281 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) | |||
| 3282 | if (LHSC->getValue()->isZero()) | |||
| 3283 | return LHS; | |||
| 3284 | ||||
| 3285 | if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) { | |||
| 3286 | if (RHSC->getValue()->isOne()) | |||
| 3287 | return LHS; // X udiv 1 --> x | |||
| 3288 | // If the denominator is zero, the result of the udiv is undefined. Don't | |||
| 3289 | // try to analyze it, because the resolution chosen here may differ from | |||
| 3290 | // the resolution chosen in other parts of the compiler. | |||
| 3291 | if (!RHSC->getValue()->isZero()) { | |||
| 3292 | // Determine if the division can be folded into the operands of | |||
| 3293 | // its operands. | |||
| 3294 | // TODO: Generalize this to non-constants by using known-bits information. | |||
| 3295 | Type *Ty = LHS->getType(); | |||
| 3296 | unsigned LZ = RHSC->getAPInt().countLeadingZeros(); | |||
| 3297 | unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1; | |||
| 3298 | // For non-power-of-two values, effectively round the value up to the | |||
| 3299 | // nearest power of two. | |||
| 3300 | if (!RHSC->getAPInt().isPowerOf2()) | |||
| 3301 | ++MaxShiftAmt; | |||
| 3302 | IntegerType *ExtTy = | |||
| 3303 | IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt); | |||
| 3304 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) | |||
| 3305 | if (const SCEVConstant *Step = | |||
| 3306 | dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) { | |||
| 3307 | // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded. | |||
| 3308 | const APInt &StepInt = Step->getAPInt(); | |||
| 3309 | const APInt &DivInt = RHSC->getAPInt(); | |||
| 3310 | if (!StepInt.urem(DivInt) && | |||
| 3311 | getZeroExtendExpr(AR, ExtTy) == | |||
| 3312 | getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy), | |||
| 3313 | getZeroExtendExpr(Step, ExtTy), | |||
| 3314 | AR->getLoop(), SCEV::FlagAnyWrap)) { | |||
| 3315 | SmallVector<const SCEV *, 4> Operands; | |||
| 3316 | for (const SCEV *Op : AR->operands()) | |||
| 3317 | Operands.push_back(getUDivExpr(Op, RHS)); | |||
| 3318 | return getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagNW); | |||
| 3319 | } | |||
| 3320 | /// Get a canonical UDivExpr for a recurrence. | |||
| 3321 | /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0. | |||
| 3322 | // We can currently only fold X%N if X is constant. | |||
| 3323 | const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart()); | |||
| 3324 | if (StartC && !DivInt.urem(StepInt) && | |||
| 3325 | getZeroExtendExpr(AR, ExtTy) == | |||
| 3326 | getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy), | |||
| 3327 | getZeroExtendExpr(Step, ExtTy), | |||
| 3328 | AR->getLoop(), SCEV::FlagAnyWrap)) { | |||
| 3329 | const APInt &StartInt = StartC->getAPInt(); | |||
| 3330 | const APInt &StartRem = StartInt.urem(StepInt); | |||
| 3331 | if (StartRem != 0) { | |||
| 3332 | const SCEV *NewLHS = | |||
| 3333 | getAddRecExpr(getConstant(StartInt - StartRem), Step, | |||
| 3334 | AR->getLoop(), SCEV::FlagNW); | |||
| 3335 | if (LHS != NewLHS) { | |||
| 3336 | LHS = NewLHS; | |||
| 3337 | ||||
| 3338 | // Reset the ID to include the new LHS, and check if it is | |||
| 3339 | // already cached. | |||
| 3340 | ID.clear(); | |||
| 3341 | ID.AddInteger(scUDivExpr); | |||
| 3342 | ID.AddPointer(LHS); | |||
| 3343 | ID.AddPointer(RHS); | |||
| 3344 | IP = nullptr; | |||
| 3345 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) | |||
| 3346 | return S; | |||
| 3347 | } | |||
| 3348 | } | |||
| 3349 | } | |||
| 3350 | } | |||
| 3351 | // (A*B)/C --> A*(B/C) if safe and B/C can be folded. | |||
| 3352 | if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) { | |||
| 3353 | SmallVector<const SCEV *, 4> Operands; | |||
| 3354 | for (const SCEV *Op : M->operands()) | |||
| 3355 | Operands.push_back(getZeroExtendExpr(Op, ExtTy)); | |||
| 3356 | if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands)) | |||
| 3357 | // Find an operand that's safely divisible. | |||
| 3358 | for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) { | |||
| 3359 | const SCEV *Op = M->getOperand(i); | |||
| 3360 | const SCEV *Div = getUDivExpr(Op, RHSC); | |||
| 3361 | if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) { | |||
| 3362 | Operands = SmallVector<const SCEV *, 4>(M->operands()); | |||
| 3363 | Operands[i] = Div; | |||
| 3364 | return getMulExpr(Operands); | |||
| 3365 | } | |||
| 3366 | } | |||
| 3367 | } | |||
| 3368 | ||||
| 3369 | // (A/B)/C --> A/(B*C) if safe and B*C can be folded. | |||
| 3370 | if (const SCEVUDivExpr *OtherDiv = dyn_cast<SCEVUDivExpr>(LHS)) { | |||
| 3371 | if (auto *DivisorConstant = | |||
| 3372 | dyn_cast<SCEVConstant>(OtherDiv->getRHS())) { | |||
| 3373 | bool Overflow = false; | |||
| 3374 | APInt NewRHS = | |||
| 3375 | DivisorConstant->getAPInt().umul_ov(RHSC->getAPInt(), Overflow); | |||
| 3376 | if (Overflow) { | |||
| 3377 | return getConstant(RHSC->getType(), 0, false); | |||
| 3378 | } | |||
| 3379 | return getUDivExpr(OtherDiv->getLHS(), getConstant(NewRHS)); | |||
| 3380 | } | |||
| 3381 | } | |||
| 3382 | ||||
| 3383 | // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded. | |||
| 3384 | if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) { | |||
| 3385 | SmallVector<const SCEV *, 4> Operands; | |||
| 3386 | for (const SCEV *Op : A->operands()) | |||
| 3387 | Operands.push_back(getZeroExtendExpr(Op, ExtTy)); | |||
| 3388 | if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) { | |||
| 3389 | Operands.clear(); | |||
| 3390 | for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) { | |||
| 3391 | const SCEV *Op = getUDivExpr(A->getOperand(i), RHS); | |||
| 3392 | if (isa<SCEVUDivExpr>(Op) || | |||
| 3393 | getMulExpr(Op, RHS) != A->getOperand(i)) | |||
| 3394 | break; | |||
| 3395 | Operands.push_back(Op); | |||
| 3396 | } | |||
| 3397 | if (Operands.size() == A->getNumOperands()) | |||
| 3398 | return getAddExpr(Operands); | |||
| 3399 | } | |||
| 3400 | } | |||
| 3401 | ||||
| 3402 | // Fold if both operands are constant. | |||
| 3403 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) { | |||
| 3404 | Constant *LHSCV = LHSC->getValue(); | |||
| 3405 | Constant *RHSCV = RHSC->getValue(); | |||
| 3406 | return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV, | |||
| 3407 | RHSCV))); | |||
| 3408 | } | |||
| 3409 | } | |||
| 3410 | } | |||
| 3411 | ||||
| 3412 | // The Insertion Point (IP) might be invalid by now (due to UniqueSCEVs | |||
| 3413 | // changes). Make sure we get a new one. | |||
| 3414 | IP = nullptr; | |||
| 3415 | if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S; | |||
| 3416 | SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator), | |||
| 3417 | LHS, RHS); | |||
| 3418 | UniqueSCEVs.InsertNode(S, IP); | |||
| 3419 | addToLoopUseLists(S); | |||
| 3420 | return S; | |||
| 3421 | } | |||
| 3422 | ||||
| 3423 | static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) { | |||
| 3424 | APInt A = C1->getAPInt().abs(); | |||
| 3425 | APInt B = C2->getAPInt().abs(); | |||
| 3426 | uint32_t ABW = A.getBitWidth(); | |||
| 3427 | uint32_t BBW = B.getBitWidth(); | |||
| 3428 | ||||
| 3429 | if (ABW > BBW) | |||
| 3430 | B = B.zext(ABW); | |||
| 3431 | else if (ABW < BBW) | |||
| 3432 | A = A.zext(BBW); | |||
| 3433 | ||||
| 3434 | return APIntOps::GreatestCommonDivisor(std::move(A), std::move(B)); | |||
| 3435 | } | |||
| 3436 | ||||
| 3437 | /// Get a canonical unsigned division expression, or something simpler if | |||
| 3438 | /// possible. There is no representation for an exact udiv in SCEV IR, but we | |||
| 3439 | /// can attempt to remove factors from the LHS and RHS. We can't do this when | |||
| 3440 | /// it's not exact because the udiv may be clearing bits. | |||
| 3441 | const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS, | |||
| 3442 | const SCEV *RHS) { | |||
| 3443 | // TODO: we could try to find factors in all sorts of things, but for now we | |||
| 3444 | // just deal with u/exact (multiply, constant). See SCEVDivision towards the | |||
| 3445 | // end of this file for inspiration. | |||
| 3446 | ||||
| 3447 | const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS); | |||
| 3448 | if (!Mul || !Mul->hasNoUnsignedWrap()) | |||
| 3449 | return getUDivExpr(LHS, RHS); | |||
| 3450 | ||||
| 3451 | if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) { | |||
| 3452 | // If the mulexpr multiplies by a constant, then that constant must be the | |||
| 3453 | // first element of the mulexpr. | |||
| 3454 | if (const auto *LHSCst = dyn_cast<SCEVConstant>(Mul->getOperand(0))) { | |||
| 3455 | if (LHSCst == RHSCst) { | |||
| 3456 | SmallVector<const SCEV *, 2> Operands(drop_begin(Mul->operands())); | |||
| 3457 | return getMulExpr(Operands); | |||
| 3458 | } | |||
| 3459 | ||||
| 3460 | // We can't just assume that LHSCst divides RHSCst cleanly, it could be | |||
| 3461 | // that there's a factor provided by one of the other terms. We need to | |||
| 3462 | // check. | |||
| 3463 | APInt Factor = gcd(LHSCst, RHSCst); | |||
| 3464 | if (!Factor.isIntN(1)) { | |||
| 3465 | LHSCst = | |||
| 3466 | cast<SCEVConstant>(getConstant(LHSCst->getAPInt().udiv(Factor))); | |||
| 3467 | RHSCst = | |||
| 3468 | cast<SCEVConstant>(getConstant(RHSCst->getAPInt().udiv(Factor))); | |||
| 3469 | SmallVector<const SCEV *, 2> Operands; | |||
| 3470 | Operands.push_back(LHSCst); | |||
| 3471 | Operands.append(Mul->op_begin() + 1, Mul->op_end()); | |||
| 3472 | LHS = getMulExpr(Operands); | |||
| 3473 | RHS = RHSCst; | |||
| 3474 | Mul = dyn_cast<SCEVMulExpr>(LHS); | |||
| 3475 | if (!Mul) | |||
| 3476 | return getUDivExactExpr(LHS, RHS); | |||
| 3477 | } | |||
| 3478 | } | |||
| 3479 | } | |||
| 3480 | ||||
| 3481 | for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) { | |||
| 3482 | if (Mul->getOperand(i) == RHS) { | |||
| 3483 | SmallVector<const SCEV *, 2> Operands; | |||
| 3484 | Operands.append(Mul->op_begin(), Mul->op_begin() + i); | |||
| 3485 | Operands.append(Mul->op_begin() + i + 1, Mul->op_end()); | |||
| 3486 | return getMulExpr(Operands); | |||
| 3487 | } | |||
| 3488 | } | |||
| 3489 | ||||
| 3490 | return getUDivExpr(LHS, RHS); | |||
| 3491 | } | |||
| 3492 | ||||
| 3493 | /// Get an add recurrence expression for the specified loop. Simplify the | |||
| 3494 | /// expression as much as possible. | |||
| 3495 | const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step, | |||
| 3496 | const Loop *L, | |||
| 3497 | SCEV::NoWrapFlags Flags) { | |||
| 3498 | SmallVector<const SCEV *, 4> Operands; | |||
| 3499 | Operands.push_back(Start); | |||
| 3500 | if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step)) | |||
| 3501 | if (StepChrec->getLoop() == L) { | |||
| 3502 | Operands.append(StepChrec->op_begin(), StepChrec->op_end()); | |||
| 3503 | return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW)); | |||
| 3504 | } | |||
| 3505 | ||||
| 3506 | Operands.push_back(Step); | |||
| 3507 | return getAddRecExpr(Operands, L, Flags); | |||
| 3508 | } | |||
| 3509 | ||||
| 3510 | /// Get an add recurrence expression for the specified loop. Simplify the | |||
| 3511 | /// expression as much as possible. | |||
| 3512 | const SCEV * | |||
| 3513 | ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, | |||
| 3514 | const Loop *L, SCEV::NoWrapFlags Flags) { | |||
| 3515 | if (Operands.size() == 1) return Operands[0]; | |||
| 3516 | #ifndef NDEBUG1 | |||
| 3517 | Type *ETy = getEffectiveSCEVType(Operands[0]->getType()); | |||
| 3518 | for (unsigned i = 1, e = Operands.size(); i != e; ++i) { | |||
| 3519 | assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&((void)0) | |||
| 3520 | "SCEVAddRecExpr operand types don't match!")((void)0); | |||
| 3521 | assert(!Operands[i]->getType()->isPointerTy() && "Step must be integer")((void)0); | |||
| 3522 | } | |||
| 3523 | for (unsigned i = 0, e = Operands.size(); i != e; ++i) | |||
| 3524 | assert(isLoopInvariant(Operands[i], L) &&((void)0) | |||
| 3525 | "SCEVAddRecExpr operand is not loop-invariant!")((void)0); | |||
| 3526 | #endif | |||
| 3527 | ||||
| 3528 | if (Operands.back()->isZero()) { | |||
| 3529 | Operands.pop_back(); | |||
| 3530 | return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X | |||
| 3531 | } | |||
| 3532 | ||||
| 3533 | // It's tempting to want to call getConstantMaxBackedgeTakenCount count here and | |||
| 3534 | // use that information to infer NUW and NSW flags. However, computing a | |||
| 3535 | // BE count requires calling getAddRecExpr, so we may not yet have a | |||
| 3536 | // meaningful BE count at this point (and if we don't, we'd be stuck | |||
| 3537 | // with a SCEVCouldNotCompute as the cached BE count). | |||
| 3538 | ||||
| 3539 | Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags); | |||
| 3540 | ||||
| 3541 | // Canonicalize nested AddRecs in by nesting them in order of loop depth. | |||
| 3542 | if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) { | |||
| 3543 | const Loop *NestedLoop = NestedAR->getLoop(); | |||
| 3544 | if (L->contains(NestedLoop) | |||
| 3545 | ? (L->getLoopDepth() < NestedLoop->getLoopDepth()) | |||
| 3546 | : (!NestedLoop->contains(L) && | |||
| 3547 | DT.dominates(L->getHeader(), NestedLoop->getHeader()))) { | |||
| 3548 | SmallVector<const SCEV *, 4> NestedOperands(NestedAR->operands()); | |||
| 3549 | Operands[0] = NestedAR->getStart(); | |||
| 3550 | // AddRecs require their operands be loop-invariant with respect to their | |||
| 3551 | // loops. Don't perform this transformation if it would break this | |||
| 3552 | // requirement. | |||
| 3553 | bool AllInvariant = all_of( | |||
| 3554 | Operands, [&](const SCEV *Op) { return isLoopInvariant(Op, L); }); | |||
| 3555 | ||||
| 3556 | if (AllInvariant) { | |||
| 3557 | // Create a recurrence for the outer loop with the same step size. | |||
| 3558 | // | |||
| 3559 | // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the | |||
| 3560 | // inner recurrence has the same property. | |||
| 3561 | SCEV::NoWrapFlags OuterFlags = | |||
| 3562 | maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags()); | |||
| 3563 | ||||
| 3564 | NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags); | |||
| 3565 | AllInvariant = all_of(NestedOperands, [&](const SCEV *Op) { | |||
| 3566 | return isLoopInvariant(Op, NestedLoop); | |||
| 3567 | }); | |||
| 3568 | ||||
| 3569 | if (AllInvariant) { | |||
| 3570 | // Ok, both add recurrences are valid after the transformation. | |||
| 3571 | // | |||
| 3572 | // The inner recurrence keeps its NW flag but only keeps NUW/NSW if | |||
| 3573 | // the outer recurrence has the same property. | |||
| 3574 | SCEV::NoWrapFlags InnerFlags = | |||
| 3575 | maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags); | |||
| 3576 | return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags); | |||
| 3577 | } | |||
| 3578 | } | |||
| 3579 | // Reset Operands to its original state. | |||
| 3580 | Operands[0] = NestedAR; | |||
| 3581 | } | |||
| 3582 | } | |||
| 3583 | ||||
| 3584 | // Okay, it looks like we really DO need an addrec expr. Check to see if we | |||
| 3585 | // already have one, otherwise create a new one. | |||
| 3586 | return getOrCreateAddRecExpr(Operands, L, Flags); | |||
| 3587 | } | |||
| 3588 | ||||
| 3589 | const SCEV * | |||
| 3590 | ScalarEvolution::getGEPExpr(GEPOperator *GEP, | |||
| 3591 | const SmallVectorImpl<const SCEV *> &IndexExprs) { | |||
| 3592 | const SCEV *BaseExpr = getSCEV(GEP->getPointerOperand()); | |||
| 3593 | // getSCEV(Base)->getType() has the same address space as Base->getType() | |||
| 3594 | // because SCEV::getType() preserves the address space. | |||
| 3595 | Type *IntIdxTy = getEffectiveSCEVType(BaseExpr->getType()); | |||
| 3596 | // FIXME(PR23527): Don't blindly transfer the inbounds flag from the GEP | |||
| 3597 | // instruction to its SCEV, because the Instruction may be guarded by control | |||
| 3598 | // flow and the no-overflow bits may not be valid for the expression in any | |||
| 3599 | // context. This can be fixed similarly to how these flags are handled for | |||
| 3600 | // adds. | |||
| 3601 | SCEV::NoWrapFlags OffsetWrap = | |||
| 3602 | GEP->isInBounds() ? SCEV::FlagNSW : SCEV::FlagAnyWrap; | |||
| 3603 | ||||
| 3604 | Type *CurTy = GEP->getType(); | |||
| 3605 | bool FirstIter = true; | |||
| 3606 | SmallVector<const SCEV *, 4> Offsets; | |||
| 3607 | for (const SCEV *IndexExpr : IndexExprs) { | |||
| 3608 | // Compute the (potentially symbolic) offset in bytes for this index. | |||
| 3609 | if (StructType *STy = dyn_cast<StructType>(CurTy)) { | |||
| 3610 | // For a struct, add the member offset. | |||
| 3611 | ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue(); | |||
| 3612 | unsigned FieldNo = Index->getZExtValue(); | |||
| 3613 | const SCEV *FieldOffset = getOffsetOfExpr(IntIdxTy, STy, FieldNo); | |||
| 3614 | Offsets.push_back(FieldOffset); | |||
| 3615 | ||||
| 3616 | // Update CurTy to the type of the field at Index. | |||
| 3617 | CurTy = STy->getTypeAtIndex(Index); | |||
| 3618 | } else { | |||
| 3619 | // Update CurTy to its element type. | |||
| 3620 | if (FirstIter) { | |||
| 3621 | assert(isa<PointerType>(CurTy) &&((void)0) | |||
| 3622 | "The first index of a GEP indexes a pointer")((void)0); | |||
| 3623 | CurTy = GEP->getSourceElementType(); | |||
| 3624 | FirstIter = false; | |||
| 3625 | } else { | |||
| 3626 | CurTy = GetElementPtrInst::getTypeAtIndex(CurTy, (uint64_t)0); | |||
| 3627 | } | |||
| 3628 | // For an array, add the element offset, explicitly scaled. | |||
| 3629 | const SCEV *ElementSize = getSizeOfExpr(IntIdxTy, CurTy); | |||
| 3630 | // Getelementptr indices are signed. | |||
| 3631 | IndexExpr = getTruncateOrSignExtend(IndexExpr, IntIdxTy); | |||
| 3632 | ||||
| 3633 | // Multiply the index by the element size to compute the element offset. | |||
| 3634 | const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, OffsetWrap); | |||
| 3635 | Offsets.push_back(LocalOffset); | |||
| 3636 | } | |||
| 3637 | } | |||
| 3638 | ||||
| 3639 | // Handle degenerate case of GEP without offsets. | |||
| 3640 | if (Offsets.empty()) | |||
| 3641 | return BaseExpr; | |||
| 3642 | ||||
| 3643 | // Add the offsets together, assuming nsw if inbounds. | |||
| 3644 | const SCEV *Offset = getAddExpr(Offsets, OffsetWrap); | |||
| 3645 | // Add the base address and the offset. We cannot use the nsw flag, as the | |||
| 3646 | // base address is unsigned. However, if we know that the offset is | |||
| 3647 | // non-negative, we can use nuw. | |||
| 3648 | SCEV::NoWrapFlags BaseWrap = GEP->isInBounds() && isKnownNonNegative(Offset) | |||
| 3649 | ? SCEV::FlagNUW : SCEV::FlagAnyWrap; | |||
| 3650 | return getAddExpr(BaseExpr, Offset, BaseWrap); | |||
| 3651 | } | |||
| 3652 | ||||
| 3653 | std::tuple<SCEV *, FoldingSetNodeID, void *> | |||
| 3654 | ScalarEvolution::findExistingSCEVInCache(SCEVTypes SCEVType, | |||
| 3655 | ArrayRef<const SCEV *> Ops) { | |||
| 3656 | FoldingSetNodeID ID; | |||
| 3657 | void *IP = nullptr; | |||
| 3658 | ID.AddInteger(SCEVType); | |||
| 3659 | for (unsigned i = 0, e = Ops.size(); i != e; ++i) | |||
| 3660 | ID.AddPointer(Ops[i]); | |||
| 3661 | return std::tuple<SCEV *, FoldingSetNodeID, void *>( | |||
| 3662 | UniqueSCEVs.FindNodeOrInsertPos(ID, IP), std::move(ID), IP); | |||
| 3663 | } | |||
| 3664 | ||||
| 3665 | const SCEV *ScalarEvolution::getAbsExpr(const SCEV *Op, bool IsNSW) { | |||
| 3666 | SCEV::NoWrapFlags Flags = IsNSW ? SCEV::FlagNSW : SCEV::FlagAnyWrap; | |||
| 3667 | return getSMaxExpr(Op, getNegativeSCEV(Op, Flags)); | |||
| 3668 | } | |||
| 3669 | ||||
| 3670 | const SCEV *ScalarEvolution::getMinMaxExpr(SCEVTypes Kind, | |||
| 3671 | SmallVectorImpl<const SCEV *> &Ops) { | |||
| 3672 | assert(!Ops.empty() && "Cannot get empty (u|s)(min|max)!")((void)0); | |||
| 3673 | if (Ops.size() == 1) return Ops[0]; | |||
| 3674 | #ifndef NDEBUG1 | |||
| 3675 | Type *ETy = getEffectiveSCEVType(Ops[0]->getType()); | |||
| 3676 | for (unsigned i = 1, e = Ops.size(); i != e; ++i) { | |||
| 3677 | assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((void)0) | |||
| 3678 | "Operand types don't match!")((void)0); | |||
| 3679 | assert(Ops[0]->getType()->isPointerTy() ==((void)0) | |||
| 3680 | Ops[i]->getType()->isPointerTy() &&((void)0) | |||
| 3681 | "min/max should be consistently pointerish")((void)0); | |||
| 3682 | } | |||
| 3683 | #endif | |||
| 3684 | ||||
| 3685 | bool IsSigned = Kind == scSMaxExpr || Kind == scSMinExpr; | |||
| 3686 | bool IsMax = Kind == scSMaxExpr || Kind == scUMaxExpr; | |||
| 3687 | ||||
| 3688 | // Sort by complexity, this groups all similar expression types together. | |||
| 3689 | GroupByComplexity(Ops, &LI, DT); | |||
| 3690 | ||||
| 3691 | // Check if we have created the same expression before. | |||
| 3692 | if (const SCEV *S = std::get<0>(findExistingSCEVInCache(Kind, Ops))) { | |||
| 3693 | return S; | |||
| 3694 | } | |||
| 3695 | ||||
| 3696 | // If there are any constants, fold them together. | |||
| 3697 | unsigned Idx = 0; | |||
| 3698 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) { | |||
| 3699 | ++Idx; | |||
| 3700 | assert(Idx < Ops.size())((void)0); | |||
| 3701 | auto FoldOp = [&](const APInt &LHS, const APInt &RHS) { | |||
| 3702 | if (Kind == scSMaxExpr) | |||
| 3703 | return APIntOps::smax(LHS, RHS); | |||
| 3704 | else if (Kind == scSMinExpr) | |||
| 3705 | return APIntOps::smin(LHS, RHS); | |||
| 3706 | else if (Kind == scUMaxExpr) | |||
| 3707 | return APIntOps::umax(LHS, RHS); | |||
| 3708 | else if (Kind == scUMinExpr) | |||
| 3709 | return APIntOps::umin(LHS, RHS); | |||
| 3710 | llvm_unreachable("Unknown SCEV min/max opcode")__builtin_unreachable(); | |||
| 3711 | }; | |||
| 3712 | ||||
| 3713 | while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) { | |||
| 3714 | // We found two constants, fold them together! | |||
| 3715 | ConstantInt *Fold = ConstantInt::get( | |||
| 3716 | getContext(), FoldOp(LHSC->getAPInt(), RHSC->getAPInt())); | |||
| 3717 | Ops[0] = getConstant(Fold); | |||
| 3718 | Ops.erase(Ops.begin()+1); // Erase the folded element | |||
| 3719 | if (Ops.size() == 1) return Ops[0]; | |||
| 3720 | LHSC = cast<SCEVConstant>(Ops[0]); | |||
| 3721 | } | |||
| 3722 | ||||
| 3723 | bool IsMinV = LHSC->getValue()->isMinValue(IsSigned); | |||
| 3724 | bool IsMaxV = LHSC->getValue()->isMaxValue(IsSigned); | |||
| 3725 | ||||
| 3726 | if (IsMax ? IsMinV : IsMaxV) { | |||
| 3727 | // If we are left with a constant minimum(/maximum)-int, strip it off. | |||
| 3728 | Ops.erase(Ops.begin()); | |||
| 3729 | --Idx; | |||
| 3730 | } else if (IsMax ? IsMaxV : IsMinV) { | |||
| 3731 | // If we have a max(/min) with a constant maximum(/minimum)-int, | |||
| 3732 | // it will always be the extremum. | |||
| 3733 | return LHSC; | |||
| 3734 | } | |||
| 3735 | ||||
| 3736 | if (Ops.size() == 1) return Ops[0]; | |||
| 3737 | } | |||
| 3738 | ||||
| 3739 | // Find the first operation of the same kind | |||
| 3740 | while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < Kind) | |||
| 3741 | ++Idx; | |||
| 3742 | ||||
| 3743 | // Check to see if one of the operands is of the same kind. If so, expand its | |||
| 3744 | // operands onto our operand list, and recurse to simplify. | |||
| 3745 | if (Idx < Ops.size()) { | |||
| 3746 | bool DeletedAny = false; | |||
| 3747 | while (Ops[Idx]->getSCEVType() == Kind) { | |||
| 3748 | const SCEVMinMaxExpr *SMME = cast<SCEVMinMaxExpr>(Ops[Idx]); | |||
| 3749 | Ops.erase(Ops.begin()+Idx); | |||
| 3750 | Ops.append(SMME->op_begin(), SMME->op_end()); | |||
| 3751 | DeletedAny = true; | |||
| 3752 | } | |||
| 3753 | ||||
| 3754 | if (DeletedAny) | |||
| 3755 | return getMinMaxExpr(Kind, Ops); | |||
| 3756 | } | |||
| 3757 | ||||
| 3758 | // Okay, check to see if the same value occurs in the operand list twice. If | |||
| 3759 | // so, delete one. Since we sorted the list, these values are required to | |||
| 3760 | // be adjacent. | |||
| 3761 | llvm::CmpInst::Predicate GEPred = | |||
| 3762 | IsSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; | |||
| 3763 | llvm::CmpInst::Predicate LEPred = | |||
| 3764 | IsSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; | |||
| 3765 | llvm::CmpInst::Predicate FirstPred = IsMax ? GEPred : LEPred; | |||
| 3766 | llvm::CmpInst::Predicate SecondPred = IsMax ? LEPred : GEPred; | |||
| 3767 | for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) { | |||
| 3768 | if (Ops[i] == Ops[i + 1] || | |||
| 3769 | isKnownViaNonRecursiveReasoning(FirstPred, Ops[i], Ops[i + 1])) { | |||
| 3770 | // X op Y op Y --> X op Y | |||
| 3771 | // X op Y --> X, if we know X, Y are ordered appropriately | |||
| 3772 | Ops.erase(Ops.begin() + i + 1, Ops.begin() + i + 2); | |||
| 3773 | --i; | |||
| 3774 | --e; | |||
| 3775 | } else if (isKnownViaNonRecursiveReasoning(SecondPred, Ops[i], | |||
| 3776 | Ops[i + 1])) { | |||
| 3777 | // X op Y --> Y, if we know X, Y are ordered appropriately | |||
| 3778 | Ops.erase(Ops.begin() + i, Ops.begin() + i + 1); | |||
| 3779 | --i; | |||
| 3780 | --e; | |||
| 3781 | } | |||
| 3782 | } | |||
| 3783 | ||||
| 3784 | if (Ops.size() == 1) return Ops[0]; | |||
| 3785 | ||||
| 3786 | assert(!Ops.empty() && "Reduced smax down to nothing!")((void)0); | |||
| 3787 | ||||
| 3788 | // Okay, it looks like we really DO need an expr. Check to see if we | |||
| 3789 | // already have one, otherwise create a new one. | |||
| 3790 | const SCEV *ExistingSCEV; | |||
| 3791 | FoldingSetNodeID ID; | |||
| 3792 | void *IP; | |||
| 3793 | std::tie(ExistingSCEV, ID, IP) = findExistingSCEVInCache(Kind, Ops); | |||
| 3794 | if (ExistingSCEV) | |||
| 3795 | return ExistingSCEV; | |||
| 3796 | const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size()); | |||
| 3797 | std::uninitialized_copy(Ops.begin(), Ops.end(), O); | |||
| 3798 | SCEV *S = new (SCEVAllocator) | |||
| 3799 | SCEVMinMaxExpr(ID.Intern(SCEVAllocator), Kind, O, Ops.size()); | |||
| 3800 | ||||
| 3801 | UniqueSCEVs.InsertNode(S, IP); | |||
| 3802 | addToLoopUseLists(S); | |||
| 3803 | return S; | |||
| 3804 | } | |||
| 3805 | ||||
| 3806 | const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS, const SCEV *RHS) { | |||
| 3807 | SmallVector<const SCEV *, 2> Ops = {LHS, RHS}; | |||
| 3808 | return getSMaxExpr(Ops); | |||
| 3809 | } | |||
| 3810 | ||||
| 3811 | const SCEV *ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) { | |||
| 3812 | return getMinMaxExpr(scSMaxExpr, Ops); | |||
| 3813 | } | |||
| 3814 | ||||
| 3815 | const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS, const SCEV *RHS) { | |||
| 3816 | SmallVector<const SCEV *, 2> Ops = {LHS, RHS}; | |||
| 3817 | return getUMaxExpr(Ops); | |||
| 3818 | } | |||
| 3819 | ||||
| 3820 | const SCEV *ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) { | |||
| 3821 | return getMinMaxExpr(scUMaxExpr, Ops); | |||
| 3822 | } | |||
| 3823 | ||||
| 3824 | const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS, | |||
| 3825 | const SCEV *RHS) { | |||
| 3826 | SmallVector<const SCEV *, 2> Ops = { LHS, RHS }; | |||
| 3827 | return getSMinExpr(Ops); | |||
| 3828 | } | |||
| 3829 | ||||
| 3830 | const SCEV *ScalarEvolution::getSMinExpr(SmallVectorImpl<const SCEV *> &Ops) { | |||
| 3831 | return getMinMaxExpr(scSMinExpr, Ops); | |||
| 3832 | } | |||
| 3833 | ||||
| 3834 | const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS, | |||
| 3835 | const SCEV *RHS) { | |||
| 3836 | SmallVector<const SCEV *, 2> Ops = { LHS, RHS }; | |||
| 3837 | return getUMinExpr(Ops); | |||
| 3838 | } | |||
| 3839 | ||||
| 3840 | const SCEV *ScalarEvolution::getUMinExpr(SmallVectorImpl<const SCEV *> &Ops) { | |||
| 3841 | return getMinMaxExpr(scUMinExpr, Ops); | |||
| 3842 | } | |||
| 3843 | ||||
| 3844 | const SCEV * | |||
| 3845 | ScalarEvolution::getSizeOfScalableVectorExpr(Type *IntTy, | |||
| 3846 | ScalableVectorType *ScalableTy) { | |||
| 3847 | Constant *NullPtr = Constant::getNullValue(ScalableTy->getPointerTo()); | |||
| 3848 | Constant *One = ConstantInt::get(IntTy, 1); | |||
| 3849 | Constant *GEP = ConstantExpr::getGetElementPtr(ScalableTy, NullPtr, One); | |||
| 3850 | // Note that the expression we created is the final expression, we don't | |||
| 3851 | // want to simplify it any further Also, if we call a normal getSCEV(), | |||
| 3852 | // we'll end up in an endless recursion. So just create an SCEVUnknown. | |||
| 3853 | return getUnknown(ConstantExpr::getPtrToInt(GEP, IntTy)); | |||
| 3854 | } | |||
| 3855 | ||||
| 3856 | const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) { | |||
| 3857 | if (auto *ScalableAllocTy = dyn_cast<ScalableVectorType>(AllocTy)) | |||
| 3858 | return getSizeOfScalableVectorExpr(IntTy, ScalableAllocTy); | |||
| 3859 | // We can bypass creating a target-independent constant expression and then | |||
| 3860 | // folding it back into a ConstantInt. This is just a compile-time | |||
| 3861 | // optimization. | |||
| 3862 | return getConstant(IntTy, getDataLayout().getTypeAllocSize(AllocTy)); | |||
| 3863 | } | |||
| 3864 | ||||
| 3865 | const SCEV *ScalarEvolution::getStoreSizeOfExpr(Type *IntTy, Type *StoreTy) { | |||
| 3866 | if (auto *ScalableStoreTy = dyn_cast<ScalableVectorType>(StoreTy)) | |||
| 3867 | return getSizeOfScalableVectorExpr(IntTy, ScalableStoreTy); | |||
| 3868 | // We can bypass creating a target-independent constant expression and then | |||
| 3869 | // folding it back into a ConstantInt. This is just a compile-time | |||
| 3870 | // optimization. | |||
| 3871 | return getConstant(IntTy, getDataLayout().getTypeStoreSize(StoreTy)); | |||
| 3872 | } | |||
| 3873 | ||||
| 3874 | const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy, | |||
| 3875 | StructType *STy, | |||
| 3876 | unsigned FieldNo) { | |||
| 3877 | // We can bypass creating a target-independent constant expression and then | |||
| 3878 | // folding it back into a ConstantInt. This is just a compile-time | |||
| 3879 | // optimization. | |||
| 3880 | return getConstant( | |||
| 3881 | IntTy, getDataLayout().getStructLayout(STy)->getElementOffset(FieldNo)); | |||
| 3882 | } | |||
| 3883 | ||||
| 3884 | const SCEV *ScalarEvolution::getUnknown(Value *V) { | |||
| 3885 | // Don't attempt to do anything other than create a SCEVUnknown object | |||
| 3886 | // here. createSCEV only calls getUnknown after checking for all other | |||
| 3887 | // interesting possibilities, and any other code that calls getUnknown | |||
| 3888 | // is doing so in order to hide a value from SCEV canonicalization. | |||
| 3889 | ||||
| 3890 | FoldingSetNodeID ID; | |||
| 3891 | ID.AddInteger(scUnknown); | |||
| 3892 | ID.AddPointer(V); | |||
| 3893 | void *IP = nullptr; | |||
| 3894 | if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) { | |||
| 3895 | assert(cast<SCEVUnknown>(S)->getValue() == V &&((void)0) | |||
| 3896 | "Stale SCEVUnknown in uniquing map!")((void)0); | |||
| 3897 | return S; | |||
| 3898 | } | |||
| 3899 | SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this, | |||
| 3900 | FirstUnknown); | |||
| 3901 | FirstUnknown = cast<SCEVUnknown>(S); | |||
| 3902 | UniqueSCEVs.InsertNode(S, IP); | |||
| 3903 | return S; | |||
| 3904 | } | |||
| 3905 | ||||
| 3906 | //===----------------------------------------------------------------------===// | |||
| 3907 | // Basic SCEV Analysis and PHI Idiom Recognition Code | |||
| 3908 | // | |||
| 3909 | ||||
| 3910 | /// Test if values of the given type are analyzable within the SCEV | |||
| 3911 | /// framework. This primarily includes integer types, and it can optionally | |||
| 3912 | /// include pointer types if the ScalarEvolution class has access to | |||
| 3913 | /// target-specific information. | |||
| 3914 | bool ScalarEvolution::isSCEVable(Type *Ty) const { | |||
| 3915 | // Integers and pointers are always SCEVable. | |||
| 3916 | return Ty->isIntOrPtrTy(); | |||
| 3917 | } | |||
| 3918 | ||||
| 3919 | /// Return the size in bits of the specified type, for which isSCEVable must | |||
| 3920 | /// return true. | |||
| 3921 | uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const { | |||
| 3922 | assert(isSCEVable(Ty) && "Type is not SCEVable!")((void)0); | |||
| 3923 | if (Ty->isPointerTy()) | |||
| ||||
| 3924 | return getDataLayout().getIndexTypeSizeInBits(Ty); | |||
| 3925 | return getDataLayout().getTypeSizeInBits(Ty); | |||
| 3926 | } | |||
| 3927 | ||||
| 3928 | /// Return a type with the same bitwidth as the given type and which represents | |||
| 3929 | /// how SCEV will treat the given type, for which isSCEVable must return | |||
| 3930 | /// true. For pointer types, this is the pointer index sized integer type. | |||
| 3931 | Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const { | |||
| 3932 | assert(isSCEVable(Ty) && "Type is not SCEVable!")((void)0); | |||
| 3933 | ||||
| 3934 | if (Ty->isIntegerTy()) | |||
| 3935 | return Ty; | |||
| 3936 | ||||
| 3937 | // The only other support type is pointer. | |||
| 3938 | assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!")((void)0); | |||
| 3939 | return getDataLayout().getIndexType(Ty); | |||
| 3940 | } | |||
| 3941 | ||||
| 3942 | Type *ScalarEvolution::getWiderType(Type *T1, Type *T2) const { | |||
| 3943 | return getTypeSizeInBits(T1) >= getTypeSizeInBits(T2) ? T1 : T2; | |||
| 3944 | } | |||
| 3945 | ||||
| 3946 | const SCEV *ScalarEvolution::getCouldNotCompute() { | |||
| 3947 | return CouldNotCompute.get(); | |||
| 3948 | } | |||
| 3949 | ||||
| 3950 | bool ScalarEvolution::checkValidity(const SCEV *S) const { | |||
| 3951 | bool ContainsNulls = SCEVExprContains(S, [](const SCEV *S) { | |||
| 3952 | auto *SU = dyn_cast<SCEVUnknown>(S); | |||
| 3953 | return SU && SU->getValue() == nullptr; | |||
| 3954 | }); | |||
| 3955 | ||||
| 3956 | return !ContainsNulls; | |||
| 3957 | } | |||
| 3958 | ||||
| 3959 | bool ScalarEvolution::containsAddRecurrence(const SCEV *S) { | |||
| 3960 | HasRecMapType::iterator I = HasRecMap.find(S); | |||
| 3961 | if (I != HasRecMap.end()) | |||
| 3962 | return I->second; | |||
| 3963 | ||||
| 3964 | bool FoundAddRec = | |||
| 3965 | SCEVExprContains(S, [](const SCEV *S) { return isa<SCEVAddRecExpr>(S); }); | |||
| 3966 | HasRecMap.insert({S, FoundAddRec}); | |||
| 3967 | return FoundAddRec; | |||
| 3968 | } | |||
| 3969 | ||||
| 3970 | /// Try to split a SCEVAddExpr into a pair of {SCEV, ConstantInt}. | |||
| 3971 | /// If \p S is a SCEVAddExpr and is composed of a sub SCEV S' and an | |||
| 3972 | /// offset I, then return {S', I}, else return {\p S, nullptr}. | |||
| 3973 | static std::pair<const SCEV *, ConstantInt *> splitAddExpr(const SCEV *S) { | |||
| 3974 | const auto *Add = dyn_cast<SCEVAddExpr>(S); | |||
| 3975 | if (!Add) | |||
| 3976 | return {S, nullptr}; | |||
| 3977 | ||||
| 3978 | if (Add->getNumOperands() != 2) | |||
| 3979 | return {S, nullptr}; | |||
| 3980 | ||||
| 3981 | auto *ConstOp = dyn_cast<SCEVConstant>(Add->getOperand(0)); | |||
| 3982 | if (!ConstOp) | |||
| 3983 | return {S, nullptr}; | |||
| 3984 | ||||
| 3985 | return {Add->getOperand(1), ConstOp->getValue()}; | |||
| 3986 | } | |||
| 3987 | ||||
| 3988 | /// Return the ValueOffsetPair set for \p S. \p S can be represented | |||
| 3989 | /// by the value and offset from any ValueOffsetPair in the set. | |||
| 3990 | ScalarEvolution::ValueOffsetPairSetVector * | |||
| 3991 | ScalarEvolution::getSCEVValues(const SCEV *S) { | |||
| 3992 | ExprValueMapType::iterator SI = ExprValueMap.find_as(S); | |||
| 3993 | if (SI == ExprValueMap.end()) | |||
| 3994 | return nullptr; | |||
| 3995 | #ifndef NDEBUG1 | |||
| 3996 | if (VerifySCEVMap) { | |||
| 3997 | // Check there is no dangling Value in the set returned. | |||
| 3998 | for (const auto &VE : SI->second) | |||
| 3999 | assert(ValueExprMap.count(VE.first))((void)0); | |||
| 4000 | } | |||
| 4001 | #endif | |||
| 4002 | return &SI->second; | |||
| 4003 | } | |||
| 4004 | ||||
| 4005 | /// Erase Value from ValueExprMap and ExprValueMap. ValueExprMap.erase(V) | |||
| 4006 | /// cannot be used separately. eraseValueFromMap should be used to remove | |||
| 4007 | /// V from ValueExprMap and ExprValueMap at the same time. | |||
| 4008 | void ScalarEvolution::eraseValueFromMap(Value *V) { | |||
| 4009 | ValueExprMapType::iterator I = ValueExprMap.find_as(V); | |||
| 4010 | if (I != ValueExprMap.end()) { | |||
| 4011 | const SCEV *S = I->second; | |||
| 4012 | // Remove {V, 0} from the set of ExprValueMap[S] | |||
| 4013 | if (auto *SV = getSCEVValues(S)) | |||
| 4014 | SV->remove({V, nullptr}); | |||
| 4015 | ||||
| 4016 | // Remove {V, Offset} from the set of ExprValueMap[Stripped] | |||
| 4017 | const SCEV *Stripped; | |||
| 4018 | ConstantInt *Offset; | |||
| 4019 | std::tie(Stripped, Offset) = splitAddExpr(S); | |||
| 4020 | if (Offset != nullptr) { | |||
| 4021 | if (auto *SV = getSCEVValues(Stripped)) | |||
| 4022 | SV->remove({V, Offset}); | |||
| 4023 | } | |||
| 4024 | ValueExprMap.erase(V); | |||
| 4025 | } | |||
| 4026 | } | |||
| 4027 | ||||
| 4028 | /// Check whether value has nuw/nsw/exact set but SCEV does not. | |||
| 4029 | /// TODO: In reality it is better to check the poison recursively | |||
| 4030 | /// but this is better than nothing. | |||
| 4031 | static bool SCEVLostPoisonFlags(const SCEV *S, const Value *V) { | |||
| 4032 | if (auto *I = dyn_cast<Instruction>(V)) { | |||
| 4033 | if (isa<OverflowingBinaryOperator>(I)) { | |||
| 4034 | if (auto *NS = dyn_cast<SCEVNAryExpr>(S)) { | |||
| 4035 | if (I->hasNoSignedWrap() && !NS->hasNoSignedWrap()) | |||
| 4036 | return true; | |||
| 4037 | if (I->hasNoUnsignedWrap() && !NS->hasNoUnsignedWrap()) | |||
| 4038 | return true; | |||
| 4039 | } | |||
| 4040 | } else if (isa<PossiblyExactOperator>(I) && I->isExact()) | |||
| 4041 | return true; | |||
| 4042 | } | |||
| 4043 | return false; | |||
| 4044 | } | |||
| 4045 | ||||
| 4046 | /// Return an existing SCEV if it exists, otherwise analyze the expression and | |||
| 4047 | /// create a new one. | |||
| 4048 | const SCEV *ScalarEvolution::getSCEV(Value *V) { | |||
| 4049 | assert(isSCEVable(V->getType()) && "Value is not SCEVable!")((void)0); | |||
| 4050 | ||||
| 4051 | const SCEV *S = getExistingSCEV(V); | |||
| 4052 | if (S == nullptr) { | |||
| 4053 | S = createSCEV(V); | |||
| 4054 | // During PHI resolution, it is possible to create two SCEVs for the same | |||
| 4055 | // V, so it is needed to double check whether V->S is inserted into | |||
| 4056 | // ValueExprMap before insert S->{V, 0} into ExprValueMap. | |||
| 4057 | std::pair<ValueExprMapType::iterator, bool> Pair = | |||
| 4058 | ValueExprMap.insert({SCEVCallbackVH(V, this), S}); | |||
| 4059 | if (Pair.second && !SCEVLostPoisonFlags(S, V)) { | |||
| 4060 | ExprValueMap[S].insert({V, nullptr}); | |||
| 4061 | ||||
| 4062 | // If S == Stripped + Offset, add Stripped -> {V, Offset} into | |||
| 4063 | // ExprValueMap. | |||
| 4064 | const SCEV *Stripped = S; | |||
| 4065 | ConstantInt *Offset = nullptr; | |||
| 4066 | std::tie(Stripped, Offset) = splitAddExpr(S); | |||
| 4067 | // If stripped is SCEVUnknown, don't bother to save | |||
| 4068 | // Stripped -> {V, offset}. It doesn't simplify and sometimes even | |||
| 4069 | // increase the complexity of the expansion code. | |||
| 4070 | // If V is GetElementPtrInst, don't save Stripped -> {V, offset} | |||
| 4071 | // because it may generate add/sub instead of GEP in SCEV expansion. | |||
| 4072 | if (Offset != nullptr && !isa<SCEVUnknown>(Stripped) && | |||
| 4073 | !isa<GetElementPtrInst>(V)) | |||
| 4074 | ExprValueMap[Stripped].insert({V, Offset}); | |||
| 4075 | } | |||
| 4076 | } | |||
| 4077 | return S; | |||
| 4078 | } | |||
| 4079 | ||||
| 4080 | const SCEV *ScalarEvolution::getExistingSCEV(Value *V) { | |||
| 4081 | assert(isSCEVable(V->getType()) && "Value is not SCEVable!")((void)0); | |||
| 4082 | ||||
| 4083 | ValueExprMapType::iterator I = ValueExprMap.find_as(V); | |||
| 4084 | if (I != ValueExprMap.end()) { | |||
| 4085 | const SCEV *S = I->second; | |||
| 4086 | if (checkValidity(S)) | |||
| 4087 | return S; | |||
| 4088 | eraseValueFromMap(V); | |||
| 4089 | forgetMemoizedResults(S); | |||
| 4090 | } | |||
| 4091 | return nullptr; | |||
| 4092 | } | |||
| 4093 | ||||
| 4094 | /// Return a SCEV corresponding to -V = -1*V | |||
| 4095 | const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V, | |||
| 4096 | SCEV::NoWrapFlags Flags) { | |||
| 4097 | if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V)) | |||
| 4098 | return getConstant( | |||
| 4099 | cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue()))); | |||
| 4100 | ||||
| 4101 | Type *Ty = V->getType(); | |||
| 4102 | Ty = getEffectiveSCEVType(Ty); | |||
| 4103 | return getMulExpr(V, getMinusOne(Ty), Flags); | |||
| 4104 | } | |||
| 4105 | ||||
| 4106 | /// If Expr computes ~A, return A else return nullptr | |||
| 4107 | static const SCEV *MatchNotExpr(const SCEV *Expr) { | |||
| 4108 | const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Expr); | |||
| 4109 | if (!Add || Add->getNumOperands() != 2 || | |||
| 4110 | !Add->getOperand(0)->isAllOnesValue()) | |||
| 4111 | return nullptr; | |||
| 4112 | ||||
| 4113 | const SCEVMulExpr *AddRHS = dyn_cast<SCEVMulExpr>(Add->getOperand(1)); | |||
| 4114 | if (!AddRHS || AddRHS->getNumOperands() != 2 || | |||
| 4115 | !AddRHS->getOperand(0)->isAllOnesValue()) | |||
| 4116 | return nullptr; | |||
| 4117 | ||||
| 4118 | return AddRHS->getOperand(1); | |||
| 4119 | } | |||
| 4120 | ||||
| 4121 | /// Return a SCEV corresponding to ~V = -1-V | |||
| 4122 | const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) { | |||
| 4123 | if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V)) | |||
| 4124 | return getConstant( | |||
| 4125 | cast<ConstantInt>(ConstantExpr::getNot(VC->getValue()))); | |||
| 4126 | ||||
| 4127 | // Fold ~(u|s)(min|max)(~x, ~y) to (u|s)(max|min)(x, y) | |||
| 4128 | if (const SCEVMinMaxExpr *MME = dyn_cast<SCEVMinMaxExpr>(V)) { | |||
| 4129 | auto MatchMinMaxNegation = [&](const SCEVMinMaxExpr *MME) { | |||
| 4130 | SmallVector<const SCEV *, 2> MatchedOperands; | |||
| 4131 | for (const SCEV *Operand : MME->operands()) { | |||
| 4132 | const SCEV *Matched = MatchNotExpr(Operand); | |||
| 4133 | if (!Matched) | |||
| 4134 | return (const SCEV *)nullptr; | |||
| 4135 | MatchedOperands.push_back(Matched); | |||
| 4136 | } | |||
| 4137 | return getMinMaxExpr(SCEVMinMaxExpr::negate(MME->getSCEVType()), | |||
| 4138 | MatchedOperands); | |||
| 4139 | }; | |||
| 4140 | if (const SCEV *Replaced = MatchMinMaxNegation(MME)) | |||
| 4141 | return Replaced; | |||
| 4142 | } | |||
| 4143 | ||||
| 4144 | Type *Ty = V->getType(); | |||
| 4145 | Ty = getEffectiveSCEVType(Ty); | |||
| 4146 | return getMinusSCEV(getMinusOne(Ty), V); | |||
| 4147 | } | |||
| 4148 | ||||
| 4149 | /// Compute an expression equivalent to S - getPointerBase(S). | |||
| 4150 | static const SCEV *removePointerBase(ScalarEvolution *SE, const SCEV *P) { | |||
| 4151 | assert(P->getType()->isPointerTy())((void)0); | |||
| 4152 | ||||
| 4153 | if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(P)) { | |||
| 4154 | // The base of an AddRec is the first operand. | |||
| 4155 | SmallVector<const SCEV *> Ops{AddRec->operands()}; | |||
| 4156 | Ops[0] = removePointerBase(SE, Ops[0]); | |||
| 4157 | // Don't try to transfer nowrap flags for now. We could in some cases | |||
| 4158 | // (for example, if pointer operand of the AddRec is a SCEVUnknown). | |||
| 4159 | return SE->getAddRecExpr(Ops, AddRec->getLoop(), SCEV::FlagAnyWrap); | |||
| 4160 | } | |||
| 4161 | if (auto *Add = dyn_cast<SCEVAddExpr>(P)) { | |||
| 4162 | // The base of an Add is the pointer operand. | |||
| 4163 | SmallVector<const SCEV *> Ops{Add->operands()}; | |||
| 4164 | const SCEV **PtrOp = nullptr; | |||
| 4165 | for (const SCEV *&AddOp : Ops) { | |||
| 4166 | if (AddOp->getType()->isPointerTy()) { | |||
| 4167 | // If we find an Add with multiple pointer operands, treat it as a | |||
| 4168 | // pointer base to be consistent with getPointerBase. Eventually | |||
| 4169 | // we should be able to assert this is impossible. | |||
| 4170 | if (PtrOp) | |||
| 4171 | return SE->getZero(P->getType()); | |||
| 4172 | PtrOp = &AddOp; | |||
| 4173 | } | |||
| 4174 | } | |||
| 4175 | *PtrOp = removePointerBase(SE, *PtrOp); | |||
| 4176 | // Don't try to transfer nowrap flags for now. We could in some cases | |||
| 4177 | // (for example, if the pointer operand of the Add is a SCEVUnknown). | |||
| 4178 | return SE->getAddExpr(Ops); | |||
| 4179 | } | |||
| 4180 | // Any other expression must be a pointer base. | |||
| 4181 | return SE->getZero(P->getType()); | |||
| 4182 | } | |||
| 4183 | ||||
| 4184 | const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS, | |||
| 4185 | SCEV::NoWrapFlags Flags, | |||
| 4186 | unsigned Depth) { | |||
| 4187 | // Fast path: X - X --> 0. | |||
| 4188 | if (LHS == RHS) | |||
| 4189 | return getZero(LHS->getType()); | |||
| 4190 | ||||
| 4191 | // If we subtract two pointers with different pointer bases, bail. | |||
| 4192 | // Eventually, we're going to add an assertion to getMulExpr that we | |||
| 4193 | // can't multiply by a pointer. | |||
| 4194 | if (RHS->getType()->isPointerTy()) { | |||
| 4195 | if (!LHS->getType()->isPointerTy() || | |||
| 4196 | getPointerBase(LHS) != getPointerBase(RHS)) | |||
| 4197 | return getCouldNotCompute(); | |||
| 4198 | LHS = removePointerBase(this, LHS); | |||
| 4199 | RHS = removePointerBase(this, RHS); | |||
| 4200 | } | |||
| 4201 | ||||
| 4202 | // We represent LHS - RHS as LHS + (-1)*RHS. This transformation | |||
| 4203 | // makes it so that we cannot make much use of NUW. | |||
| 4204 | auto AddFlags = SCEV::FlagAnyWrap; | |||
| 4205 | const bool RHSIsNotMinSigned = | |||
| 4206 | !getSignedRangeMin(RHS).isMinSignedValue(); | |||
| 4207 | if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) { | |||
| 4208 | // Let M be the minimum representable signed value. Then (-1)*RHS | |||
| 4209 | // signed-wraps if and only if RHS is M. That can happen even for | |||
| 4210 | // a NSW subtraction because e.g. (-1)*M signed-wraps even though | |||
| 4211 | // -1 - M does not. So to transfer NSW from LHS - RHS to LHS + | |||
| 4212 | // (-1)*RHS, we need to prove that RHS != M. | |||
| 4213 | // | |||
| 4214 | // If LHS is non-negative and we know that LHS - RHS does not | |||
| 4215 | // signed-wrap, then RHS cannot be M. So we can rule out signed-wrap | |||
| 4216 | // either by proving that RHS > M or that LHS >= 0. | |||
| 4217 | if (RHSIsNotMinSigned || isKnownNonNegative(LHS)) { | |||
| 4218 | AddFlags = SCEV::FlagNSW; | |||
| 4219 | } | |||
| 4220 | } | |||
| 4221 | ||||
| 4222 | // FIXME: Find a correct way to transfer NSW to (-1)*M when LHS - | |||
| 4223 | // RHS is NSW and LHS >= 0. | |||
| 4224 | // | |||
| 4225 | // The difficulty here is that the NSW flag may have been proven | |||
| 4226 | // relative to a loop that is to be found in a recurrence in LHS and | |||
| 4227 | // not in RHS. Applying NSW to (-1)*M may then let the NSW have a | |||
| 4228 | // larger scope than intended. | |||
| 4229 | auto NegFlags = RHSIsNotMinSigned ? SCEV::FlagNSW : SCEV::FlagAnyWrap; | |||
| 4230 | ||||
| 4231 | return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags, Depth); | |||
| 4232 | } | |||
| 4233 | ||||
| 4234 | const SCEV *ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty, | |||
| 4235 | unsigned Depth) { | |||
| 4236 | Type *SrcTy = V->getType(); | |||
| 4237 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4238 | "Cannot truncate or zero extend with non-integer arguments!")((void)0); | |||
| 4239 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4240 | return V; // No conversion | |||
| 4241 | if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty)) | |||
| 4242 | return getTruncateExpr(V, Ty, Depth); | |||
| 4243 | return getZeroExtendExpr(V, Ty, Depth); | |||
| 4244 | } | |||
| 4245 | ||||
| 4246 | const SCEV *ScalarEvolution::getTruncateOrSignExtend(const SCEV *V, Type *Ty, | |||
| 4247 | unsigned Depth) { | |||
| 4248 | Type *SrcTy = V->getType(); | |||
| 4249 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4250 | "Cannot truncate or zero extend with non-integer arguments!")((void)0); | |||
| 4251 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4252 | return V; // No conversion | |||
| 4253 | if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty)) | |||
| 4254 | return getTruncateExpr(V, Ty, Depth); | |||
| 4255 | return getSignExtendExpr(V, Ty, Depth); | |||
| 4256 | } | |||
| 4257 | ||||
| 4258 | const SCEV * | |||
| 4259 | ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) { | |||
| 4260 | Type *SrcTy = V->getType(); | |||
| 4261 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4262 | "Cannot noop or zero extend with non-integer arguments!")((void)0); | |||
| 4263 | assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((void)0) | |||
| 4264 | "getNoopOrZeroExtend cannot truncate!")((void)0); | |||
| 4265 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4266 | return V; // No conversion | |||
| 4267 | return getZeroExtendExpr(V, Ty); | |||
| 4268 | } | |||
| 4269 | ||||
| 4270 | const SCEV * | |||
| 4271 | ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) { | |||
| 4272 | Type *SrcTy = V->getType(); | |||
| 4273 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4274 | "Cannot noop or sign extend with non-integer arguments!")((void)0); | |||
| 4275 | assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((void)0) | |||
| 4276 | "getNoopOrSignExtend cannot truncate!")((void)0); | |||
| 4277 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4278 | return V; // No conversion | |||
| 4279 | return getSignExtendExpr(V, Ty); | |||
| 4280 | } | |||
| 4281 | ||||
| 4282 | const SCEV * | |||
| 4283 | ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) { | |||
| 4284 | Type *SrcTy = V->getType(); | |||
| 4285 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4286 | "Cannot noop or any extend with non-integer arguments!")((void)0); | |||
| 4287 | assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((void)0) | |||
| 4288 | "getNoopOrAnyExtend cannot truncate!")((void)0); | |||
| 4289 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4290 | return V; // No conversion | |||
| 4291 | return getAnyExtendExpr(V, Ty); | |||
| 4292 | } | |||
| 4293 | ||||
| 4294 | const SCEV * | |||
| 4295 | ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) { | |||
| 4296 | Type *SrcTy = V->getType(); | |||
| 4297 | assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&((void)0) | |||
| 4298 | "Cannot truncate or noop with non-integer arguments!")((void)0); | |||
| 4299 | assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&((void)0) | |||
| 4300 | "getTruncateOrNoop cannot extend!")((void)0); | |||
| 4301 | if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty)) | |||
| 4302 | return V; // No conversion | |||
| 4303 | return getTruncateExpr(V, Ty); | |||
| 4304 | } | |||
| 4305 | ||||
| 4306 | const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS, | |||
| 4307 | const SCEV *RHS) { | |||
| 4308 | const SCEV *PromotedLHS = LHS; | |||
| 4309 | const SCEV *PromotedRHS = RHS; | |||
| 4310 | ||||
| 4311 | if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType())) | |||
| 4312 | PromotedRHS = getZeroExtendExpr(RHS, LHS->getType()); | |||
| 4313 | else | |||
| 4314 | PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType()); | |||
| 4315 | ||||
| 4316 | return getUMaxExpr(PromotedLHS, PromotedRHS); | |||
| 4317 | } | |||
| 4318 | ||||
| 4319 | const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS, | |||
| 4320 | const SCEV *RHS) { | |||
| 4321 | SmallVector<const SCEV *, 2> Ops = { LHS, RHS }; | |||
| 4322 | return getUMinFromMismatchedTypes(Ops); | |||
| 4323 | } | |||
| 4324 | ||||
| 4325 | const SCEV *ScalarEvolution::getUMinFromMismatchedTypes( | |||
| 4326 | SmallVectorImpl<const SCEV *> &Ops) { | |||
| 4327 | assert(!Ops.empty() && "At least one operand must be!")((void)0); | |||
| 4328 | // Trivial case. | |||
| 4329 | if (Ops.size() == 1) | |||
| 4330 | return Ops[0]; | |||
| 4331 | ||||
| 4332 | // Find the max type first. | |||
| 4333 | Type *MaxType = nullptr; | |||
| 4334 | for (auto *S : Ops) | |||
| 4335 | if (MaxType) | |||
| 4336 | MaxType = getWiderType(MaxType, S->getType()); | |||
| 4337 | else | |||
| 4338 | MaxType = S->getType(); | |||
| 4339 | assert(MaxType && "Failed to find maximum type!")((void)0); | |||
| 4340 | ||||
| 4341 | // Extend all ops to max type. | |||
| 4342 | SmallVector<const SCEV *, 2> PromotedOps; | |||
| 4343 | for (auto *S : Ops) | |||
| 4344 | PromotedOps.push_back(getNoopOrZeroExtend(S, MaxType)); | |||
| 4345 | ||||
| 4346 | // Generate umin. | |||
| 4347 | return getUMinExpr(PromotedOps); | |||
| 4348 | } | |||
| 4349 | ||||
| 4350 | const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) { | |||
| 4351 | // A pointer operand may evaluate to a nonpointer expression, such as null. | |||
| 4352 | if (!V->getType()->isPointerTy()) | |||
| 4353 | return V; | |||
| 4354 | ||||
| 4355 | while (true) { | |||
| 4356 | if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(V)) { | |||
| 4357 | V = AddRec->getStart(); | |||
| 4358 | } else if (auto *Add = dyn_cast<SCEVAddExpr>(V)) { | |||
| 4359 | const SCEV *PtrOp = nullptr; | |||
| 4360 | for (const SCEV *AddOp : Add->operands()) { | |||
| 4361 | if (AddOp->getType()->isPointerTy()) { | |||
| 4362 | // Cannot find the base of an expression with multiple pointer ops. | |||
| 4363 | if (PtrOp) | |||
| 4364 | return V; | |||
| 4365 | PtrOp = AddOp; | |||
| 4366 | } | |||
| 4367 | } | |||
| 4368 | if (!PtrOp) // All operands were non-pointer. | |||
| 4369 | return V; | |||
| 4370 | V = PtrOp; | |||
| 4371 | } else // Not something we can look further into. | |||
| 4372 | return V; | |||
| 4373 | } | |||
| 4374 | } | |||
| 4375 | ||||
| 4376 | /// Push users of the given Instruction onto the given Worklist. | |||
| 4377 | static void | |||
| 4378 | PushDefUseChildren(Instruction *I, | |||
| 4379 | SmallVectorImpl<Instruction *> &Worklist) { | |||
| 4380 | // Push the def-use children onto the Worklist stack. | |||
| 4381 | for (User *U : I->users()) | |||
| 4382 | Worklist.push_back(cast<Instruction>(U)); | |||
| 4383 | } | |||
| 4384 | ||||
| 4385 | void ScalarEvolution::forgetSymbolicName(Instruction *PN, const SCEV *SymName) { | |||
| 4386 | SmallVector<Instruction *, 16> Worklist; | |||
| 4387 | PushDefUseChildren(PN, Worklist); | |||
| 4388 | ||||
| 4389 | SmallPtrSet<Instruction *, 8> Visited; | |||
| 4390 | Visited.insert(PN); | |||
| 4391 | while (!Worklist.empty()) { | |||
| 4392 | Instruction *I = Worklist.pop_back_val(); | |||
| 4393 | if (!Visited.insert(I).second) | |||
| 4394 | continue; | |||
| 4395 | ||||
| 4396 | auto It = ValueExprMap.find_as(static_cast<Value *>(I)); | |||
| 4397 | if (It != ValueExprMap.end()) { | |||
| 4398 | const SCEV *Old = It->second; | |||
| 4399 | ||||
| 4400 | // Short-circuit the def-use traversal if the symbolic name | |||
| 4401 | // ceases to appear in expressions. | |||
| 4402 | if (Old != SymName && !hasOperand(Old, SymName)) | |||
| 4403 | continue; | |||
| 4404 | ||||
| 4405 | // SCEVUnknown for a PHI either means that it has an unrecognized | |||
| 4406 | // structure, it's a PHI that's in the progress of being computed | |||
| 4407 | // by createNodeForPHI, or it's a single-value PHI. In the first case, | |||
| 4408 | // additional loop trip count information isn't going to change anything. | |||
| 4409 | // In the second case, createNodeForPHI will perform the necessary | |||
| 4410 | // updates on its own when it gets to that point. In the third, we do | |||
| 4411 | // want to forget the SCEVUnknown. | |||
| 4412 | if (!isa<PHINode>(I) || | |||
| 4413 | !isa<SCEVUnknown>(Old) || | |||
| 4414 | (I != PN && Old == SymName)) { | |||
| 4415 | eraseValueFromMap(It->first); | |||
| 4416 | forgetMemoizedResults(Old); | |||
| 4417 | } | |||
| 4418 | } | |||
| 4419 | ||||
| 4420 | PushDefUseChildren(I, Worklist); | |||
| 4421 | } | |||
| 4422 | } | |||
| 4423 | ||||
| 4424 | namespace { | |||
| 4425 | ||||
| 4426 | /// Takes SCEV S and Loop L. For each AddRec sub-expression, use its start | |||
| 4427 | /// expression in case its Loop is L. If it is not L then | |||
| 4428 | /// if IgnoreOtherLoops is true then use AddRec itself | |||
| 4429 | /// otherwise rewrite cannot be done. | |||
| 4430 | /// If SCEV contains non-invariant unknown SCEV rewrite cannot be done. | |||
| 4431 | class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> { | |||
| 4432 | public: | |||
| 4433 | static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE, | |||
| 4434 | bool IgnoreOtherLoops = true) { | |||
| 4435 | SCEVInitRewriter Rewriter(L, SE); | |||
| 4436 | const SCEV *Result = Rewriter.visit(S); | |||
| 4437 | if (Rewriter.hasSeenLoopVariantSCEVUnknown()) | |||
| 4438 | return SE.getCouldNotCompute(); | |||
| 4439 | return Rewriter.hasSeenOtherLoops() && !IgnoreOtherLoops | |||
| 4440 | ? SE.getCouldNotCompute() | |||
| 4441 | : Result; | |||
| 4442 | } | |||
| 4443 | ||||
| 4444 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 4445 | if (!SE.isLoopInvariant(Expr, L)) | |||
| 4446 | SeenLoopVariantSCEVUnknown = true; | |||
| 4447 | return Expr; | |||
| 4448 | } | |||
| 4449 | ||||
| 4450 | const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { | |||
| 4451 | // Only re-write AddRecExprs for this loop. | |||
| 4452 | if (Expr->getLoop() == L) | |||
| 4453 | return Expr->getStart(); | |||
| 4454 | SeenOtherLoops = true; | |||
| 4455 | return Expr; | |||
| 4456 | } | |||
| 4457 | ||||
| 4458 | bool hasSeenLoopVariantSCEVUnknown() { return SeenLoopVariantSCEVUnknown; } | |||
| 4459 | ||||
| 4460 | bool hasSeenOtherLoops() { return SeenOtherLoops; } | |||
| 4461 | ||||
| 4462 | private: | |||
| 4463 | explicit SCEVInitRewriter(const Loop *L, ScalarEvolution &SE) | |||
| 4464 | : SCEVRewriteVisitor(SE), L(L) {} | |||
| 4465 | ||||
| 4466 | const Loop *L; | |||
| 4467 | bool SeenLoopVariantSCEVUnknown = false; | |||
| 4468 | bool SeenOtherLoops = false; | |||
| 4469 | }; | |||
| 4470 | ||||
| 4471 | /// Takes SCEV S and Loop L. For each AddRec sub-expression, use its post | |||
| 4472 | /// increment expression in case its Loop is L. If it is not L then | |||
| 4473 | /// use AddRec itself. | |||
| 4474 | /// If SCEV contains non-invariant unknown SCEV rewrite cannot be done. | |||
| 4475 | class SCEVPostIncRewriter : public SCEVRewriteVisitor<SCEVPostIncRewriter> { | |||
| 4476 | public: | |||
| 4477 | static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE) { | |||
| 4478 | SCEVPostIncRewriter Rewriter(L, SE); | |||
| 4479 | const SCEV *Result = Rewriter.visit(S); | |||
| 4480 | return Rewriter.hasSeenLoopVariantSCEVUnknown() | |||
| 4481 | ? SE.getCouldNotCompute() | |||
| 4482 | : Result; | |||
| 4483 | } | |||
| 4484 | ||||
| 4485 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 4486 | if (!SE.isLoopInvariant(Expr, L)) | |||
| 4487 | SeenLoopVariantSCEVUnknown = true; | |||
| 4488 | return Expr; | |||
| 4489 | } | |||
| 4490 | ||||
| 4491 | const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { | |||
| 4492 | // Only re-write AddRecExprs for this loop. | |||
| 4493 | if (Expr->getLoop() == L) | |||
| 4494 | return Expr->getPostIncExpr(SE); | |||
| 4495 | SeenOtherLoops = true; | |||
| 4496 | return Expr; | |||
| 4497 | } | |||
| 4498 | ||||
| 4499 | bool hasSeenLoopVariantSCEVUnknown() { return SeenLoopVariantSCEVUnknown; } | |||
| 4500 | ||||
| 4501 | bool hasSeenOtherLoops() { return SeenOtherLoops; } | |||
| 4502 | ||||
| 4503 | private: | |||
| 4504 | explicit SCEVPostIncRewriter(const Loop *L, ScalarEvolution &SE) | |||
| 4505 | : SCEVRewriteVisitor(SE), L(L) {} | |||
| 4506 | ||||
| 4507 | const Loop *L; | |||
| 4508 | bool SeenLoopVariantSCEVUnknown = false; | |||
| 4509 | bool SeenOtherLoops = false; | |||
| 4510 | }; | |||
| 4511 | ||||
| 4512 | /// This class evaluates the compare condition by matching it against the | |||
| 4513 | /// condition of loop latch. If there is a match we assume a true value | |||
| 4514 | /// for the condition while building SCEV nodes. | |||
| 4515 | class SCEVBackedgeConditionFolder | |||
| 4516 | : public SCEVRewriteVisitor<SCEVBackedgeConditionFolder> { | |||
| 4517 | public: | |||
| 4518 | static const SCEV *rewrite(const SCEV *S, const Loop *L, | |||
| 4519 | ScalarEvolution &SE) { | |||
| 4520 | bool IsPosBECond = false; | |||
| 4521 | Value *BECond = nullptr; | |||
| 4522 | if (BasicBlock *Latch = L->getLoopLatch()) { | |||
| 4523 | BranchInst *BI = dyn_cast<BranchInst>(Latch->getTerminator()); | |||
| 4524 | if (BI && BI->isConditional()) { | |||
| 4525 | assert(BI->getSuccessor(0) != BI->getSuccessor(1) &&((void)0) | |||
| 4526 | "Both outgoing branches should not target same header!")((void)0); | |||
| 4527 | BECond = BI->getCondition(); | |||
| 4528 | IsPosBECond = BI->getSuccessor(0) == L->getHeader(); | |||
| 4529 | } else { | |||
| 4530 | return S; | |||
| 4531 | } | |||
| 4532 | } | |||
| 4533 | SCEVBackedgeConditionFolder Rewriter(L, BECond, IsPosBECond, SE); | |||
| 4534 | return Rewriter.visit(S); | |||
| 4535 | } | |||
| 4536 | ||||
| 4537 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 4538 | const SCEV *Result = Expr; | |||
| 4539 | bool InvariantF = SE.isLoopInvariant(Expr, L); | |||
| 4540 | ||||
| 4541 | if (!InvariantF) { | |||
| 4542 | Instruction *I = cast<Instruction>(Expr->getValue()); | |||
| 4543 | switch (I->getOpcode()) { | |||
| 4544 | case Instruction::Select: { | |||
| 4545 | SelectInst *SI = cast<SelectInst>(I); | |||
| 4546 | Optional<const SCEV *> Res = | |||
| 4547 | compareWithBackedgeCondition(SI->getCondition()); | |||
| 4548 | if (Res.hasValue()) { | |||
| 4549 | bool IsOne = cast<SCEVConstant>(Res.getValue())->getValue()->isOne(); | |||
| 4550 | Result = SE.getSCEV(IsOne ? SI->getTrueValue() : SI->getFalseValue()); | |||
| 4551 | } | |||
| 4552 | break; | |||
| 4553 | } | |||
| 4554 | default: { | |||
| 4555 | Optional<const SCEV *> Res = compareWithBackedgeCondition(I); | |||
| 4556 | if (Res.hasValue()) | |||
| 4557 | Result = Res.getValue(); | |||
| 4558 | break; | |||
| 4559 | } | |||
| 4560 | } | |||
| 4561 | } | |||
| 4562 | return Result; | |||
| 4563 | } | |||
| 4564 | ||||
| 4565 | private: | |||
| 4566 | explicit SCEVBackedgeConditionFolder(const Loop *L, Value *BECond, | |||
| 4567 | bool IsPosBECond, ScalarEvolution &SE) | |||
| 4568 | : SCEVRewriteVisitor(SE), L(L), BackedgeCond(BECond), | |||
| 4569 | IsPositiveBECond(IsPosBECond) {} | |||
| 4570 | ||||
| 4571 | Optional<const SCEV *> compareWithBackedgeCondition(Value *IC); | |||
| 4572 | ||||
| 4573 | const Loop *L; | |||
| 4574 | /// Loop back condition. | |||
| 4575 | Value *BackedgeCond = nullptr; | |||
| 4576 | /// Set to true if loop back is on positive branch condition. | |||
| 4577 | bool IsPositiveBECond; | |||
| 4578 | }; | |||
| 4579 | ||||
| 4580 | Optional<const SCEV *> | |||
| 4581 | SCEVBackedgeConditionFolder::compareWithBackedgeCondition(Value *IC) { | |||
| 4582 | ||||
| 4583 | // If value matches the backedge condition for loop latch, | |||
| 4584 | // then return a constant evolution node based on loopback | |||
| 4585 | // branch taken. | |||
| 4586 | if (BackedgeCond == IC) | |||
| 4587 | return IsPositiveBECond ? SE.getOne(Type::getInt1Ty(SE.getContext())) | |||
| 4588 | : SE.getZero(Type::getInt1Ty(SE.getContext())); | |||
| 4589 | return None; | |||
| 4590 | } | |||
| 4591 | ||||
| 4592 | class SCEVShiftRewriter : public SCEVRewriteVisitor<SCEVShiftRewriter> { | |||
| 4593 | public: | |||
| 4594 | static const SCEV *rewrite(const SCEV *S, const Loop *L, | |||
| 4595 | ScalarEvolution &SE) { | |||
| 4596 | SCEVShiftRewriter Rewriter(L, SE); | |||
| 4597 | const SCEV *Result = Rewriter.visit(S); | |||
| 4598 | return Rewriter.isValid() ? Result : SE.getCouldNotCompute(); | |||
| 4599 | } | |||
| 4600 | ||||
| 4601 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 4602 | // Only allow AddRecExprs for this loop. | |||
| 4603 | if (!SE.isLoopInvariant(Expr, L)) | |||
| 4604 | Valid = false; | |||
| 4605 | return Expr; | |||
| 4606 | } | |||
| 4607 | ||||
| 4608 | const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { | |||
| 4609 | if (Expr->getLoop() == L && Expr->isAffine()) | |||
| 4610 | return SE.getMinusSCEV(Expr, Expr->getStepRecurrence(SE)); | |||
| 4611 | Valid = false; | |||
| 4612 | return Expr; | |||
| 4613 | } | |||
| 4614 | ||||
| 4615 | bool isValid() { return Valid; } | |||
| 4616 | ||||
| 4617 | private: | |||
| 4618 | explicit SCEVShiftRewriter(const Loop *L, ScalarEvolution &SE) | |||
| 4619 | : SCEVRewriteVisitor(SE), L(L) {} | |||
| 4620 | ||||
| 4621 | const Loop *L; | |||
| 4622 | bool Valid = true; | |||
| 4623 | }; | |||
| 4624 | ||||
| 4625 | } // end anonymous namespace | |||
| 4626 | ||||
| 4627 | SCEV::NoWrapFlags | |||
| 4628 | ScalarEvolution::proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR) { | |||
| 4629 | if (!AR->isAffine()) | |||
| 4630 | return SCEV::FlagAnyWrap; | |||
| 4631 | ||||
| 4632 | using OBO = OverflowingBinaryOperator; | |||
| 4633 | ||||
| 4634 | SCEV::NoWrapFlags Result = SCEV::FlagAnyWrap; | |||
| 4635 | ||||
| 4636 | if (!AR->hasNoSignedWrap()) { | |||
| 4637 | ConstantRange AddRecRange = getSignedRange(AR); | |||
| 4638 | ConstantRange IncRange = getSignedRange(AR->getStepRecurrence(*this)); | |||
| 4639 | ||||
| 4640 | auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion( | |||
| 4641 | Instruction::Add, IncRange, OBO::NoSignedWrap); | |||
| 4642 | if (NSWRegion.contains(AddRecRange)) | |||
| 4643 | Result = ScalarEvolution::setFlags(Result, SCEV::FlagNSW); | |||
| 4644 | } | |||
| 4645 | ||||
| 4646 | if (!AR->hasNoUnsignedWrap()) { | |||
| 4647 | ConstantRange AddRecRange = getUnsignedRange(AR); | |||
| 4648 | ConstantRange IncRange = getUnsignedRange(AR->getStepRecurrence(*this)); | |||
| 4649 | ||||
| 4650 | auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion( | |||
| 4651 | Instruction::Add, IncRange, OBO::NoUnsignedWrap); | |||
| 4652 | if (NUWRegion.contains(AddRecRange)) | |||
| 4653 | Result = ScalarEvolution::setFlags(Result, SCEV::FlagNUW); | |||
| 4654 | } | |||
| 4655 | ||||
| 4656 | return Result; | |||
| 4657 | } | |||
| 4658 | ||||
| 4659 | SCEV::NoWrapFlags | |||
| 4660 | ScalarEvolution::proveNoSignedWrapViaInduction(const SCEVAddRecExpr *AR) { | |||
| 4661 | SCEV::NoWrapFlags Result = AR->getNoWrapFlags(); | |||
| 4662 | ||||
| 4663 | if (AR->hasNoSignedWrap()) | |||
| 4664 | return Result; | |||
| 4665 | ||||
| 4666 | if (!AR->isAffine()) | |||
| 4667 | return Result; | |||
| 4668 | ||||
| 4669 | const SCEV *Step = AR->getStepRecurrence(*this); | |||
| 4670 | const Loop *L = AR->getLoop(); | |||
| 4671 | ||||
| 4672 | // Check whether the backedge-taken count is SCEVCouldNotCompute. | |||
| 4673 | // Note that this serves two purposes: It filters out loops that are | |||
| 4674 | // simply not analyzable, and it covers the case where this code is | |||
| 4675 | // being called from within backedge-taken count analysis, such that | |||
| 4676 | // attempting to ask for the backedge-taken count would likely result | |||
| 4677 | // in infinite recursion. In the later case, the analysis code will | |||
| 4678 | // cope with a conservative value, and it will take care to purge | |||
| 4679 | // that value once it has finished. | |||
| 4680 | const SCEV *MaxBECount = getConstantMaxBackedgeTakenCount(L); | |||
| 4681 | ||||
| 4682 | // Normally, in the cases we can prove no-overflow via a | |||
| 4683 | // backedge guarding condition, we can also compute a backedge | |||
| 4684 | // taken count for the loop. The exceptions are assumptions and | |||
| 4685 | // guards present in the loop -- SCEV is not great at exploiting | |||
| 4686 | // these to compute max backedge taken counts, but can still use | |||
| 4687 | // these to prove lack of overflow. Use this fact to avoid | |||
| 4688 | // doing extra work that may not pay off. | |||
| 4689 | ||||
| 4690 | if (isa<SCEVCouldNotCompute>(MaxBECount) && !HasGuards && | |||
| 4691 | AC.assumptions().empty()) | |||
| 4692 | return Result; | |||
| 4693 | ||||
| 4694 | // If the backedge is guarded by a comparison with the pre-inc value the | |||
| 4695 | // addrec is safe. Also, if the entry is guarded by a comparison with the | |||
| 4696 | // start value and the backedge is guarded by a comparison with the post-inc | |||
| 4697 | // value, the addrec is safe. | |||
| 4698 | ICmpInst::Predicate Pred; | |||
| 4699 | const SCEV *OverflowLimit = | |||
| 4700 | getSignedOverflowLimitForStep(Step, &Pred, this); | |||
| 4701 | if (OverflowLimit && | |||
| 4702 | (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) || | |||
| 4703 | isKnownOnEveryIteration(Pred, AR, OverflowLimit))) { | |||
| 4704 | Result = setFlags(Result, SCEV::FlagNSW); | |||
| 4705 | } | |||
| 4706 | return Result; | |||
| 4707 | } | |||
| 4708 | SCEV::NoWrapFlags | |||
| 4709 | ScalarEvolution::proveNoUnsignedWrapViaInduction(const SCEVAddRecExpr *AR) { | |||
| 4710 | SCEV::NoWrapFlags Result = AR->getNoWrapFlags(); | |||
| 4711 | ||||
| 4712 | if (AR->hasNoUnsignedWrap()) | |||
| 4713 | return Result; | |||
| 4714 | ||||
| 4715 | if (!AR->isAffine()) | |||
| 4716 | return Result; | |||
| 4717 | ||||
| 4718 | const SCEV *Step = AR->getStepRecurrence(*this); | |||
| 4719 | unsigned BitWidth = getTypeSizeInBits(AR->getType()); | |||
| 4720 | const Loop *L = AR->getLoop(); | |||
| 4721 | ||||
| 4722 | // Check whether the backedge-taken count is SCEVCouldNotCompute. | |||
| 4723 | // Note that this serves two purposes: It filters out loops that are | |||
| 4724 | // simply not analyzable, and it covers the case where this code is | |||
| 4725 | // being called from within backedge-taken count analysis, such that | |||
| 4726 | // attempting to ask for the backedge-taken count would likely result | |||
| 4727 | // in infinite recursion. In the later case, the analysis code will | |||
| 4728 | // cope with a conservative value, and it will take care to purge | |||
| 4729 | // that value once it has finished. | |||
| 4730 | const SCEV *MaxBECount = getConstantMaxBackedgeTakenCount(L); | |||
| 4731 | ||||
| 4732 | // Normally, in the cases we can prove no-overflow via a | |||
| 4733 | // backedge guarding condition, we can also compute a backedge | |||
| 4734 | // taken count for the loop. The exceptions are assumptions and | |||
| 4735 | // guards present in the loop -- SCEV is not great at exploiting | |||
| 4736 | // these to compute max backedge taken counts, but can still use | |||
| 4737 | // these to prove lack of overflow. Use this fact to avoid | |||
| 4738 | // doing extra work that may not pay off. | |||
| 4739 | ||||
| 4740 | if (isa<SCEVCouldNotCompute>(MaxBECount) && !HasGuards && | |||
| 4741 | AC.assumptions().empty()) | |||
| 4742 | return Result; | |||
| 4743 | ||||
| 4744 | // If the backedge is guarded by a comparison with the pre-inc value the | |||
| 4745 | // addrec is safe. Also, if the entry is guarded by a comparison with the | |||
| 4746 | // start value and the backedge is guarded by a comparison with the post-inc | |||
| 4747 | // value, the addrec is safe. | |||
| 4748 | if (isKnownPositive(Step)) { | |||
| 4749 | const SCEV *N = getConstant(APInt::getMinValue(BitWidth) - | |||
| 4750 | getUnsignedRangeMax(Step)); | |||
| 4751 | if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) || | |||
| 4752 | isKnownOnEveryIteration(ICmpInst::ICMP_ULT, AR, N)) { | |||
| 4753 | Result = setFlags(Result, SCEV::FlagNUW); | |||
| 4754 | } | |||
| 4755 | } | |||
| 4756 | ||||
| 4757 | return Result; | |||
| 4758 | } | |||
| 4759 | ||||
| 4760 | namespace { | |||
| 4761 | ||||
| 4762 | /// Represents an abstract binary operation. This may exist as a | |||
| 4763 | /// normal instruction or constant expression, or may have been | |||
| 4764 | /// derived from an expression tree. | |||
| 4765 | struct BinaryOp { | |||
| 4766 | unsigned Opcode; | |||
| 4767 | Value *LHS; | |||
| 4768 | Value *RHS; | |||
| 4769 | bool IsNSW = false; | |||
| 4770 | bool IsNUW = false; | |||
| 4771 | ||||
| 4772 | /// Op is set if this BinaryOp corresponds to a concrete LLVM instruction or | |||
| 4773 | /// constant expression. | |||
| 4774 | Operator *Op = nullptr; | |||
| 4775 | ||||
| 4776 | explicit BinaryOp(Operator *Op) | |||
| 4777 | : Opcode(Op->getOpcode()), LHS(Op->getOperand(0)), RHS(Op->getOperand(1)), | |||
| 4778 | Op(Op) { | |||
| 4779 | if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(Op)) { | |||
| 4780 | IsNSW = OBO->hasNoSignedWrap(); | |||
| 4781 | IsNUW = OBO->hasNoUnsignedWrap(); | |||
| 4782 | } | |||
| 4783 | } | |||
| 4784 | ||||
| 4785 | explicit BinaryOp(unsigned Opcode, Value *LHS, Value *RHS, bool IsNSW = false, | |||
| 4786 | bool IsNUW = false) | |||
| 4787 | : Opcode(Opcode), LHS(LHS), RHS(RHS), IsNSW(IsNSW), IsNUW(IsNUW) {} | |||
| 4788 | }; | |||
| 4789 | ||||
| 4790 | } // end anonymous namespace | |||
| 4791 | ||||
| 4792 | /// Try to map \p V into a BinaryOp, and return \c None on failure. | |||
| 4793 | static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) { | |||
| 4794 | auto *Op = dyn_cast<Operator>(V); | |||
| 4795 | if (!Op) | |||
| 4796 | return None; | |||
| 4797 | ||||
| 4798 | // Implementation detail: all the cleverness here should happen without | |||
| 4799 | // creating new SCEV expressions -- our caller knowns tricks to avoid creating | |||
| 4800 | // SCEV expressions when possible, and we should not break that. | |||
| 4801 | ||||
| 4802 | switch (Op->getOpcode()) { | |||
| 4803 | case Instruction::Add: | |||
| 4804 | case Instruction::Sub: | |||
| 4805 | case Instruction::Mul: | |||
| 4806 | case Instruction::UDiv: | |||
| 4807 | case Instruction::URem: | |||
| 4808 | case Instruction::And: | |||
| 4809 | case Instruction::Or: | |||
| 4810 | case Instruction::AShr: | |||
| 4811 | case Instruction::Shl: | |||
| 4812 | return BinaryOp(Op); | |||
| 4813 | ||||
| 4814 | case Instruction::Xor: | |||
| 4815 | if (auto *RHSC = dyn_cast<ConstantInt>(Op->getOperand(1))) | |||
| 4816 | // If the RHS of the xor is a signmask, then this is just an add. | |||
| 4817 | // Instcombine turns add of signmask into xor as a strength reduction step. | |||
| 4818 | if (RHSC->getValue().isSignMask()) | |||
| 4819 | return BinaryOp(Instruction::Add, Op->getOperand(0), Op->getOperand(1)); | |||
| 4820 | return BinaryOp(Op); | |||
| 4821 | ||||
| 4822 | case Instruction::LShr: | |||
| 4823 | // Turn logical shift right of a constant into a unsigned divide. | |||
| 4824 | if (ConstantInt *SA = dyn_cast<ConstantInt>(Op->getOperand(1))) { | |||
| 4825 | uint32_t BitWidth = cast<IntegerType>(Op->getType())->getBitWidth(); | |||
| 4826 | ||||
| 4827 | // If the shift count is not less than the bitwidth, the result of | |||
| 4828 | // the shift is undefined. Don't try to analyze it, because the | |||
| 4829 | // resolution chosen here may differ from the resolution chosen in | |||
| 4830 | // other parts of the compiler. | |||
| 4831 | if (SA->getValue().ult(BitWidth)) { | |||
| 4832 | Constant *X = | |||
| 4833 | ConstantInt::get(SA->getContext(), | |||
| 4834 | APInt::getOneBitSet(BitWidth, SA->getZExtValue())); | |||
| 4835 | return BinaryOp(Instruction::UDiv, Op->getOperand(0), X); | |||
| 4836 | } | |||
| 4837 | } | |||
| 4838 | return BinaryOp(Op); | |||
| 4839 | ||||
| 4840 | case Instruction::ExtractValue: { | |||
| 4841 | auto *EVI = cast<ExtractValueInst>(Op); | |||
| 4842 | if (EVI->getNumIndices() != 1 || EVI->getIndices()[0] != 0) | |||
| 4843 | break; | |||
| 4844 | ||||
| 4845 | auto *WO = dyn_cast<WithOverflowInst>(EVI->getAggregateOperand()); | |||
| 4846 | if (!WO) | |||
| 4847 | break; | |||
| 4848 | ||||
| 4849 | Instruction::BinaryOps BinOp = WO->getBinaryOp(); | |||
| 4850 | bool Signed = WO->isSigned(); | |||
| 4851 | // TODO: Should add nuw/nsw flags for mul as well. | |||
| 4852 | if (BinOp == Instruction::Mul || !isOverflowIntrinsicNoWrap(WO, DT)) | |||
| 4853 | return BinaryOp(BinOp, WO->getLHS(), WO->getRHS()); | |||
| 4854 | ||||
| 4855 | // Now that we know that all uses of the arithmetic-result component of | |||
| 4856 | // CI are guarded by the overflow check, we can go ahead and pretend | |||
| 4857 | // that the arithmetic is non-overflowing. | |||
| 4858 | return BinaryOp(BinOp, WO->getLHS(), WO->getRHS(), | |||
| 4859 | /* IsNSW = */ Signed, /* IsNUW = */ !Signed); | |||
| 4860 | } | |||
| 4861 | ||||
| 4862 | default: | |||
| 4863 | break; | |||
| 4864 | } | |||
| 4865 | ||||
| 4866 | // Recognise intrinsic loop.decrement.reg, and as this has exactly the same | |||
| 4867 | // semantics as a Sub, return a binary sub expression. | |||
| 4868 | if (auto *II = dyn_cast<IntrinsicInst>(V)) | |||
| 4869 | if (II->getIntrinsicID() == Intrinsic::loop_decrement_reg) | |||
| 4870 | return BinaryOp(Instruction::Sub, II->getOperand(0), II->getOperand(1)); | |||
| 4871 | ||||
| 4872 | return None; | |||
| 4873 | } | |||
| 4874 | ||||
| 4875 | /// Helper function to createAddRecFromPHIWithCasts. We have a phi | |||
| 4876 | /// node whose symbolic (unknown) SCEV is \p SymbolicPHI, which is updated via | |||
| 4877 | /// the loop backedge by a SCEVAddExpr, possibly also with a few casts on the | |||
| 4878 | /// way. This function checks if \p Op, an operand of this SCEVAddExpr, | |||
| 4879 | /// follows one of the following patterns: | |||
| 4880 | /// Op == (SExt ix (Trunc iy (%SymbolicPHI) to ix) to iy) | |||
| 4881 | /// Op == (ZExt ix (Trunc iy (%SymbolicPHI) to ix) to iy) | |||
| 4882 | /// If the SCEV expression of \p Op conforms with one of the expected patterns | |||
| 4883 | /// we return the type of the truncation operation, and indicate whether the | |||
| 4884 | /// truncated type should be treated as signed/unsigned by setting | |||
| 4885 | /// \p Signed to true/false, respectively. | |||
| 4886 | static Type *isSimpleCastedPHI(const SCEV *Op, const SCEVUnknown *SymbolicPHI, | |||
| 4887 | bool &Signed, ScalarEvolution &SE) { | |||
| 4888 | // The case where Op == SymbolicPHI (that is, with no type conversions on | |||
| 4889 | // the way) is handled by the regular add recurrence creating logic and | |||
| 4890 | // would have already been triggered in createAddRecForPHI. Reaching it here | |||
| 4891 | // means that createAddRecFromPHI had failed for this PHI before (e.g., | |||
| 4892 | // because one of the other operands of the SCEVAddExpr updating this PHI is | |||
| 4893 | // not invariant). | |||
| 4894 | // | |||
| 4895 | // Here we look for the case where Op = (ext(trunc(SymbolicPHI))), and in | |||
| 4896 | // this case predicates that allow us to prove that Op == SymbolicPHI will | |||
| 4897 | // be added. | |||
| 4898 | if (Op == SymbolicPHI) | |||
| 4899 | return nullptr; | |||
| 4900 | ||||
| 4901 | unsigned SourceBits = SE.getTypeSizeInBits(SymbolicPHI->getType()); | |||
| 4902 | unsigned NewBits = SE.getTypeSizeInBits(Op->getType()); | |||
| 4903 | if (SourceBits != NewBits) | |||
| 4904 | return nullptr; | |||
| 4905 | ||||
| 4906 | const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(Op); | |||
| 4907 | const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(Op); | |||
| 4908 | if (!SExt && !ZExt) | |||
| 4909 | return nullptr; | |||
| 4910 | const SCEVTruncateExpr *Trunc = | |||
| 4911 | SExt ? dyn_cast<SCEVTruncateExpr>(SExt->getOperand()) | |||
| 4912 | : dyn_cast<SCEVTruncateExpr>(ZExt->getOperand()); | |||
| 4913 | if (!Trunc) | |||
| 4914 | return nullptr; | |||
| 4915 | const SCEV *X = Trunc->getOperand(); | |||
| 4916 | if (X != SymbolicPHI) | |||
| 4917 | return nullptr; | |||
| 4918 | Signed = SExt != nullptr; | |||
| 4919 | return Trunc->getType(); | |||
| 4920 | } | |||
| 4921 | ||||
| 4922 | static const Loop *isIntegerLoopHeaderPHI(const PHINode *PN, LoopInfo &LI) { | |||
| 4923 | if (!PN->getType()->isIntegerTy()) | |||
| 4924 | return nullptr; | |||
| 4925 | const Loop *L = LI.getLoopFor(PN->getParent()); | |||
| 4926 | if (!L || L->getHeader() != PN->getParent()) | |||
| 4927 | return nullptr; | |||
| 4928 | return L; | |||
| 4929 | } | |||
| 4930 | ||||
| 4931 | // Analyze \p SymbolicPHI, a SCEV expression of a phi node, and check if the | |||
| 4932 | // computation that updates the phi follows the following pattern: | |||
| 4933 | // (SExt/ZExt ix (Trunc iy (%SymbolicPHI) to ix) to iy) + InvariantAccum | |||
| 4934 | // which correspond to a phi->trunc->sext/zext->add->phi update chain. | |||
| 4935 | // If so, try to see if it can be rewritten as an AddRecExpr under some | |||
| 4936 | // Predicates. If successful, return them as a pair. Also cache the results | |||
| 4937 | // of the analysis. | |||
| 4938 | // | |||
| 4939 | // Example usage scenario: | |||
| 4940 | // Say the Rewriter is called for the following SCEV: | |||
| 4941 | // 8 * ((sext i32 (trunc i64 %X to i32) to i64) + %Step) | |||
| 4942 | // where: | |||
| 4943 | // %X = phi i64 (%Start, %BEValue) | |||
| 4944 | // It will visitMul->visitAdd->visitSExt->visitTrunc->visitUnknown(%X), | |||
| 4945 | // and call this function with %SymbolicPHI = %X. | |||
| 4946 | // | |||
| 4947 | // The analysis will find that the value coming around the backedge has | |||
| 4948 | // the following SCEV: | |||
| 4949 | // BEValue = ((sext i32 (trunc i64 %X to i32) to i64) + %Step) | |||
| 4950 | // Upon concluding that this matches the desired pattern, the function | |||
| 4951 | // will return the pair {NewAddRec, SmallPredsVec} where: | |||
| 4952 | // NewAddRec = {%Start,+,%Step} | |||
| 4953 | // SmallPredsVec = {P1, P2, P3} as follows: | |||
| 4954 | // P1(WrapPred): AR: {trunc(%Start),+,(trunc %Step)}<nsw> Flags: <nssw> | |||
| 4955 | // P2(EqualPred): %Start == (sext i32 (trunc i64 %Start to i32) to i64) | |||
| 4956 | // P3(EqualPred): %Step == (sext i32 (trunc i64 %Step to i32) to i64) | |||
| 4957 | // The returned pair means that SymbolicPHI can be rewritten into NewAddRec | |||
| 4958 | // under the predicates {P1,P2,P3}. | |||
| 4959 | // This predicated rewrite will be cached in PredicatedSCEVRewrites: | |||
| 4960 | // PredicatedSCEVRewrites[{%X,L}] = {NewAddRec, {P1,P2,P3)} | |||
| 4961 | // | |||
| 4962 | // TODO's: | |||
| 4963 | // | |||
| 4964 | // 1) Extend the Induction descriptor to also support inductions that involve | |||
| 4965 | // casts: When needed (namely, when we are called in the context of the | |||
| 4966 | // vectorizer induction analysis), a Set of cast instructions will be | |||
| 4967 | // populated by this method, and provided back to isInductionPHI. This is | |||
| 4968 | // needed to allow the vectorizer to properly record them to be ignored by | |||
| 4969 | // the cost model and to avoid vectorizing them (otherwise these casts, | |||
| 4970 | // which are redundant under the runtime overflow checks, will be | |||
| 4971 | // vectorized, which can be costly). | |||
| 4972 | // | |||
| 4973 | // 2) Support additional induction/PHISCEV patterns: We also want to support | |||
| 4974 | // inductions where the sext-trunc / zext-trunc operations (partly) occur | |||
| 4975 | // after the induction update operation (the induction increment): | |||
| 4976 | // | |||
| 4977 | // (Trunc iy (SExt/ZExt ix (%SymbolicPHI + InvariantAccum) to iy) to ix) | |||
| 4978 | // which correspond to a phi->add->trunc->sext/zext->phi update chain. | |||
| 4979 | // | |||
| 4980 | // (Trunc iy ((SExt/ZExt ix (%SymbolicPhi) to iy) + InvariantAccum) to ix) | |||
| 4981 | // which correspond to a phi->trunc->add->sext/zext->phi update chain. | |||
| 4982 | // | |||
| 4983 | // 3) Outline common code with createAddRecFromPHI to avoid duplication. | |||
| 4984 | Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>> | |||
| 4985 | ScalarEvolution::createAddRecFromPHIWithCastsImpl(const SCEVUnknown *SymbolicPHI) { | |||
| 4986 | SmallVector<const SCEVPredicate *, 3> Predicates; | |||
| 4987 | ||||
| 4988 | // *** Part1: Analyze if we have a phi-with-cast pattern for which we can | |||
| 4989 | // return an AddRec expression under some predicate. | |||
| 4990 | ||||
| 4991 | auto *PN = cast<PHINode>(SymbolicPHI->getValue()); | |||
| 4992 | const Loop *L = isIntegerLoopHeaderPHI(PN, LI); | |||
| 4993 | assert(L && "Expecting an integer loop header phi")((void)0); | |||
| 4994 | ||||
| 4995 | // The loop may have multiple entrances or multiple exits; we can analyze | |||
| 4996 | // this phi as an addrec if it has a unique entry value and a unique | |||
| 4997 | // backedge value. | |||
| 4998 | Value *BEValueV = nullptr, *StartValueV = nullptr; | |||
| 4999 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { | |||
| 5000 | Value *V = PN->getIncomingValue(i); | |||
| 5001 | if (L->contains(PN->getIncomingBlock(i))) { | |||
| 5002 | if (!BEValueV) { | |||
| 5003 | BEValueV = V; | |||
| 5004 | } else if (BEValueV != V) { | |||
| 5005 | BEValueV = nullptr; | |||
| 5006 | break; | |||
| 5007 | } | |||
| 5008 | } else if (!StartValueV) { | |||
| 5009 | StartValueV = V; | |||
| 5010 | } else if (StartValueV != V) { | |||
| 5011 | StartValueV = nullptr; | |||
| 5012 | break; | |||
| 5013 | } | |||
| 5014 | } | |||
| 5015 | if (!BEValueV || !StartValueV) | |||
| 5016 | return None; | |||
| 5017 | ||||
| 5018 | const SCEV *BEValue = getSCEV(BEValueV); | |||
| 5019 | ||||
| 5020 | // If the value coming around the backedge is an add with the symbolic | |||
| 5021 | // value we just inserted, possibly with casts that we can ignore under | |||
| 5022 | // an appropriate runtime guard, then we found a simple induction variable! | |||
| 5023 | const auto *Add = dyn_cast<SCEVAddExpr>(BEValue); | |||
| 5024 | if (!Add) | |||
| 5025 | return None; | |||
| 5026 | ||||
| 5027 | // If there is a single occurrence of the symbolic value, possibly | |||
| 5028 | // casted, replace it with a recurrence. | |||
| 5029 | unsigned FoundIndex = Add->getNumOperands(); | |||
| 5030 | Type *TruncTy = nullptr; | |||
| 5031 | bool Signed; | |||
| 5032 | for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) | |||
| 5033 | if ((TruncTy = | |||
| 5034 | isSimpleCastedPHI(Add->getOperand(i), SymbolicPHI, Signed, *this))) | |||
| 5035 | if (FoundIndex == e) { | |||
| 5036 | FoundIndex = i; | |||
| 5037 | break; | |||
| 5038 | } | |||
| 5039 | ||||
| 5040 | if (FoundIndex == Add->getNumOperands()) | |||
| 5041 | return None; | |||
| 5042 | ||||
| 5043 | // Create an add with everything but the specified operand. | |||
| 5044 | SmallVector<const SCEV *, 8> Ops; | |||
| 5045 | for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) | |||
| 5046 | if (i != FoundIndex) | |||
| 5047 | Ops.push_back(Add->getOperand(i)); | |||
| 5048 | const SCEV *Accum = getAddExpr(Ops); | |||
| 5049 | ||||
| 5050 | // The runtime checks will not be valid if the step amount is | |||
| 5051 | // varying inside the loop. | |||
| 5052 | if (!isLoopInvariant(Accum, L)) | |||
| 5053 | return None; | |||
| 5054 | ||||
| 5055 | // *** Part2: Create the predicates | |||
| 5056 | ||||
| 5057 | // Analysis was successful: we have a phi-with-cast pattern for which we | |||
| 5058 | // can return an AddRec expression under the following predicates: | |||
| 5059 | // | |||
| 5060 | // P1: A Wrap predicate that guarantees that Trunc(Start) + i*Trunc(Accum) | |||
| 5061 | // fits within the truncated type (does not overflow) for i = 0 to n-1. | |||
| 5062 | // P2: An Equal predicate that guarantees that | |||
| 5063 | // Start = (Ext ix (Trunc iy (Start) to ix) to iy) | |||
| 5064 | // P3: An Equal predicate that guarantees that | |||
| 5065 | // Accum = (Ext ix (Trunc iy (Accum) to ix) to iy) | |||
| 5066 | // | |||
| 5067 | // As we next prove, the above predicates guarantee that: | |||
| 5068 | // Start + i*Accum = (Ext ix (Trunc iy ( Start + i*Accum ) to ix) to iy) | |||
| 5069 | // | |||
| 5070 | // | |||
| 5071 | // More formally, we want to prove that: | |||
| 5072 | // Expr(i+1) = Start + (i+1) * Accum | |||
| 5073 | // = (Ext ix (Trunc iy (Expr(i)) to ix) to iy) + Accum | |||
| 5074 | // | |||
| 5075 | // Given that: | |||
| 5076 | // 1) Expr(0) = Start | |||
| 5077 | // 2) Expr(1) = Start + Accum | |||
| 5078 | // = (Ext ix (Trunc iy (Start) to ix) to iy) + Accum :: from P2 | |||
| 5079 | // 3) Induction hypothesis (step i): | |||
| 5080 | // Expr(i) = (Ext ix (Trunc iy (Expr(i-1)) to ix) to iy) + Accum | |||
| 5081 | // | |||
| 5082 | // Proof: | |||
| 5083 | // Expr(i+1) = | |||
| 5084 | // = Start + (i+1)*Accum | |||
| 5085 | // = (Start + i*Accum) + Accum | |||
| 5086 | // = Expr(i) + Accum | |||
| 5087 | // = (Ext ix (Trunc iy (Expr(i-1)) to ix) to iy) + Accum + Accum | |||
| 5088 | // :: from step i | |||
| 5089 | // | |||
| 5090 | // = (Ext ix (Trunc iy (Start + (i-1)*Accum) to ix) to iy) + Accum + Accum | |||
| 5091 | // | |||
| 5092 | // = (Ext ix (Trunc iy (Start + (i-1)*Accum) to ix) to iy) | |||
| 5093 | // + (Ext ix (Trunc iy (Accum) to ix) to iy) | |||
| 5094 | // + Accum :: from P3 | |||
| 5095 | // | |||
| 5096 | // = (Ext ix (Trunc iy ((Start + (i-1)*Accum) + Accum) to ix) to iy) | |||
| 5097 | // + Accum :: from P1: Ext(x)+Ext(y)=>Ext(x+y) | |||
| 5098 | // | |||
| 5099 | // = (Ext ix (Trunc iy (Start + i*Accum) to ix) to iy) + Accum | |||
| 5100 | // = (Ext ix (Trunc iy (Expr(i)) to ix) to iy) + Accum | |||
| 5101 | // | |||
| 5102 | // By induction, the same applies to all iterations 1<=i<n: | |||
| 5103 | // | |||
| 5104 | ||||
| 5105 | // Create a truncated addrec for which we will add a no overflow check (P1). | |||
| 5106 | const SCEV *StartVal = getSCEV(StartValueV); | |||
| 5107 | const SCEV *PHISCEV = | |||
| 5108 | getAddRecExpr(getTruncateExpr(StartVal, TruncTy), | |||
| 5109 | getTruncateExpr(Accum, TruncTy), L, SCEV::FlagAnyWrap); | |||
| 5110 | ||||
| 5111 | // PHISCEV can be either a SCEVConstant or a SCEVAddRecExpr. | |||
| 5112 | // ex: If truncated Accum is 0 and StartVal is a constant, then PHISCEV | |||
| 5113 | // will be constant. | |||
| 5114 | // | |||
| 5115 | // If PHISCEV is a constant, then P1 degenerates into P2 or P3, so we don't | |||
| 5116 | // add P1. | |||
| 5117 | if (const auto *AR = dyn_cast<SCEVAddRecExpr>(PHISCEV)) { | |||
| 5118 | SCEVWrapPredicate::IncrementWrapFlags AddedFlags = | |||
| 5119 | Signed ? SCEVWrapPredicate::IncrementNSSW | |||
| 5120 | : SCEVWrapPredicate::IncrementNUSW; | |||
| 5121 | const SCEVPredicate *AddRecPred = getWrapPredicate(AR, AddedFlags); | |||
| 5122 | Predicates.push_back(AddRecPred); | |||
| 5123 | } | |||
| 5124 | ||||
| 5125 | // Create the Equal Predicates P2,P3: | |||
| 5126 | ||||
| 5127 | // It is possible that the predicates P2 and/or P3 are computable at | |||
| 5128 | // compile time due to StartVal and/or Accum being constants. | |||
| 5129 | // If either one is, then we can check that now and escape if either P2 | |||
| 5130 | // or P3 is false. | |||
| 5131 | ||||
| 5132 | // Construct the extended SCEV: (Ext ix (Trunc iy (Expr) to ix) to iy) | |||
| 5133 | // for each of StartVal and Accum | |||
| 5134 | auto getExtendedExpr = [&](const SCEV *Expr, | |||
| 5135 | bool CreateSignExtend) -> const SCEV * { | |||
| 5136 | assert(isLoopInvariant(Expr, L) && "Expr is expected to be invariant")((void)0); | |||
| 5137 | const SCEV *TruncatedExpr = getTruncateExpr(Expr, TruncTy); | |||
| 5138 | const SCEV *ExtendedExpr = | |||
| 5139 | CreateSignExtend ? getSignExtendExpr(TruncatedExpr, Expr->getType()) | |||
| 5140 | : getZeroExtendExpr(TruncatedExpr, Expr->getType()); | |||
| 5141 | return ExtendedExpr; | |||
| 5142 | }; | |||
| 5143 | ||||
| 5144 | // Given: | |||
| 5145 | // ExtendedExpr = (Ext ix (Trunc iy (Expr) to ix) to iy | |||
| 5146 | // = getExtendedExpr(Expr) | |||
| 5147 | // Determine whether the predicate P: Expr == ExtendedExpr | |||
| 5148 | // is known to be false at compile time | |||
| 5149 | auto PredIsKnownFalse = [&](const SCEV *Expr, | |||
| 5150 | const SCEV *ExtendedExpr) -> bool { | |||
| 5151 | return Expr != ExtendedExpr && | |||
| 5152 | isKnownPredicate(ICmpInst::ICMP_NE, Expr, ExtendedExpr); | |||
| 5153 | }; | |||
| 5154 | ||||
| 5155 | const SCEV *StartExtended = getExtendedExpr(StartVal, Signed); | |||
| 5156 | if (PredIsKnownFalse(StartVal, StartExtended)) { | |||
| 5157 | LLVM_DEBUG(dbgs() << "P2 is compile-time false\n";)do { } while (false); | |||
| 5158 | return None; | |||
| 5159 | } | |||
| 5160 | ||||
| 5161 | // The Step is always Signed (because the overflow checks are either | |||
| 5162 | // NSSW or NUSW) | |||
| 5163 | const SCEV *AccumExtended = getExtendedExpr(Accum, /*CreateSignExtend=*/true); | |||
| 5164 | if (PredIsKnownFalse(Accum, AccumExtended)) { | |||
| 5165 | LLVM_DEBUG(dbgs() << "P3 is compile-time false\n";)do { } while (false); | |||
| 5166 | return None; | |||
| 5167 | } | |||
| 5168 | ||||
| 5169 | auto AppendPredicate = [&](const SCEV *Expr, | |||
| 5170 | const SCEV *ExtendedExpr) -> void { | |||
| 5171 | if (Expr != ExtendedExpr && | |||
| 5172 | !isKnownPredicate(ICmpInst::ICMP_EQ, Expr, ExtendedExpr)) { | |||
| 5173 | const SCEVPredicate *Pred = getEqualPredicate(Expr, ExtendedExpr); | |||
| 5174 | LLVM_DEBUG(dbgs() << "Added Predicate: " << *Pred)do { } while (false); | |||
| 5175 | Predicates.push_back(Pred); | |||
| 5176 | } | |||
| 5177 | }; | |||
| 5178 | ||||
| 5179 | AppendPredicate(StartVal, StartExtended); | |||
| 5180 | AppendPredicate(Accum, AccumExtended); | |||
| 5181 | ||||
| 5182 | // *** Part3: Predicates are ready. Now go ahead and create the new addrec in | |||
| 5183 | // which the casts had been folded away. The caller can rewrite SymbolicPHI | |||
| 5184 | // into NewAR if it will also add the runtime overflow checks specified in | |||
| 5185 | // Predicates. | |||
| 5186 | auto *NewAR = getAddRecExpr(StartVal, Accum, L, SCEV::FlagAnyWrap); | |||
| 5187 | ||||
| 5188 | std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>> PredRewrite = | |||
| 5189 | std::make_pair(NewAR, Predicates); | |||
| 5190 | // Remember the result of the analysis for this SCEV at this locayyytion. | |||
| 5191 | PredicatedSCEVRewrites[{SymbolicPHI, L}] = PredRewrite; | |||
| 5192 | return PredRewrite; | |||
| 5193 | } | |||
| 5194 | ||||
| 5195 | Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>> | |||
| 5196 | ScalarEvolution::createAddRecFromPHIWithCasts(const SCEVUnknown *SymbolicPHI) { | |||
| 5197 | auto *PN = cast<PHINode>(SymbolicPHI->getValue()); | |||
| 5198 | const Loop *L = isIntegerLoopHeaderPHI(PN, LI); | |||
| 5199 | if (!L) | |||
| 5200 | return None; | |||
| 5201 | ||||
| 5202 | // Check to see if we already analyzed this PHI. | |||
| 5203 | auto I = PredicatedSCEVRewrites.find({SymbolicPHI, L}); | |||
| 5204 | if (I != PredicatedSCEVRewrites.end()) { | |||
| 5205 | std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>> Rewrite = | |||
| 5206 | I->second; | |||
| 5207 | // Analysis was done before and failed to create an AddRec: | |||
| 5208 | if (Rewrite.first == SymbolicPHI) | |||
| 5209 | return None; | |||
| 5210 | // Analysis was done before and succeeded to create an AddRec under | |||
| 5211 | // a predicate: | |||
| 5212 | assert(isa<SCEVAddRecExpr>(Rewrite.first) && "Expected an AddRec")((void)0); | |||
| 5213 | assert(!(Rewrite.second).empty() && "Expected to find Predicates")((void)0); | |||
| 5214 | return Rewrite; | |||
| 5215 | } | |||
| 5216 | ||||
| 5217 | Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>> | |||
| 5218 | Rewrite = createAddRecFromPHIWithCastsImpl(SymbolicPHI); | |||
| 5219 | ||||
| 5220 | // Record in the cache that the analysis failed | |||
| 5221 | if (!Rewrite) { | |||
| 5222 | SmallVector<const SCEVPredicate *, 3> Predicates; | |||
| 5223 | PredicatedSCEVRewrites[{SymbolicPHI, L}] = {SymbolicPHI, Predicates}; | |||
| 5224 | return None; | |||
| 5225 | } | |||
| 5226 | ||||
| 5227 | return Rewrite; | |||
| 5228 | } | |||
| 5229 | ||||
| 5230 | // FIXME: This utility is currently required because the Rewriter currently | |||
| 5231 | // does not rewrite this expression: | |||
| 5232 | // {0, +, (sext ix (trunc iy to ix) to iy)} | |||
| 5233 | // into {0, +, %step}, | |||
| 5234 | // even when the following Equal predicate exists: | |||
| 5235 | // "%step == (sext ix (trunc iy to ix) to iy)". | |||
| 5236 | bool PredicatedScalarEvolution::areAddRecsEqualWithPreds( | |||
| 5237 | const SCEVAddRecExpr *AR1, const SCEVAddRecExpr *AR2) const { | |||
| 5238 | if (AR1 == AR2) | |||
| 5239 | return true; | |||
| 5240 | ||||
| 5241 | auto areExprsEqual = [&](const SCEV *Expr1, const SCEV *Expr2) -> bool { | |||
| 5242 | if (Expr1 != Expr2 && !Preds.implies(SE.getEqualPredicate(Expr1, Expr2)) && | |||
| 5243 | !Preds.implies(SE.getEqualPredicate(Expr2, Expr1))) | |||
| 5244 | return false; | |||
| 5245 | return true; | |||
| 5246 | }; | |||
| 5247 | ||||
| 5248 | if (!areExprsEqual(AR1->getStart(), AR2->getStart()) || | |||
| 5249 | !areExprsEqual(AR1->getStepRecurrence(SE), AR2->getStepRecurrence(SE))) | |||
| 5250 | return false; | |||
| 5251 | return true; | |||
| 5252 | } | |||
| 5253 | ||||
| 5254 | /// A helper function for createAddRecFromPHI to handle simple cases. | |||
| 5255 | /// | |||
| 5256 | /// This function tries to find an AddRec expression for the simplest (yet most | |||
| 5257 | /// common) cases: PN = PHI(Start, OP(Self, LoopInvariant)). | |||
| 5258 | /// If it fails, createAddRecFromPHI will use a more general, but slow, | |||
| 5259 | /// technique for finding the AddRec expression. | |||
| 5260 | const SCEV *ScalarEvolution::createSimpleAffineAddRec(PHINode *PN, | |||
| 5261 | Value *BEValueV, | |||
| 5262 | Value *StartValueV) { | |||
| 5263 | const Loop *L = LI.getLoopFor(PN->getParent()); | |||
| 5264 | assert(L && L->getHeader() == PN->getParent())((void)0); | |||
| 5265 | assert(BEValueV && StartValueV)((void)0); | |||
| 5266 | ||||
| 5267 | auto BO = MatchBinaryOp(BEValueV, DT); | |||
| 5268 | if (!BO) | |||
| 5269 | return nullptr; | |||
| 5270 | ||||
| 5271 | if (BO->Opcode != Instruction::Add) | |||
| 5272 | return nullptr; | |||
| 5273 | ||||
| 5274 | const SCEV *Accum = nullptr; | |||
| 5275 | if (BO->LHS == PN && L->isLoopInvariant(BO->RHS)) | |||
| 5276 | Accum = getSCEV(BO->RHS); | |||
| 5277 | else if (BO->RHS == PN && L->isLoopInvariant(BO->LHS)) | |||
| 5278 | Accum = getSCEV(BO->LHS); | |||
| 5279 | ||||
| 5280 | if (!Accum) | |||
| 5281 | return nullptr; | |||
| 5282 | ||||
| 5283 | SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; | |||
| 5284 | if (BO->IsNUW) | |||
| 5285 | Flags = setFlags(Flags, SCEV::FlagNUW); | |||
| 5286 | if (BO->IsNSW) | |||
| 5287 | Flags = setFlags(Flags, SCEV::FlagNSW); | |||
| 5288 | ||||
| 5289 | const SCEV *StartVal = getSCEV(StartValueV); | |||
| 5290 | const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags); | |||
| 5291 | ||||
| 5292 | ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV; | |||
| 5293 | ||||
| 5294 | // We can add Flags to the post-inc expression only if we | |||
| 5295 | // know that it is *undefined behavior* for BEValueV to | |||
| 5296 | // overflow. | |||
| 5297 | if (auto *BEInst = dyn_cast<Instruction>(BEValueV)) | |||
| 5298 | if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L)) | |||
| 5299 | (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags); | |||
| 5300 | ||||
| 5301 | return PHISCEV; | |||
| 5302 | } | |||
| 5303 | ||||
| 5304 | const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) { | |||
| 5305 | const Loop *L = LI.getLoopFor(PN->getParent()); | |||
| 5306 | if (!L || L->getHeader() != PN->getParent()) | |||
| 5307 | return nullptr; | |||
| 5308 | ||||
| 5309 | // The loop may have multiple entrances or multiple exits; we can analyze | |||
| 5310 | // this phi as an addrec if it has a unique entry value and a unique | |||
| 5311 | // backedge value. | |||
| 5312 | Value *BEValueV = nullptr, *StartValueV = nullptr; | |||
| 5313 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { | |||
| 5314 | Value *V = PN->getIncomingValue(i); | |||
| 5315 | if (L->contains(PN->getIncomingBlock(i))) { | |||
| 5316 | if (!BEValueV) { | |||
| 5317 | BEValueV = V; | |||
| 5318 | } else if (BEValueV != V) { | |||
| 5319 | BEValueV = nullptr; | |||
| 5320 | break; | |||
| 5321 | } | |||
| 5322 | } else if (!StartValueV) { | |||
| 5323 | StartValueV = V; | |||
| 5324 | } else if (StartValueV != V) { | |||
| 5325 | StartValueV = nullptr; | |||
| 5326 | break; | |||
| 5327 | } | |||
| 5328 | } | |||
| 5329 | if (!BEValueV || !StartValueV) | |||
| 5330 | return nullptr; | |||
| 5331 | ||||
| 5332 | assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&((void)0) | |||
| 5333 | "PHI node already processed?")((void)0); | |||
| 5334 | ||||
| 5335 | // First, try to find AddRec expression without creating a fictituos symbolic | |||
| 5336 | // value for PN. | |||
| 5337 | if (auto *S = createSimpleAffineAddRec(PN, BEValueV, StartValueV)) | |||
| 5338 | return S; | |||
| 5339 | ||||
| 5340 | // Handle PHI node value symbolically. | |||
| 5341 | const SCEV *SymbolicName = getUnknown(PN); | |||
| 5342 | ValueExprMap.insert({SCEVCallbackVH(PN, this), SymbolicName}); | |||
| 5343 | ||||
| 5344 | // Using this symbolic name for the PHI, analyze the value coming around | |||
| 5345 | // the back-edge. | |||
| 5346 | const SCEV *BEValue = getSCEV(BEValueV); | |||
| 5347 | ||||
| 5348 | // NOTE: If BEValue is loop invariant, we know that the PHI node just | |||
| 5349 | // has a special value for the first iteration of the loop. | |||
| 5350 | ||||
| 5351 | // If the value coming around the backedge is an add with the symbolic | |||
| 5352 | // value we just inserted, then we found a simple induction variable! | |||
| 5353 | if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) { | |||
| 5354 | // If there is a single occurrence of the symbolic value, replace it | |||
| 5355 | // with a recurrence. | |||
| 5356 | unsigned FoundIndex = Add->getNumOperands(); | |||
| 5357 | for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) | |||
| 5358 | if (Add->getOperand(i) == SymbolicName) | |||
| 5359 | if (FoundIndex == e) { | |||
| 5360 | FoundIndex = i; | |||
| 5361 | break; | |||
| 5362 | } | |||
| 5363 | ||||
| 5364 | if (FoundIndex != Add->getNumOperands()) { | |||
| 5365 | // Create an add with everything but the specified operand. | |||
| 5366 | SmallVector<const SCEV *, 8> Ops; | |||
| 5367 | for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) | |||
| 5368 | if (i != FoundIndex) | |||
| 5369 | Ops.push_back(SCEVBackedgeConditionFolder::rewrite(Add->getOperand(i), | |||
| 5370 | L, *this)); | |||
| 5371 | const SCEV *Accum = getAddExpr(Ops); | |||
| 5372 | ||||
| 5373 | // This is not a valid addrec if the step amount is varying each | |||
| 5374 | // loop iteration, but is not itself an addrec in this loop. | |||
| 5375 | if (isLoopInvariant(Accum, L) || | |||
| 5376 | (isa<SCEVAddRecExpr>(Accum) && | |||
| 5377 | cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) { | |||
| 5378 | SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; | |||
| 5379 | ||||
| 5380 | if (auto BO = MatchBinaryOp(BEValueV, DT)) { | |||
| 5381 | if (BO->Opcode == Instruction::Add && BO->LHS == PN) { | |||
| 5382 | if (BO->IsNUW) | |||
| 5383 | Flags = setFlags(Flags, SCEV::FlagNUW); | |||
| 5384 | if (BO->IsNSW) | |||
| 5385 | Flags = setFlags(Flags, SCEV::FlagNSW); | |||
| 5386 | } | |||
| 5387 | } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) { | |||
| 5388 | // If the increment is an inbounds GEP, then we know the address | |||
| 5389 | // space cannot be wrapped around. We cannot make any guarantee | |||
| 5390 | // about signed or unsigned overflow because pointers are | |||
| 5391 | // unsigned but we may have a negative index from the base | |||
| 5392 | // pointer. We can guarantee that no unsigned wrap occurs if the | |||
| 5393 | // indices form a positive value. | |||
| 5394 | if (GEP->isInBounds() && GEP->getOperand(0) == PN) { | |||
| 5395 | Flags = setFlags(Flags, SCEV::FlagNW); | |||
| 5396 | ||||
| 5397 | const SCEV *Ptr = getSCEV(GEP->getPointerOperand()); | |||
| 5398 | if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr))) | |||
| 5399 | Flags = setFlags(Flags, SCEV::FlagNUW); | |||
| 5400 | } | |||
| 5401 | ||||
| 5402 | // We cannot transfer nuw and nsw flags from subtraction | |||
| 5403 | // operations -- sub nuw X, Y is not the same as add nuw X, -Y | |||
| 5404 | // for instance. | |||
| 5405 | } | |||
| 5406 | ||||
| 5407 | const SCEV *StartVal = getSCEV(StartValueV); | |||
| 5408 | const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags); | |||
| 5409 | ||||
| 5410 | // Okay, for the entire analysis of this edge we assumed the PHI | |||
| 5411 | // to be symbolic. We now need to go back and purge all of the | |||
| 5412 | // entries for the scalars that use the symbolic expression. | |||
| 5413 | forgetSymbolicName(PN, SymbolicName); | |||
| 5414 | ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV; | |||
| 5415 | ||||
| 5416 | // We can add Flags to the post-inc expression only if we | |||
| 5417 | // know that it is *undefined behavior* for BEValueV to | |||
| 5418 | // overflow. | |||
| 5419 | if (auto *BEInst = dyn_cast<Instruction>(BEValueV)) | |||
| 5420 | if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L)) | |||
| 5421 | (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags); | |||
| 5422 | ||||
| 5423 | return PHISCEV; | |||
| 5424 | } | |||
| 5425 | } | |||
| 5426 | } else { | |||
| 5427 | // Otherwise, this could be a loop like this: | |||
| 5428 | // i = 0; for (j = 1; ..; ++j) { .... i = j; } | |||
| 5429 | // In this case, j = {1,+,1} and BEValue is j. | |||
| 5430 | // Because the other in-value of i (0) fits the evolution of BEValue | |||
| 5431 | // i really is an addrec evolution. | |||
| 5432 | // | |||
| 5433 | // We can generalize this saying that i is the shifted value of BEValue | |||
| 5434 | // by one iteration: | |||
| 5435 | // PHI(f(0), f({1,+,1})) --> f({0,+,1}) | |||
| 5436 | const SCEV *Shifted = SCEVShiftRewriter::rewrite(BEValue, L, *this); | |||
| 5437 | const SCEV *Start = SCEVInitRewriter::rewrite(Shifted, L, *this, false); | |||
| 5438 | if (Shifted != getCouldNotCompute() && | |||
| 5439 | Start != getCouldNotCompute()) { | |||
| 5440 | const SCEV *StartVal = getSCEV(StartValueV); | |||
| 5441 | if (Start == StartVal) { | |||
| 5442 | // Okay, for the entire analysis of this edge we assumed the PHI | |||
| 5443 | // to be symbolic. We now need to go back and purge all of the | |||
| 5444 | // entries for the scalars that use the symbolic expression. | |||
| 5445 | forgetSymbolicName(PN, SymbolicName); | |||
| 5446 | ValueExprMap[SCEVCallbackVH(PN, this)] = Shifted; | |||
| 5447 | return Shifted; | |||
| 5448 | } | |||
| 5449 | } | |||
| 5450 | } | |||
| 5451 | ||||
| 5452 | // Remove the temporary PHI node SCEV that has been inserted while intending | |||
| 5453 | // to create an AddRecExpr for this PHI node. We can not keep this temporary | |||
| 5454 | // as it will prevent later (possibly simpler) SCEV expressions to be added | |||
| 5455 | // to the ValueExprMap. | |||
| 5456 | eraseValueFromMap(PN); | |||
| 5457 | ||||
| 5458 | return nullptr; | |||
| 5459 | } | |||
| 5460 | ||||
| 5461 | // Checks if the SCEV S is available at BB. S is considered available at BB | |||
| 5462 | // if S can be materialized at BB without introducing a fault. | |||
| 5463 | static bool IsAvailableOnEntry(const Loop *L, DominatorTree &DT, const SCEV *S, | |||
| 5464 | BasicBlock *BB) { | |||
| 5465 | struct CheckAvailable { | |||
| 5466 | bool TraversalDone = false; | |||
| 5467 | bool Available = true; | |||
| 5468 | ||||
| 5469 | const Loop *L = nullptr; // The loop BB is in (can be nullptr) | |||
| 5470 | BasicBlock *BB = nullptr; | |||
| 5471 | DominatorTree &DT; | |||
| 5472 | ||||
| 5473 | CheckAvailable(const Loop *L, BasicBlock *BB, DominatorTree &DT) | |||
| 5474 | : L(L), BB(BB), DT(DT) {} | |||
| 5475 | ||||
| 5476 | bool setUnavailable() { | |||
| 5477 | TraversalDone = true; | |||
| 5478 | Available = false; | |||
| 5479 | return false; | |||
| 5480 | } | |||
| 5481 | ||||
| 5482 | bool follow(const SCEV *S) { | |||
| 5483 | switch (S->getSCEVType()) { | |||
| 5484 | case scConstant: | |||
| 5485 | case scPtrToInt: | |||
| 5486 | case scTruncate: | |||
| 5487 | case scZeroExtend: | |||
| 5488 | case scSignExtend: | |||
| 5489 | case scAddExpr: | |||
| 5490 | case scMulExpr: | |||
| 5491 | case scUMaxExpr: | |||
| 5492 | case scSMaxExpr: | |||
| 5493 | case scUMinExpr: | |||
| 5494 | case scSMinExpr: | |||
| 5495 | // These expressions are available if their operand(s) is/are. | |||
| 5496 | return true; | |||
| 5497 | ||||
| 5498 | case scAddRecExpr: { | |||
| 5499 | // We allow add recurrences that are on the loop BB is in, or some | |||
| 5500 | // outer loop. This guarantees availability because the value of the | |||
| 5501 | // add recurrence at BB is simply the "current" value of the induction | |||
| 5502 | // variable. We can relax this in the future; for instance an add | |||
| 5503 | // recurrence on a sibling dominating loop is also available at BB. | |||
| 5504 | const auto *ARLoop = cast<SCEVAddRecExpr>(S)->getLoop(); | |||
| 5505 | if (L && (ARLoop == L || ARLoop->contains(L))) | |||
| 5506 | return true; | |||
| 5507 | ||||
| 5508 | return setUnavailable(); | |||
| 5509 | } | |||
| 5510 | ||||
| 5511 | case scUnknown: { | |||
| 5512 | // For SCEVUnknown, we check for simple dominance. | |||
| 5513 | const auto *SU = cast<SCEVUnknown>(S); | |||
| 5514 | Value *V = SU->getValue(); | |||
| 5515 | ||||
| 5516 | if (isa<Argument>(V)) | |||
| 5517 | return false; | |||
| 5518 | ||||
| 5519 | if (isa<Instruction>(V) && DT.dominates(cast<Instruction>(V), BB)) | |||
| 5520 | return false; | |||
| 5521 | ||||
| 5522 | return setUnavailable(); | |||
| 5523 | } | |||
| 5524 | ||||
| 5525 | case scUDivExpr: | |||
| 5526 | case scCouldNotCompute: | |||
| 5527 | // We do not try to smart about these at all. | |||
| 5528 | return setUnavailable(); | |||
| 5529 | } | |||
| 5530 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 5531 | } | |||
| 5532 | ||||
| 5533 | bool isDone() { return TraversalDone; } | |||
| 5534 | }; | |||
| 5535 | ||||
| 5536 | CheckAvailable CA(L, BB, DT); | |||
| 5537 | SCEVTraversal<CheckAvailable> ST(CA); | |||
| 5538 | ||||
| 5539 | ST.visitAll(S); | |||
| 5540 | return CA.Available; | |||
| 5541 | } | |||
| 5542 | ||||
| 5543 | // Try to match a control flow sequence that branches out at BI and merges back | |||
| 5544 | // at Merge into a "C ? LHS : RHS" select pattern. Return true on a successful | |||
| 5545 | // match. | |||
| 5546 | static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge, | |||
| 5547 | Value *&C, Value *&LHS, Value *&RHS) { | |||
| 5548 | C = BI->getCondition(); | |||
| 5549 | ||||
| 5550 | BasicBlockEdge LeftEdge(BI->getParent(), BI->getSuccessor(0)); | |||
| 5551 | BasicBlockEdge RightEdge(BI->getParent(), BI->getSuccessor(1)); | |||
| 5552 | ||||
| 5553 | if (!LeftEdge.isSingleEdge()) | |||
| 5554 | return false; | |||
| 5555 | ||||
| 5556 | assert(RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()")((void)0); | |||
| 5557 | ||||
| 5558 | Use &LeftUse = Merge->getOperandUse(0); | |||
| 5559 | Use &RightUse = Merge->getOperandUse(1); | |||
| 5560 | ||||
| 5561 | if (DT.dominates(LeftEdge, LeftUse) && DT.dominates(RightEdge, RightUse)) { | |||
| 5562 | LHS = LeftUse; | |||
| 5563 | RHS = RightUse; | |||
| 5564 | return true; | |||
| 5565 | } | |||
| 5566 | ||||
| 5567 | if (DT.dominates(LeftEdge, RightUse) && DT.dominates(RightEdge, LeftUse)) { | |||
| 5568 | LHS = RightUse; | |||
| 5569 | RHS = LeftUse; | |||
| 5570 | return true; | |||
| 5571 | } | |||
| 5572 | ||||
| 5573 | return false; | |||
| 5574 | } | |||
| 5575 | ||||
| 5576 | const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) { | |||
| 5577 | auto IsReachable = | |||
| 5578 | [&](BasicBlock *BB) { return DT.isReachableFromEntry(BB); }; | |||
| 5579 | if (PN->getNumIncomingValues() == 2 && all_of(PN->blocks(), IsReachable)) { | |||
| 5580 | const Loop *L = LI.getLoopFor(PN->getParent()); | |||
| 5581 | ||||
| 5582 | // We don't want to break LCSSA, even in a SCEV expression tree. | |||
| 5583 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) | |||
| 5584 | if (LI.getLoopFor(PN->getIncomingBlock(i)) != L) | |||
| 5585 | return nullptr; | |||
| 5586 | ||||
| 5587 | // Try to match | |||
| 5588 | // | |||
| 5589 | // br %cond, label %left, label %right | |||
| 5590 | // left: | |||
| 5591 | // br label %merge | |||
| 5592 | // right: | |||
| 5593 | // br label %merge | |||
| 5594 | // merge: | |||
| 5595 | // V = phi [ %x, %left ], [ %y, %right ] | |||
| 5596 | // | |||
| 5597 | // as "select %cond, %x, %y" | |||
| 5598 | ||||
| 5599 | BasicBlock *IDom = DT[PN->getParent()]->getIDom()->getBlock(); | |||
| 5600 | assert(IDom && "At least the entry block should dominate PN")((void)0); | |||
| 5601 | ||||
| 5602 | auto *BI = dyn_cast<BranchInst>(IDom->getTerminator()); | |||
| 5603 | Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr; | |||
| 5604 | ||||
| 5605 | if (BI && BI->isConditional() && | |||
| 5606 | BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) && | |||
| 5607 | IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) && | |||
| 5608 | IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent())) | |||
| 5609 | return createNodeForSelectOrPHI(PN, Cond, LHS, RHS); | |||
| 5610 | } | |||
| 5611 | ||||
| 5612 | return nullptr; | |||
| 5613 | } | |||
| 5614 | ||||
| 5615 | const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { | |||
| 5616 | if (const SCEV *S = createAddRecFromPHI(PN)) | |||
| 5617 | return S; | |||
| 5618 | ||||
| 5619 | if (const SCEV *S = createNodeFromSelectLikePHI(PN)) | |||
| 5620 | return S; | |||
| 5621 | ||||
| 5622 | // If the PHI has a single incoming value, follow that value, unless the | |||
| 5623 | // PHI's incoming blocks are in a different loop, in which case doing so | |||
| 5624 | // risks breaking LCSSA form. Instcombine would normally zap these, but | |||
| 5625 | // it doesn't have DominatorTree information, so it may miss cases. | |||
| 5626 | if (Value *V = SimplifyInstruction(PN, {getDataLayout(), &TLI, &DT, &AC})) | |||
| 5627 | if (LI.replacementPreservesLCSSAForm(PN, V)) | |||
| 5628 | return getSCEV(V); | |||
| 5629 | ||||
| 5630 | // If it's not a loop phi, we can't handle it yet. | |||
| 5631 | return getUnknown(PN); | |||
| 5632 | } | |||
| 5633 | ||||
| 5634 | const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I, | |||
| 5635 | Value *Cond, | |||
| 5636 | Value *TrueVal, | |||
| 5637 | Value *FalseVal) { | |||
| 5638 | // Handle "constant" branch or select. This can occur for instance when a | |||
| 5639 | // loop pass transforms an inner loop and moves on to process the outer loop. | |||
| 5640 | if (auto *CI = dyn_cast<ConstantInt>(Cond)) | |||
| 5641 | return getSCEV(CI->isOne() ? TrueVal : FalseVal); | |||
| 5642 | ||||
| 5643 | // Try to match some simple smax or umax patterns. | |||
| 5644 | auto *ICI = dyn_cast<ICmpInst>(Cond); | |||
| 5645 | if (!ICI) | |||
| 5646 | return getUnknown(I); | |||
| 5647 | ||||
| 5648 | Value *LHS = ICI->getOperand(0); | |||
| 5649 | Value *RHS = ICI->getOperand(1); | |||
| 5650 | ||||
| 5651 | switch (ICI->getPredicate()) { | |||
| 5652 | case ICmpInst::ICMP_SLT: | |||
| 5653 | case ICmpInst::ICMP_SLE: | |||
| 5654 | case ICmpInst::ICMP_ULT: | |||
| 5655 | case ICmpInst::ICMP_ULE: | |||
| 5656 | std::swap(LHS, RHS); | |||
| 5657 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 5658 | case ICmpInst::ICMP_SGT: | |||
| 5659 | case ICmpInst::ICMP_SGE: | |||
| 5660 | case ICmpInst::ICMP_UGT: | |||
| 5661 | case ICmpInst::ICMP_UGE: | |||
| 5662 | // a > b ? a+x : b+x -> max(a, b)+x | |||
| 5663 | // a > b ? b+x : a+x -> min(a, b)+x | |||
| 5664 | if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) { | |||
| 5665 | bool Signed = ICI->isSigned(); | |||
| 5666 | const SCEV *LA = getSCEV(TrueVal); | |||
| 5667 | const SCEV *RA = getSCEV(FalseVal); | |||
| 5668 | const SCEV *LS = getSCEV(LHS); | |||
| 5669 | const SCEV *RS = getSCEV(RHS); | |||
| 5670 | if (LA->getType()->isPointerTy()) { | |||
| 5671 | // FIXME: Handle cases where LS/RS are pointers not equal to LA/RA. | |||
| 5672 | // Need to make sure we can't produce weird expressions involving | |||
| 5673 | // negated pointers. | |||
| 5674 | if (LA == LS && RA == RS) | |||
| 5675 | return Signed ? getSMaxExpr(LS, RS) : getUMaxExpr(LS, RS); | |||
| 5676 | if (LA == RS && RA == LS) | |||
| 5677 | return Signed ? getSMinExpr(LS, RS) : getUMinExpr(LS, RS); | |||
| 5678 | } | |||
| 5679 | auto CoerceOperand = [&](const SCEV *Op) -> const SCEV * { | |||
| 5680 | if (Op->getType()->isPointerTy()) { | |||
| 5681 | Op = getLosslessPtrToIntExpr(Op); | |||
| 5682 | if (isa<SCEVCouldNotCompute>(Op)) | |||
| 5683 | return Op; | |||
| 5684 | } | |||
| 5685 | if (Signed) | |||
| 5686 | Op = getNoopOrSignExtend(Op, I->getType()); | |||
| 5687 | else | |||
| 5688 | Op = getNoopOrZeroExtend(Op, I->getType()); | |||
| 5689 | return Op; | |||
| 5690 | }; | |||
| 5691 | LS = CoerceOperand(LS); | |||
| 5692 | RS = CoerceOperand(RS); | |||
| 5693 | if (isa<SCEVCouldNotCompute>(LS) || isa<SCEVCouldNotCompute>(RS)) | |||
| 5694 | break; | |||
| 5695 | const SCEV *LDiff = getMinusSCEV(LA, LS); | |||
| 5696 | const SCEV *RDiff = getMinusSCEV(RA, RS); | |||
| 5697 | if (LDiff == RDiff) | |||
| 5698 | return getAddExpr(Signed ? getSMaxExpr(LS, RS) : getUMaxExpr(LS, RS), | |||
| 5699 | LDiff); | |||
| 5700 | LDiff = getMinusSCEV(LA, RS); | |||
| 5701 | RDiff = getMinusSCEV(RA, LS); | |||
| 5702 | if (LDiff == RDiff) | |||
| 5703 | return getAddExpr(Signed ? getSMinExpr(LS, RS) : getUMinExpr(LS, RS), | |||
| 5704 | LDiff); | |||
| 5705 | } | |||
| 5706 | break; | |||
| 5707 | case ICmpInst::ICMP_NE: | |||
| 5708 | // n != 0 ? n+x : 1+x -> umax(n, 1)+x | |||
| 5709 | if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) && | |||
| 5710 | isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) { | |||
| 5711 | const SCEV *One = getOne(I->getType()); | |||
| 5712 | const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType()); | |||
| 5713 | const SCEV *LA = getSCEV(TrueVal); | |||
| 5714 | const SCEV *RA = getSCEV(FalseVal); | |||
| 5715 | const SCEV *LDiff = getMinusSCEV(LA, LS); | |||
| 5716 | const SCEV *RDiff = getMinusSCEV(RA, One); | |||
| 5717 | if (LDiff == RDiff) | |||
| 5718 | return getAddExpr(getUMaxExpr(One, LS), LDiff); | |||
| 5719 | } | |||
| 5720 | break; | |||
| 5721 | case ICmpInst::ICMP_EQ: | |||
| 5722 | // n == 0 ? 1+x : n+x -> umax(n, 1)+x | |||
| 5723 | if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) && | |||
| 5724 | isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) { | |||
| 5725 | const SCEV *One = getOne(I->getType()); | |||
| 5726 | const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType()); | |||
| 5727 | const SCEV *LA = getSCEV(TrueVal); | |||
| 5728 | const SCEV *RA = getSCEV(FalseVal); | |||
| 5729 | const SCEV *LDiff = getMinusSCEV(LA, One); | |||
| 5730 | const SCEV *RDiff = getMinusSCEV(RA, LS); | |||
| 5731 | if (LDiff == RDiff) | |||
| 5732 | return getAddExpr(getUMaxExpr(One, LS), LDiff); | |||
| 5733 | } | |||
| 5734 | break; | |||
| 5735 | default: | |||
| 5736 | break; | |||
| 5737 | } | |||
| 5738 | ||||
| 5739 | return getUnknown(I); | |||
| 5740 | } | |||
| 5741 | ||||
| 5742 | /// Expand GEP instructions into add and multiply operations. This allows them | |||
| 5743 | /// to be analyzed by regular SCEV code. | |||
| 5744 | const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) { | |||
| 5745 | // Don't attempt to analyze GEPs over unsized objects. | |||
| 5746 | if (!GEP->getSourceElementType()->isSized()) | |||
| 5747 | return getUnknown(GEP); | |||
| 5748 | ||||
| 5749 | SmallVector<const SCEV *, 4> IndexExprs; | |||
| 5750 | for (Value *Index : GEP->indices()) | |||
| 5751 | IndexExprs.push_back(getSCEV(Index)); | |||
| 5752 | return getGEPExpr(GEP, IndexExprs); | |||
| 5753 | } | |||
| 5754 | ||||
| 5755 | uint32_t ScalarEvolution::GetMinTrailingZerosImpl(const SCEV *S) { | |||
| 5756 | if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) | |||
| 5757 | return C->getAPInt().countTrailingZeros(); | |||
| 5758 | ||||
| 5759 | if (const SCEVPtrToIntExpr *I = dyn_cast<SCEVPtrToIntExpr>(S)) | |||
| 5760 | return GetMinTrailingZeros(I->getOperand()); | |||
| 5761 | ||||
| 5762 | if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S)) | |||
| 5763 | return std::min(GetMinTrailingZeros(T->getOperand()), | |||
| 5764 | (uint32_t)getTypeSizeInBits(T->getType())); | |||
| 5765 | ||||
| 5766 | if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) { | |||
| 5767 | uint32_t OpRes = GetMinTrailingZeros(E->getOperand()); | |||
| 5768 | return OpRes == getTypeSizeInBits(E->getOperand()->getType()) | |||
| 5769 | ? getTypeSizeInBits(E->getType()) | |||
| 5770 | : OpRes; | |||
| 5771 | } | |||
| 5772 | ||||
| 5773 | if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) { | |||
| 5774 | uint32_t OpRes = GetMinTrailingZeros(E->getOperand()); | |||
| 5775 | return OpRes == getTypeSizeInBits(E->getOperand()->getType()) | |||
| 5776 | ? getTypeSizeInBits(E->getType()) | |||
| 5777 | : OpRes; | |||
| 5778 | } | |||
| 5779 | ||||
| 5780 | if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) { | |||
| 5781 | // The result is the min of all operands results. | |||
| 5782 | uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0)); | |||
| 5783 | for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i) | |||
| 5784 | MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i))); | |||
| 5785 | return MinOpRes; | |||
| 5786 | } | |||
| 5787 | ||||
| 5788 | if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) { | |||
| 5789 | // The result is the sum of all operands results. | |||
| 5790 | uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0)); | |||
| 5791 | uint32_t BitWidth = getTypeSizeInBits(M->getType()); | |||
| 5792 | for (unsigned i = 1, e = M->getNumOperands(); | |||
| 5793 | SumOpRes != BitWidth && i != e; ++i) | |||
| 5794 | SumOpRes = | |||
| 5795 | std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)), BitWidth); | |||
| 5796 | return SumOpRes; | |||
| 5797 | } | |||
| 5798 | ||||
| 5799 | if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) { | |||
| 5800 | // The result is the min of all operands results. | |||
| 5801 | uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0)); | |||
| 5802 | for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i) | |||
| 5803 | MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i))); | |||
| 5804 | return MinOpRes; | |||
| 5805 | } | |||
| 5806 | ||||
| 5807 | if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) { | |||
| 5808 | // The result is the min of all operands results. | |||
| 5809 | uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0)); | |||
| 5810 | for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i) | |||
| 5811 | MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i))); | |||
| 5812 | return MinOpRes; | |||
| 5813 | } | |||
| 5814 | ||||
| 5815 | if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) { | |||
| 5816 | // The result is the min of all operands results. | |||
| 5817 | uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0)); | |||
| 5818 | for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i) | |||
| 5819 | MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i))); | |||
| 5820 | return MinOpRes; | |||
| 5821 | } | |||
| 5822 | ||||
| 5823 | if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { | |||
| 5824 | // For a SCEVUnknown, ask ValueTracking. | |||
| 5825 | KnownBits Known = computeKnownBits(U->getValue(), getDataLayout(), 0, &AC, nullptr, &DT); | |||
| 5826 | return Known.countMinTrailingZeros(); | |||
| 5827 | } | |||
| 5828 | ||||
| 5829 | // SCEVUDivExpr | |||
| 5830 | return 0; | |||
| 5831 | } | |||
| 5832 | ||||
| 5833 | uint32_t ScalarEvolution::GetMinTrailingZeros(const SCEV *S) { | |||
| 5834 | auto I = MinTrailingZerosCache.find(S); | |||
| 5835 | if (I != MinTrailingZerosCache.end()) | |||
| 5836 | return I->second; | |||
| 5837 | ||||
| 5838 | uint32_t Result = GetMinTrailingZerosImpl(S); | |||
| 5839 | auto InsertPair = MinTrailingZerosCache.insert({S, Result}); | |||
| 5840 | assert(InsertPair.second && "Should insert a new key")((void)0); | |||
| 5841 | return InsertPair.first->second; | |||
| 5842 | } | |||
| 5843 | ||||
| 5844 | /// Helper method to assign a range to V from metadata present in the IR. | |||
| 5845 | static Optional<ConstantRange> GetRangeFromMetadata(Value *V) { | |||
| 5846 | if (Instruction *I = dyn_cast<Instruction>(V)) | |||
| 5847 | if (MDNode *MD = I->getMetadata(LLVMContext::MD_range)) | |||
| 5848 | return getConstantRangeFromMetadata(*MD); | |||
| 5849 | ||||
| 5850 | return None; | |||
| 5851 | } | |||
| 5852 | ||||
| 5853 | void ScalarEvolution::setNoWrapFlags(SCEVAddRecExpr *AddRec, | |||
| 5854 | SCEV::NoWrapFlags Flags) { | |||
| 5855 | if (AddRec->getNoWrapFlags(Flags) != Flags) { | |||
| 5856 | AddRec->setNoWrapFlags(Flags); | |||
| 5857 | UnsignedRanges.erase(AddRec); | |||
| 5858 | SignedRanges.erase(AddRec); | |||
| 5859 | } | |||
| 5860 | } | |||
| 5861 | ||||
| 5862 | ConstantRange ScalarEvolution:: | |||
| 5863 | getRangeForUnknownRecurrence(const SCEVUnknown *U) { | |||
| 5864 | const DataLayout &DL = getDataLayout(); | |||
| 5865 | ||||
| 5866 | unsigned BitWidth = getTypeSizeInBits(U->getType()); | |||
| 5867 | const ConstantRange FullSet(BitWidth, /*isFullSet=*/true); | |||
| 5868 | ||||
| 5869 | // Match a simple recurrence of the form: <start, ShiftOp, Step>, and then | |||
| 5870 | // use information about the trip count to improve our available range. Note | |||
| 5871 | // that the trip count independent cases are already handled by known bits. | |||
| 5872 | // WARNING: The definition of recurrence used here is subtly different than | |||
| 5873 | // the one used by AddRec (and thus most of this file). Step is allowed to | |||
| 5874 | // be arbitrarily loop varying here, where AddRec allows only loop invariant | |||
| 5875 | // and other addrecs in the same loop (for non-affine addrecs). The code | |||
| 5876 | // below intentionally handles the case where step is not loop invariant. | |||
| 5877 | auto *P = dyn_cast<PHINode>(U->getValue()); | |||
| 5878 | if (!P) | |||
| 5879 | return FullSet; | |||
| 5880 | ||||
| 5881 | // Make sure that no Phi input comes from an unreachable block. Otherwise, | |||
| 5882 | // even the values that are not available in these blocks may come from them, | |||
| 5883 | // and this leads to false-positive recurrence test. | |||
| 5884 | for (auto *Pred : predecessors(P->getParent())) | |||
| 5885 | if (!DT.isReachableFromEntry(Pred)) | |||
| 5886 | return FullSet; | |||
| 5887 | ||||
| 5888 | BinaryOperator *BO; | |||
| 5889 | Value *Start, *Step; | |||
| 5890 | if (!matchSimpleRecurrence(P, BO, Start, Step)) | |||
| 5891 | return FullSet; | |||
| 5892 | ||||
| 5893 | // If we found a recurrence in reachable code, we must be in a loop. Note | |||
| 5894 | // that BO might be in some subloop of L, and that's completely okay. | |||
| 5895 | auto *L = LI.getLoopFor(P->getParent()); | |||
| 5896 | assert(L && L->getHeader() == P->getParent())((void)0); | |||
| 5897 | if (!L->contains(BO->getParent())) | |||
| 5898 | // NOTE: This bailout should be an assert instead. However, asserting | |||
| 5899 | // the condition here exposes a case where LoopFusion is querying SCEV | |||
| 5900 | // with malformed loop information during the midst of the transform. | |||
| 5901 | // There doesn't appear to be an obvious fix, so for the moment bailout | |||
| 5902 | // until the caller issue can be fixed. PR49566 tracks the bug. | |||
| 5903 | return FullSet; | |||
| 5904 | ||||
| 5905 | // TODO: Extend to other opcodes such as mul, and div | |||
| 5906 | switch (BO->getOpcode()) { | |||
| 5907 | default: | |||
| 5908 | return FullSet; | |||
| 5909 | case Instruction::AShr: | |||
| 5910 | case Instruction::LShr: | |||
| 5911 | case Instruction::Shl: | |||
| 5912 | break; | |||
| 5913 | }; | |||
| 5914 | ||||
| 5915 | if (BO->getOperand(0) != P) | |||
| 5916 | // TODO: Handle the power function forms some day. | |||
| 5917 | return FullSet; | |||
| 5918 | ||||
| 5919 | unsigned TC = getSmallConstantMaxTripCount(L); | |||
| 5920 | if (!TC || TC >= BitWidth) | |||
| 5921 | return FullSet; | |||
| 5922 | ||||
| 5923 | auto KnownStart = computeKnownBits(Start, DL, 0, &AC, nullptr, &DT); | |||
| 5924 | auto KnownStep = computeKnownBits(Step, DL, 0, &AC, nullptr, &DT); | |||
| 5925 | assert(KnownStart.getBitWidth() == BitWidth &&((void)0) | |||
| 5926 | KnownStep.getBitWidth() == BitWidth)((void)0); | |||
| 5927 | ||||
| 5928 | // Compute total shift amount, being careful of overflow and bitwidths. | |||
| 5929 | auto MaxShiftAmt = KnownStep.getMaxValue(); | |||
| 5930 | APInt TCAP(BitWidth, TC-1); | |||
| 5931 | bool Overflow = false; | |||
| 5932 | auto TotalShift = MaxShiftAmt.umul_ov(TCAP, Overflow); | |||
| 5933 | if (Overflow) | |||
| 5934 | return FullSet; | |||
| 5935 | ||||
| 5936 | switch (BO->getOpcode()) { | |||
| 5937 | default: | |||
| 5938 | llvm_unreachable("filtered out above")__builtin_unreachable(); | |||
| 5939 | case Instruction::AShr: { | |||
| 5940 | // For each ashr, three cases: | |||
| 5941 | // shift = 0 => unchanged value | |||
| 5942 | // saturation => 0 or -1 | |||
| 5943 | // other => a value closer to zero (of the same sign) | |||
| 5944 | // Thus, the end value is closer to zero than the start. | |||
| 5945 | auto KnownEnd = KnownBits::ashr(KnownStart, | |||
| 5946 | KnownBits::makeConstant(TotalShift)); | |||
| 5947 | if (KnownStart.isNonNegative()) | |||
| 5948 | // Analogous to lshr (simply not yet canonicalized) | |||
| 5949 | return ConstantRange::getNonEmpty(KnownEnd.getMinValue(), | |||
| 5950 | KnownStart.getMaxValue() + 1); | |||
| 5951 | if (KnownStart.isNegative()) | |||
| 5952 | // End >=u Start && End <=s Start | |||
| 5953 | return ConstantRange::getNonEmpty(KnownStart.getMinValue(), | |||
| 5954 | KnownEnd.getMaxValue() + 1); | |||
| 5955 | break; | |||
| 5956 | } | |||
| 5957 | case Instruction::LShr: { | |||
| 5958 | // For each lshr, three cases: | |||
| 5959 | // shift = 0 => unchanged value | |||
| 5960 | // saturation => 0 | |||
| 5961 | // other => a smaller positive number | |||
| 5962 | // Thus, the low end of the unsigned range is the last value produced. | |||
| 5963 | auto KnownEnd = KnownBits::lshr(KnownStart, | |||
| 5964 | KnownBits::makeConstant(TotalShift)); | |||
| 5965 | return ConstantRange::getNonEmpty(KnownEnd.getMinValue(), | |||
| 5966 | KnownStart.getMaxValue() + 1); | |||
| 5967 | } | |||
| 5968 | case Instruction::Shl: { | |||
| 5969 | // Iff no bits are shifted out, value increases on every shift. | |||
| 5970 | auto KnownEnd = KnownBits::shl(KnownStart, | |||
| 5971 | KnownBits::makeConstant(TotalShift)); | |||
| 5972 | if (TotalShift.ult(KnownStart.countMinLeadingZeros())) | |||
| 5973 | return ConstantRange(KnownStart.getMinValue(), | |||
| 5974 | KnownEnd.getMaxValue() + 1); | |||
| 5975 | break; | |||
| 5976 | } | |||
| 5977 | }; | |||
| 5978 | return FullSet; | |||
| 5979 | } | |||
| 5980 | ||||
| 5981 | /// Determine the range for a particular SCEV. If SignHint is | |||
| 5982 | /// HINT_RANGE_UNSIGNED (resp. HINT_RANGE_SIGNED) then getRange prefers ranges | |||
| 5983 | /// with a "cleaner" unsigned (resp. signed) representation. | |||
| 5984 | const ConstantRange & | |||
| 5985 | ScalarEvolution::getRangeRef(const SCEV *S, | |||
| 5986 | ScalarEvolution::RangeSignHint SignHint) { | |||
| 5987 | DenseMap<const SCEV *, ConstantRange> &Cache = | |||
| 5988 | SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED ? UnsignedRanges | |||
| 5989 | : SignedRanges; | |||
| 5990 | ConstantRange::PreferredRangeType RangeType = | |||
| 5991 | SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED | |||
| 5992 | ? ConstantRange::Unsigned : ConstantRange::Signed; | |||
| 5993 | ||||
| 5994 | // See if we've computed this range already. | |||
| 5995 | DenseMap<const SCEV *, ConstantRange>::iterator I = Cache.find(S); | |||
| 5996 | if (I != Cache.end()) | |||
| 5997 | return I->second; | |||
| 5998 | ||||
| 5999 | if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) | |||
| 6000 | return setRange(C, SignHint, ConstantRange(C->getAPInt())); | |||
| 6001 | ||||
| 6002 | unsigned BitWidth = getTypeSizeInBits(S->getType()); | |||
| 6003 | ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true); | |||
| 6004 | using OBO = OverflowingBinaryOperator; | |||
| 6005 | ||||
| 6006 | // If the value has known zeros, the maximum value will have those known zeros | |||
| 6007 | // as well. | |||
| 6008 | uint32_t TZ = GetMinTrailingZeros(S); | |||
| 6009 | if (TZ != 0) { | |||
| 6010 | if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) | |||
| 6011 | ConservativeResult = | |||
| 6012 | ConstantRange(APInt::getMinValue(BitWidth), | |||
| 6013 | APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1); | |||
| 6014 | else | |||
| 6015 | ConservativeResult = ConstantRange( | |||
| 6016 | APInt::getSignedMinValue(BitWidth), | |||
| 6017 | APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1); | |||
| 6018 | } | |||
| 6019 | ||||
| 6020 | if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { | |||
| 6021 | ConstantRange X = getRangeRef(Add->getOperand(0), SignHint); | |||
| 6022 | unsigned WrapType = OBO::AnyWrap; | |||
| 6023 | if (Add->hasNoSignedWrap()) | |||
| 6024 | WrapType |= OBO::NoSignedWrap; | |||
| 6025 | if (Add->hasNoUnsignedWrap()) | |||
| 6026 | WrapType |= OBO::NoUnsignedWrap; | |||
| 6027 | for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i) | |||
| 6028 | X = X.addWithNoWrap(getRangeRef(Add->getOperand(i), SignHint), | |||
| 6029 | WrapType, RangeType); | |||
| 6030 | return setRange(Add, SignHint, | |||
| 6031 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6032 | } | |||
| 6033 | ||||
| 6034 | if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { | |||
| 6035 | ConstantRange X = getRangeRef(Mul->getOperand(0), SignHint); | |||
| 6036 | for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i) | |||
| 6037 | X = X.multiply(getRangeRef(Mul->getOperand(i), SignHint)); | |||
| 6038 | return setRange(Mul, SignHint, | |||
| 6039 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6040 | } | |||
| 6041 | ||||
| 6042 | if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) { | |||
| 6043 | ConstantRange X = getRangeRef(SMax->getOperand(0), SignHint); | |||
| 6044 | for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i) | |||
| 6045 | X = X.smax(getRangeRef(SMax->getOperand(i), SignHint)); | |||
| 6046 | return setRange(SMax, SignHint, | |||
| 6047 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6048 | } | |||
| 6049 | ||||
| 6050 | if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) { | |||
| 6051 | ConstantRange X = getRangeRef(UMax->getOperand(0), SignHint); | |||
| 6052 | for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i) | |||
| 6053 | X = X.umax(getRangeRef(UMax->getOperand(i), SignHint)); | |||
| 6054 | return setRange(UMax, SignHint, | |||
| 6055 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6056 | } | |||
| 6057 | ||||
| 6058 | if (const SCEVSMinExpr *SMin = dyn_cast<SCEVSMinExpr>(S)) { | |||
| 6059 | ConstantRange X = getRangeRef(SMin->getOperand(0), SignHint); | |||
| 6060 | for (unsigned i = 1, e = SMin->getNumOperands(); i != e; ++i) | |||
| 6061 | X = X.smin(getRangeRef(SMin->getOperand(i), SignHint)); | |||
| 6062 | return setRange(SMin, SignHint, | |||
| 6063 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6064 | } | |||
| 6065 | ||||
| 6066 | if (const SCEVUMinExpr *UMin = dyn_cast<SCEVUMinExpr>(S)) { | |||
| 6067 | ConstantRange X = getRangeRef(UMin->getOperand(0), SignHint); | |||
| 6068 | for (unsigned i = 1, e = UMin->getNumOperands(); i != e; ++i) | |||
| 6069 | X = X.umin(getRangeRef(UMin->getOperand(i), SignHint)); | |||
| 6070 | return setRange(UMin, SignHint, | |||
| 6071 | ConservativeResult.intersectWith(X, RangeType)); | |||
| 6072 | } | |||
| 6073 | ||||
| 6074 | if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) { | |||
| 6075 | ConstantRange X = getRangeRef(UDiv->getLHS(), SignHint); | |||
| 6076 | ConstantRange Y = getRangeRef(UDiv->getRHS(), SignHint); | |||
| 6077 | return setRange(UDiv, SignHint, | |||
| 6078 | ConservativeResult.intersectWith(X.udiv(Y), RangeType)); | |||
| 6079 | } | |||
| 6080 | ||||
| 6081 | if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) { | |||
| 6082 | ConstantRange X = getRangeRef(ZExt->getOperand(), SignHint); | |||
| 6083 | return setRange(ZExt, SignHint, | |||
| 6084 | ConservativeResult.intersectWith(X.zeroExtend(BitWidth), | |||
| 6085 | RangeType)); | |||
| 6086 | } | |||
| 6087 | ||||
| 6088 | if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) { | |||
| 6089 | ConstantRange X = getRangeRef(SExt->getOperand(), SignHint); | |||
| 6090 | return setRange(SExt, SignHint, | |||
| 6091 | ConservativeResult.intersectWith(X.signExtend(BitWidth), | |||
| 6092 | RangeType)); | |||
| 6093 | } | |||
| 6094 | ||||
| 6095 | if (const SCEVPtrToIntExpr *PtrToInt = dyn_cast<SCEVPtrToIntExpr>(S)) { | |||
| 6096 | ConstantRange X = getRangeRef(PtrToInt->getOperand(), SignHint); | |||
| 6097 | return setRange(PtrToInt, SignHint, X); | |||
| 6098 | } | |||
| 6099 | ||||
| 6100 | if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) { | |||
| 6101 | ConstantRange X = getRangeRef(Trunc->getOperand(), SignHint); | |||
| 6102 | return setRange(Trunc, SignHint, | |||
| 6103 | ConservativeResult.intersectWith(X.truncate(BitWidth), | |||
| 6104 | RangeType)); | |||
| 6105 | } | |||
| 6106 | ||||
| 6107 | if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) { | |||
| 6108 | // If there's no unsigned wrap, the value will never be less than its | |||
| 6109 | // initial value. | |||
| 6110 | if (AddRec->hasNoUnsignedWrap()) { | |||
| 6111 | APInt UnsignedMinValue = getUnsignedRangeMin(AddRec->getStart()); | |||
| 6112 | if (!UnsignedMinValue.isNullValue()) | |||
| 6113 | ConservativeResult = ConservativeResult.intersectWith( | |||
| 6114 | ConstantRange(UnsignedMinValue, APInt(BitWidth, 0)), RangeType); | |||
| 6115 | } | |||
| 6116 | ||||
| 6117 | // If there's no signed wrap, and all the operands except initial value have | |||
| 6118 | // the same sign or zero, the value won't ever be: | |||
| 6119 | // 1: smaller than initial value if operands are non negative, | |||
| 6120 | // 2: bigger than initial value if operands are non positive. | |||
| 6121 | // For both cases, value can not cross signed min/max boundary. | |||
| 6122 | if (AddRec->hasNoSignedWrap()) { | |||
| 6123 | bool AllNonNeg = true; | |||
| 6124 | bool AllNonPos = true; | |||
| 6125 | for (unsigned i = 1, e = AddRec->getNumOperands(); i != e; ++i) { | |||
| 6126 | if (!isKnownNonNegative(AddRec->getOperand(i))) | |||
| 6127 | AllNonNeg = false; | |||
| 6128 | if (!isKnownNonPositive(AddRec->getOperand(i))) | |||
| 6129 | AllNonPos = false; | |||
| 6130 | } | |||
| 6131 | if (AllNonNeg) | |||
| 6132 | ConservativeResult = ConservativeResult.intersectWith( | |||
| 6133 | ConstantRange::getNonEmpty(getSignedRangeMin(AddRec->getStart()), | |||
| 6134 | APInt::getSignedMinValue(BitWidth)), | |||
| 6135 | RangeType); | |||
| 6136 | else if (AllNonPos) | |||
| 6137 | ConservativeResult = ConservativeResult.intersectWith( | |||
| 6138 | ConstantRange::getNonEmpty( | |||
| 6139 | APInt::getSignedMinValue(BitWidth), | |||
| 6140 | getSignedRangeMax(AddRec->getStart()) + 1), | |||
| 6141 | RangeType); | |||
| 6142 | } | |||
| 6143 | ||||
| 6144 | // TODO: non-affine addrec | |||
| 6145 | if (AddRec->isAffine()) { | |||
| 6146 | const SCEV *MaxBECount = getConstantMaxBackedgeTakenCount(AddRec->getLoop()); | |||
| 6147 | if (!isa<SCEVCouldNotCompute>(MaxBECount) && | |||
| 6148 | getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) { | |||
| 6149 | auto RangeFromAffine = getRangeForAffineAR( | |||
| 6150 | AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount, | |||
| 6151 | BitWidth); | |||
| 6152 | ConservativeResult = | |||
| 6153 | ConservativeResult.intersectWith(RangeFromAffine, RangeType); | |||
| 6154 | ||||
| 6155 | auto RangeFromFactoring = getRangeViaFactoring( | |||
| 6156 | AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount, | |||
| 6157 | BitWidth); | |||
| 6158 | ConservativeResult = | |||
| 6159 | ConservativeResult.intersectWith(RangeFromFactoring, RangeType); | |||
| 6160 | } | |||
| 6161 | ||||
| 6162 | // Now try symbolic BE count and more powerful methods. | |||
| 6163 | if (UseExpensiveRangeSharpening) { | |||
| 6164 | const SCEV *SymbolicMaxBECount = | |||
| 6165 | getSymbolicMaxBackedgeTakenCount(AddRec->getLoop()); | |||
| 6166 | if (!isa<SCEVCouldNotCompute>(SymbolicMaxBECount) && | |||
| 6167 | getTypeSizeInBits(MaxBECount->getType()) <= BitWidth && | |||
| 6168 | AddRec->hasNoSelfWrap()) { | |||
| 6169 | auto RangeFromAffineNew = getRangeForAffineNoSelfWrappingAR( | |||
| 6170 | AddRec, SymbolicMaxBECount, BitWidth, SignHint); | |||
| 6171 | ConservativeResult = | |||
| 6172 | ConservativeResult.intersectWith(RangeFromAffineNew, RangeType); | |||
| 6173 | } | |||
| 6174 | } | |||
| 6175 | } | |||
| 6176 | ||||
| 6177 | return setRange(AddRec, SignHint, std::move(ConservativeResult)); | |||
| 6178 | } | |||
| 6179 | ||||
| 6180 | if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { | |||
| 6181 | ||||
| 6182 | // Check if the IR explicitly contains !range metadata. | |||
| 6183 | Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue()); | |||
| 6184 | if (MDRange.hasValue()) | |||
| 6185 | ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue(), | |||
| 6186 | RangeType); | |||
| 6187 | ||||
| 6188 | // Use facts about recurrences in the underlying IR. Note that add | |||
| 6189 | // recurrences are AddRecExprs and thus don't hit this path. This | |||
| 6190 | // primarily handles shift recurrences. | |||
| 6191 | auto CR = getRangeForUnknownRecurrence(U); | |||
| 6192 | ConservativeResult = ConservativeResult.intersectWith(CR); | |||
| 6193 | ||||
| 6194 | // See if ValueTracking can give us a useful range. | |||
| 6195 | const DataLayout &DL = getDataLayout(); | |||
| 6196 | KnownBits Known = computeKnownBits(U->getValue(), DL, 0, &AC, nullptr, &DT); | |||
| 6197 | if (Known.getBitWidth() != BitWidth) | |||
| 6198 | Known = Known.zextOrTrunc(BitWidth); | |||
| 6199 | ||||
| 6200 | // ValueTracking may be able to compute a tighter result for the number of | |||
| 6201 | // sign bits than for the value of those sign bits. | |||
| 6202 | unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, &AC, nullptr, &DT); | |||
| 6203 | if (U->getType()->isPointerTy()) { | |||
| 6204 | // If the pointer size is larger than the index size type, this can cause | |||
| 6205 | // NS to be larger than BitWidth. So compensate for this. | |||
| 6206 | unsigned ptrSize = DL.getPointerTypeSizeInBits(U->getType()); | |||
| 6207 | int ptrIdxDiff = ptrSize - BitWidth; | |||
| 6208 | if (ptrIdxDiff > 0 && ptrSize > BitWidth && NS > (unsigned)ptrIdxDiff) | |||
| 6209 | NS -= ptrIdxDiff; | |||
| 6210 | } | |||
| 6211 | ||||
| 6212 | if (NS > 1) { | |||
| 6213 | // If we know any of the sign bits, we know all of the sign bits. | |||
| 6214 | if (!Known.Zero.getHiBits(NS).isNullValue()) | |||
| 6215 | Known.Zero.setHighBits(NS); | |||
| 6216 | if (!Known.One.getHiBits(NS).isNullValue()) | |||
| 6217 | Known.One.setHighBits(NS); | |||
| 6218 | } | |||
| 6219 | ||||
| 6220 | if (Known.getMinValue() != Known.getMaxValue() + 1) | |||
| 6221 | ConservativeResult = ConservativeResult.intersectWith( | |||
| 6222 | ConstantRange(Known.getMinValue(), Known.getMaxValue() + 1), | |||
| 6223 | RangeType); | |||
| 6224 | if (NS > 1) | |||
| 6225 | ConservativeResult = ConservativeResult.intersectWith( | |||
| 6226 | ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1), | |||
| 6227 | APInt::getSignedMaxValue(BitWidth).ashr(NS - 1) + 1), | |||
| 6228 | RangeType); | |||
| 6229 | ||||
| 6230 | // A range of Phi is a subset of union of all ranges of its input. | |||
| 6231 | if (const PHINode *Phi = dyn_cast<PHINode>(U->getValue())) { | |||
| 6232 | // Make sure that we do not run over cycled Phis. | |||
| 6233 | if (PendingPhiRanges.insert(Phi).second) { | |||
| 6234 | ConstantRange RangeFromOps(BitWidth, /*isFullSet=*/false); | |||
| 6235 | for (auto &Op : Phi->operands()) { | |||
| 6236 | auto OpRange = getRangeRef(getSCEV(Op), SignHint); | |||
| 6237 | RangeFromOps = RangeFromOps.unionWith(OpRange); | |||
| 6238 | // No point to continue if we already have a full set. | |||
| 6239 | if (RangeFromOps.isFullSet()) | |||
| 6240 | break; | |||
| 6241 | } | |||
| 6242 | ConservativeResult = | |||
| 6243 | ConservativeResult.intersectWith(RangeFromOps, RangeType); | |||
| 6244 | bool Erased = PendingPhiRanges.erase(Phi); | |||
| 6245 | assert(Erased && "Failed to erase Phi properly?")((void)0); | |||
| 6246 | (void) Erased; | |||
| 6247 | } | |||
| 6248 | } | |||
| 6249 | ||||
| 6250 | return setRange(U, SignHint, std::move(ConservativeResult)); | |||
| 6251 | } | |||
| 6252 | ||||
| 6253 | return setRange(S, SignHint, std::move(ConservativeResult)); | |||
| 6254 | } | |||
| 6255 | ||||
| 6256 | // Given a StartRange, Step and MaxBECount for an expression compute a range of | |||
| 6257 | // values that the expression can take. Initially, the expression has a value | |||
| 6258 | // from StartRange and then is changed by Step up to MaxBECount times. Signed | |||
| 6259 | // argument defines if we treat Step as signed or unsigned. | |||
| 6260 | static ConstantRange getRangeForAffineARHelper(APInt Step, | |||
| 6261 | const ConstantRange &StartRange, | |||
| 6262 | const APInt &MaxBECount, | |||
| 6263 | unsigned BitWidth, bool Signed) { | |||
| 6264 | // If either Step or MaxBECount is 0, then the expression won't change, and we | |||
| 6265 | // just need to return the initial range. | |||
| 6266 | if (Step == 0 || MaxBECount == 0) | |||
| 6267 | return StartRange; | |||
| 6268 | ||||
| 6269 | // If we don't know anything about the initial value (i.e. StartRange is | |||
| 6270 | // FullRange), then we don't know anything about the final range either. | |||
| 6271 | // Return FullRange. | |||
| 6272 | if (StartRange.isFullSet()) | |||
| 6273 | return ConstantRange::getFull(BitWidth); | |||
| 6274 | ||||
| 6275 | // If Step is signed and negative, then we use its absolute value, but we also | |||
| 6276 | // note that we're moving in the opposite direction. | |||
| 6277 | bool Descending = Signed && Step.isNegative(); | |||
| 6278 | ||||
| 6279 | if (Signed) | |||
| 6280 | // This is correct even for INT_SMIN. Let's look at i8 to illustrate this: | |||
| 6281 | // abs(INT_SMIN) = abs(-128) = abs(0x80) = -0x80 = 0x80 = 128. | |||
| 6282 | // This equations hold true due to the well-defined wrap-around behavior of | |||
| 6283 | // APInt. | |||
| 6284 | Step = Step.abs(); | |||
| 6285 | ||||
| 6286 | // Check if Offset is more than full span of BitWidth. If it is, the | |||
| 6287 | // expression is guaranteed to overflow. | |||
| 6288 | if (APInt::getMaxValue(StartRange.getBitWidth()).udiv(Step).ult(MaxBECount)) | |||
| 6289 | return ConstantRange::getFull(BitWidth); | |||
| 6290 | ||||
| 6291 | // Offset is by how much the expression can change. Checks above guarantee no | |||
| 6292 | // overflow here. | |||
| 6293 | APInt Offset = Step * MaxBECount; | |||
| 6294 | ||||
| 6295 | // Minimum value of the final range will match the minimal value of StartRange | |||
| 6296 | // if the expression is increasing and will be decreased by Offset otherwise. | |||
| 6297 | // Maximum value of the final range will match the maximal value of StartRange | |||
| 6298 | // if the expression is decreasing and will be increased by Offset otherwise. | |||
| 6299 | APInt StartLower = StartRange.getLower(); | |||
| 6300 | APInt StartUpper = StartRange.getUpper() - 1; | |||
| 6301 | APInt MovedBoundary = Descending ? (StartLower - std::move(Offset)) | |||
| 6302 | : (StartUpper + std::move(Offset)); | |||
| 6303 | ||||
| 6304 | // It's possible that the new minimum/maximum value will fall into the initial | |||
| 6305 | // range (due to wrap around). This means that the expression can take any | |||
| 6306 | // value in this bitwidth, and we have to return full range. | |||
| 6307 | if (StartRange.contains(MovedBoundary)) | |||
| 6308 | return ConstantRange::getFull(BitWidth); | |||
| 6309 | ||||
| 6310 | APInt NewLower = | |||
| 6311 | Descending ? std::move(MovedBoundary) : std::move(StartLower); | |||
| 6312 | APInt NewUpper = | |||
| 6313 | Descending ? std::move(StartUpper) : std::move(MovedBoundary); | |||
| 6314 | NewUpper += 1; | |||
| 6315 | ||||
| 6316 | // No overflow detected, return [StartLower, StartUpper + Offset + 1) range. | |||
| 6317 | return ConstantRange::getNonEmpty(std::move(NewLower), std::move(NewUpper)); | |||
| 6318 | } | |||
| 6319 | ||||
| 6320 | ConstantRange ScalarEvolution::getRangeForAffineAR(const SCEV *Start, | |||
| 6321 | const SCEV *Step, | |||
| 6322 | const SCEV *MaxBECount, | |||
| 6323 | unsigned BitWidth) { | |||
| 6324 | assert(!isa<SCEVCouldNotCompute>(MaxBECount) &&((void)0) | |||
| 6325 | getTypeSizeInBits(MaxBECount->getType()) <= BitWidth &&((void)0) | |||
| 6326 | "Precondition!")((void)0); | |||
| 6327 | ||||
| 6328 | MaxBECount = getNoopOrZeroExtend(MaxBECount, Start->getType()); | |||
| 6329 | APInt MaxBECountValue = getUnsignedRangeMax(MaxBECount); | |||
| 6330 | ||||
| 6331 | // First, consider step signed. | |||
| 6332 | ConstantRange StartSRange = getSignedRange(Start); | |||
| 6333 | ConstantRange StepSRange = getSignedRange(Step); | |||
| 6334 | ||||
| 6335 | // If Step can be both positive and negative, we need to find ranges for the | |||
| 6336 | // maximum absolute step values in both directions and union them. | |||
| 6337 | ConstantRange SR = | |||
| 6338 | getRangeForAffineARHelper(StepSRange.getSignedMin(), StartSRange, | |||
| 6339 | MaxBECountValue, BitWidth, /* Signed = */ true); | |||
| 6340 | SR = SR.unionWith(getRangeForAffineARHelper(StepSRange.getSignedMax(), | |||
| 6341 | StartSRange, MaxBECountValue, | |||
| 6342 | BitWidth, /* Signed = */ true)); | |||
| 6343 | ||||
| 6344 | // Next, consider step unsigned. | |||
| 6345 | ConstantRange UR = getRangeForAffineARHelper( | |||
| 6346 | getUnsignedRangeMax(Step), getUnsignedRange(Start), | |||
| 6347 | MaxBECountValue, BitWidth, /* Signed = */ false); | |||
| 6348 | ||||
| 6349 | // Finally, intersect signed and unsigned ranges. | |||
| 6350 | return SR.intersectWith(UR, ConstantRange::Smallest); | |||
| 6351 | } | |||
| 6352 | ||||
| 6353 | ConstantRange ScalarEvolution::getRangeForAffineNoSelfWrappingAR( | |||
| 6354 | const SCEVAddRecExpr *AddRec, const SCEV *MaxBECount, unsigned BitWidth, | |||
| 6355 | ScalarEvolution::RangeSignHint SignHint) { | |||
| 6356 | assert(AddRec->isAffine() && "Non-affine AddRecs are not suppored!\n")((void)0); | |||
| 6357 | assert(AddRec->hasNoSelfWrap() &&((void)0) | |||
| 6358 | "This only works for non-self-wrapping AddRecs!")((void)0); | |||
| 6359 | const bool IsSigned = SignHint == HINT_RANGE_SIGNED; | |||
| 6360 | const SCEV *Step = AddRec->getStepRecurrence(*this); | |||
| 6361 | // Only deal with constant step to save compile time. | |||
| 6362 | if (!isa<SCEVConstant>(Step)) | |||
| 6363 | return ConstantRange::getFull(BitWidth); | |||
| 6364 | // Let's make sure that we can prove that we do not self-wrap during | |||
| 6365 | // MaxBECount iterations. We need this because MaxBECount is a maximum | |||
| 6366 | // iteration count estimate, and we might infer nw from some exit for which we | |||
| 6367 | // do not know max exit count (or any other side reasoning). | |||
| 6368 | // TODO: Turn into assert at some point. | |||
| 6369 | if (getTypeSizeInBits(MaxBECount->getType()) > | |||
| 6370 | getTypeSizeInBits(AddRec->getType())) | |||
| 6371 | return ConstantRange::getFull(BitWidth); | |||
| 6372 | MaxBECount = getNoopOrZeroExtend(MaxBECount, AddRec->getType()); | |||
| 6373 | const SCEV *RangeWidth = getMinusOne(AddRec->getType()); | |||
| 6374 | const SCEV *StepAbs = getUMinExpr(Step, getNegativeSCEV(Step)); | |||
| 6375 | const SCEV *MaxItersWithoutWrap = getUDivExpr(RangeWidth, StepAbs); | |||
| 6376 | if (!isKnownPredicateViaConstantRanges(ICmpInst::ICMP_ULE, MaxBECount, | |||
| 6377 | MaxItersWithoutWrap)) | |||
| 6378 | return ConstantRange::getFull(BitWidth); | |||
| 6379 | ||||
| 6380 | ICmpInst::Predicate LEPred = | |||
| 6381 | IsSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; | |||
| 6382 | ICmpInst::Predicate GEPred = | |||
| 6383 | IsSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; | |||
| 6384 | const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this); | |||
| 6385 | ||||
| 6386 | // We know that there is no self-wrap. Let's take Start and End values and | |||
| 6387 | // look at all intermediate values V1, V2, ..., Vn that IndVar takes during | |||
| 6388 | // the iteration. They either lie inside the range [Min(Start, End), | |||
| 6389 | // Max(Start, End)] or outside it: | |||
| 6390 | // | |||
| 6391 | // Case 1: RangeMin ... Start V1 ... VN End ... RangeMax; | |||
| 6392 | // Case 2: RangeMin Vk ... V1 Start ... End Vn ... Vk + 1 RangeMax; | |||
| 6393 | // | |||
| 6394 | // No self wrap flag guarantees that the intermediate values cannot be BOTH | |||
| 6395 | // outside and inside the range [Min(Start, End), Max(Start, End)]. Using that | |||
| 6396 | // knowledge, let's try to prove that we are dealing with Case 1. It is so if | |||
| 6397 | // Start <= End and step is positive, or Start >= End and step is negative. | |||
| 6398 | const SCEV *Start = AddRec->getStart(); | |||
| 6399 | ConstantRange StartRange = getRangeRef(Start, SignHint); | |||
| 6400 | ConstantRange EndRange = getRangeRef(End, SignHint); | |||
| 6401 | ConstantRange RangeBetween = StartRange.unionWith(EndRange); | |||
| 6402 | // If they already cover full iteration space, we will know nothing useful | |||
| 6403 | // even if we prove what we want to prove. | |||
| 6404 | if (RangeBetween.isFullSet()) | |||
| 6405 | return RangeBetween; | |||
| 6406 | // Only deal with ranges that do not wrap (i.e. RangeMin < RangeMax). | |||
| 6407 | bool IsWrappedSet = IsSigned ? RangeBetween.isSignWrappedSet() | |||
| 6408 | : RangeBetween.isWrappedSet(); | |||
| 6409 | if (IsWrappedSet) | |||
| 6410 | return ConstantRange::getFull(BitWidth); | |||
| 6411 | ||||
| 6412 | if (isKnownPositive(Step) && | |||
| 6413 | isKnownPredicateViaConstantRanges(LEPred, Start, End)) | |||
| 6414 | return RangeBetween; | |||
| 6415 | else if (isKnownNegative(Step) && | |||
| 6416 | isKnownPredicateViaConstantRanges(GEPred, Start, End)) | |||
| 6417 | return RangeBetween; | |||
| 6418 | return ConstantRange::getFull(BitWidth); | |||
| 6419 | } | |||
| 6420 | ||||
| 6421 | ConstantRange ScalarEvolution::getRangeViaFactoring(const SCEV *Start, | |||
| 6422 | const SCEV *Step, | |||
| 6423 | const SCEV *MaxBECount, | |||
| 6424 | unsigned BitWidth) { | |||
| 6425 | // RangeOf({C?A:B,+,C?P:Q}) == RangeOf(C?{A,+,P}:{B,+,Q}) | |||
| 6426 | // == RangeOf({A,+,P}) union RangeOf({B,+,Q}) | |||
| 6427 | ||||
| 6428 | struct SelectPattern { | |||
| 6429 | Value *Condition = nullptr; | |||
| 6430 | APInt TrueValue; | |||
| 6431 | APInt FalseValue; | |||
| 6432 | ||||
| 6433 | explicit SelectPattern(ScalarEvolution &SE, unsigned BitWidth, | |||
| 6434 | const SCEV *S) { | |||
| 6435 | Optional<unsigned> CastOp; | |||
| 6436 | APInt Offset(BitWidth, 0); | |||
| 6437 | ||||
| 6438 | assert(SE.getTypeSizeInBits(S->getType()) == BitWidth &&((void)0) | |||
| 6439 | "Should be!")((void)0); | |||
| 6440 | ||||
| 6441 | // Peel off a constant offset: | |||
| 6442 | if (auto *SA = dyn_cast<SCEVAddExpr>(S)) { | |||
| 6443 | // In the future we could consider being smarter here and handle | |||
| 6444 | // {Start+Step,+,Step} too. | |||
| 6445 | if (SA->getNumOperands() != 2 || !isa<SCEVConstant>(SA->getOperand(0))) | |||
| 6446 | return; | |||
| 6447 | ||||
| 6448 | Offset = cast<SCEVConstant>(SA->getOperand(0))->getAPInt(); | |||
| 6449 | S = SA->getOperand(1); | |||
| 6450 | } | |||
| 6451 | ||||
| 6452 | // Peel off a cast operation | |||
| 6453 | if (auto *SCast = dyn_cast<SCEVIntegralCastExpr>(S)) { | |||
| 6454 | CastOp = SCast->getSCEVType(); | |||
| 6455 | S = SCast->getOperand(); | |||
| 6456 | } | |||
| 6457 | ||||
| 6458 | using namespace llvm::PatternMatch; | |||
| 6459 | ||||
| 6460 | auto *SU = dyn_cast<SCEVUnknown>(S); | |||
| 6461 | const APInt *TrueVal, *FalseVal; | |||
| 6462 | if (!SU || | |||
| 6463 | !match(SU->getValue(), m_Select(m_Value(Condition), m_APInt(TrueVal), | |||
| 6464 | m_APInt(FalseVal)))) { | |||
| 6465 | Condition = nullptr; | |||
| 6466 | return; | |||
| 6467 | } | |||
| 6468 | ||||
| 6469 | TrueValue = *TrueVal; | |||
| 6470 | FalseValue = *FalseVal; | |||
| 6471 | ||||
| 6472 | // Re-apply the cast we peeled off earlier | |||
| 6473 | if (CastOp.hasValue()) | |||
| 6474 | switch (*CastOp) { | |||
| 6475 | default: | |||
| 6476 | llvm_unreachable("Unknown SCEV cast type!")__builtin_unreachable(); | |||
| 6477 | ||||
| 6478 | case scTruncate: | |||
| 6479 | TrueValue = TrueValue.trunc(BitWidth); | |||
| 6480 | FalseValue = FalseValue.trunc(BitWidth); | |||
| 6481 | break; | |||
| 6482 | case scZeroExtend: | |||
| 6483 | TrueValue = TrueValue.zext(BitWidth); | |||
| 6484 | FalseValue = FalseValue.zext(BitWidth); | |||
| 6485 | break; | |||
| 6486 | case scSignExtend: | |||
| 6487 | TrueValue = TrueValue.sext(BitWidth); | |||
| 6488 | FalseValue = FalseValue.sext(BitWidth); | |||
| 6489 | break; | |||
| 6490 | } | |||
| 6491 | ||||
| 6492 | // Re-apply the constant offset we peeled off earlier | |||
| 6493 | TrueValue += Offset; | |||
| 6494 | FalseValue += Offset; | |||
| 6495 | } | |||
| 6496 | ||||
| 6497 | bool isRecognized() { return Condition != nullptr; } | |||
| 6498 | }; | |||
| 6499 | ||||
| 6500 | SelectPattern StartPattern(*this, BitWidth, Start); | |||
| 6501 | if (!StartPattern.isRecognized()) | |||
| 6502 | return ConstantRange::getFull(BitWidth); | |||
| 6503 | ||||
| 6504 | SelectPattern StepPattern(*this, BitWidth, Step); | |||
| 6505 | if (!StepPattern.isRecognized()) | |||
| 6506 | return ConstantRange::getFull(BitWidth); | |||
| 6507 | ||||
| 6508 | if (StartPattern.Condition != StepPattern.Condition) { | |||
| 6509 | // We don't handle this case today; but we could, by considering four | |||
| 6510 | // possibilities below instead of two. I'm not sure if there are cases where | |||
| 6511 | // that will help over what getRange already does, though. | |||
| 6512 | return ConstantRange::getFull(BitWidth); | |||
| 6513 | } | |||
| 6514 | ||||
| 6515 | // NB! Calling ScalarEvolution::getConstant is fine, but we should not try to | |||
| 6516 | // construct arbitrary general SCEV expressions here. This function is called | |||
| 6517 | // from deep in the call stack, and calling getSCEV (on a sext instruction, | |||
| 6518 | // say) can end up caching a suboptimal value. | |||
| 6519 | ||||
| 6520 | // FIXME: without the explicit `this` receiver below, MSVC errors out with | |||
| 6521 | // C2352 and C2512 (otherwise it isn't needed). | |||
| 6522 | ||||
| 6523 | const SCEV *TrueStart = this->getConstant(StartPattern.TrueValue); | |||
| 6524 | const SCEV *TrueStep = this->getConstant(StepPattern.TrueValue); | |||
| 6525 | const SCEV *FalseStart = this->getConstant(StartPattern.FalseValue); | |||
| 6526 | const SCEV *FalseStep = this->getConstant(StepPattern.FalseValue); | |||
| 6527 | ||||
| 6528 | ConstantRange TrueRange = | |||
| 6529 | this->getRangeForAffineAR(TrueStart, TrueStep, MaxBECount, BitWidth); | |||
| 6530 | ConstantRange FalseRange = | |||
| 6531 | this->getRangeForAffineAR(FalseStart, FalseStep, MaxBECount, BitWidth); | |||
| 6532 | ||||
| 6533 | return TrueRange.unionWith(FalseRange); | |||
| 6534 | } | |||
| 6535 | ||||
| 6536 | SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) { | |||
| 6537 | if (isa<ConstantExpr>(V)) return SCEV::FlagAnyWrap; | |||
| 6538 | const BinaryOperator *BinOp = cast<BinaryOperator>(V); | |||
| 6539 | ||||
| 6540 | // Return early if there are no flags to propagate to the SCEV. | |||
| 6541 | SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; | |||
| 6542 | if (BinOp->hasNoUnsignedWrap()) | |||
| 6543 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW); | |||
| 6544 | if (BinOp->hasNoSignedWrap()) | |||
| 6545 | Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW); | |||
| 6546 | if (Flags == SCEV::FlagAnyWrap) | |||
| 6547 | return SCEV::FlagAnyWrap; | |||
| 6548 | ||||
| 6549 | return isSCEVExprNeverPoison(BinOp) ? Flags : SCEV::FlagAnyWrap; | |||
| 6550 | } | |||
| 6551 | ||||
| 6552 | bool ScalarEvolution::isSCEVExprNeverPoison(const Instruction *I) { | |||
| 6553 | // Here we check that I is in the header of the innermost loop containing I, | |||
| 6554 | // since we only deal with instructions in the loop header. The actual loop we | |||
| 6555 | // need to check later will come from an add recurrence, but getting that | |||
| 6556 | // requires computing the SCEV of the operands, which can be expensive. This | |||
| 6557 | // check we can do cheaply to rule out some cases early. | |||
| 6558 | Loop *InnermostContainingLoop = LI.getLoopFor(I->getParent()); | |||
| 6559 | if (InnermostContainingLoop == nullptr || | |||
| 6560 | InnermostContainingLoop->getHeader() != I->getParent()) | |||
| 6561 | return false; | |||
| 6562 | ||||
| 6563 | // Only proceed if we can prove that I does not yield poison. | |||
| 6564 | if (!programUndefinedIfPoison(I)) | |||
| 6565 | return false; | |||
| 6566 | ||||
| 6567 | // At this point we know that if I is executed, then it does not wrap | |||
| 6568 | // according to at least one of NSW or NUW. If I is not executed, then we do | |||
| 6569 | // not know if the calculation that I represents would wrap. Multiple | |||
| 6570 | // instructions can map to the same SCEV. If we apply NSW or NUW from I to | |||
| 6571 | // the SCEV, we must guarantee no wrapping for that SCEV also when it is | |||
| 6572 | // derived from other instructions that map to the same SCEV. We cannot make | |||
| 6573 | // that guarantee for cases where I is not executed. So we need to find the | |||
| 6574 | // loop that I is considered in relation to and prove that I is executed for | |||
| 6575 | // every iteration of that loop. That implies that the value that I | |||
| 6576 | // calculates does not wrap anywhere in the loop, so then we can apply the | |||
| 6577 | // flags to the SCEV. | |||
| 6578 | // | |||
| 6579 | // We check isLoopInvariant to disambiguate in case we are adding recurrences | |||
| 6580 | // from different loops, so that we know which loop to prove that I is | |||
| 6581 | // executed in. | |||
| 6582 | for (unsigned OpIndex = 0; OpIndex < I->getNumOperands(); ++OpIndex) { | |||
| 6583 | // I could be an extractvalue from a call to an overflow intrinsic. | |||
| 6584 | // TODO: We can do better here in some cases. | |||
| 6585 | if (!isSCEVable(I->getOperand(OpIndex)->getType())) | |||
| 6586 | return false; | |||
| 6587 | const SCEV *Op = getSCEV(I->getOperand(OpIndex)); | |||
| 6588 | if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) { | |||
| 6589 | bool AllOtherOpsLoopInvariant = true; | |||
| 6590 | for (unsigned OtherOpIndex = 0; OtherOpIndex < I->getNumOperands(); | |||
| 6591 | ++OtherOpIndex) { | |||
| 6592 | if (OtherOpIndex != OpIndex) { | |||
| 6593 | const SCEV *OtherOp = getSCEV(I->getOperand(OtherOpIndex)); | |||
| 6594 | if (!isLoopInvariant(OtherOp, AddRec->getLoop())) { | |||
| 6595 | AllOtherOpsLoopInvariant = false; | |||
| 6596 | break; | |||
| 6597 | } | |||
| 6598 | } | |||
| 6599 | } | |||
| 6600 | if (AllOtherOpsLoopInvariant && | |||
| 6601 | isGuaranteedToExecuteForEveryIteration(I, AddRec->getLoop())) | |||
| 6602 | return true; | |||
| 6603 | } | |||
| 6604 | } | |||
| 6605 | return false; | |||
| 6606 | } | |||
| 6607 | ||||
| 6608 | bool ScalarEvolution::isAddRecNeverPoison(const Instruction *I, const Loop *L) { | |||
| 6609 | // If we know that \c I can never be poison period, then that's enough. | |||
| 6610 | if (isSCEVExprNeverPoison(I)) | |||
| 6611 | return true; | |||
| 6612 | ||||
| 6613 | // For an add recurrence specifically, we assume that infinite loops without | |||
| 6614 | // side effects are undefined behavior, and then reason as follows: | |||
| 6615 | // | |||
| 6616 | // If the add recurrence is poison in any iteration, it is poison on all | |||
| 6617 | // future iterations (since incrementing poison yields poison). If the result | |||
| 6618 | // of the add recurrence is fed into the loop latch condition and the loop | |||
| 6619 | // does not contain any throws or exiting blocks other than the latch, we now | |||
| 6620 | // have the ability to "choose" whether the backedge is taken or not (by | |||
| 6621 | // choosing a sufficiently evil value for the poison feeding into the branch) | |||
| 6622 | // for every iteration including and after the one in which \p I first became | |||
| 6623 | // poison. There are two possibilities (let's call the iteration in which \p | |||
| 6624 | // I first became poison as K): | |||
| 6625 | // | |||
| 6626 | // 1. In the set of iterations including and after K, the loop body executes | |||
| 6627 | // no side effects. In this case executing the backege an infinte number | |||
| 6628 | // of times will yield undefined behavior. | |||
| 6629 | // | |||
| 6630 | // 2. In the set of iterations including and after K, the loop body executes | |||
| 6631 | // at least one side effect. In this case, that specific instance of side | |||
| 6632 | // effect is control dependent on poison, which also yields undefined | |||
| 6633 | // behavior. | |||
| 6634 | ||||
| 6635 | auto *ExitingBB = L->getExitingBlock(); | |||
| 6636 | auto *LatchBB = L->getLoopLatch(); | |||
| 6637 | if (!ExitingBB || !LatchBB || ExitingBB != LatchBB) | |||
| 6638 | return false; | |||
| 6639 | ||||
| 6640 | SmallPtrSet<const Instruction *, 16> Pushed; | |||
| 6641 | SmallVector<const Instruction *, 8> PoisonStack; | |||
| 6642 | ||||
| 6643 | // We start by assuming \c I, the post-inc add recurrence, is poison. Only | |||
| 6644 | // things that are known to be poison under that assumption go on the | |||
| 6645 | // PoisonStack. | |||
| 6646 | Pushed.insert(I); | |||
| 6647 | PoisonStack.push_back(I); | |||
| 6648 | ||||
| 6649 | bool LatchControlDependentOnPoison = false; | |||
| 6650 | while (!PoisonStack.empty() && !LatchControlDependentOnPoison) { | |||
| 6651 | const Instruction *Poison = PoisonStack.pop_back_val(); | |||
| 6652 | ||||
| 6653 | for (auto *PoisonUser : Poison->users()) { | |||
| 6654 | if (propagatesPoison(cast<Operator>(PoisonUser))) { | |||
| 6655 | if (Pushed.insert(cast<Instruction>(PoisonUser)).second) | |||
| 6656 | PoisonStack.push_back(cast<Instruction>(PoisonUser)); | |||
| 6657 | } else if (auto *BI = dyn_cast<BranchInst>(PoisonUser)) { | |||
| 6658 | assert(BI->isConditional() && "Only possibility!")((void)0); | |||
| 6659 | if (BI->getParent() == LatchBB) { | |||
| 6660 | LatchControlDependentOnPoison = true; | |||
| 6661 | break; | |||
| 6662 | } | |||
| 6663 | } | |||
| 6664 | } | |||
| 6665 | } | |||
| 6666 | ||||
| 6667 | return LatchControlDependentOnPoison && loopHasNoAbnormalExits(L); | |||
| 6668 | } | |||
| 6669 | ||||
| 6670 | ScalarEvolution::LoopProperties | |||
| 6671 | ScalarEvolution::getLoopProperties(const Loop *L) { | |||
| 6672 | using LoopProperties = ScalarEvolution::LoopProperties; | |||
| 6673 | ||||
| 6674 | auto Itr = LoopPropertiesCache.find(L); | |||
| 6675 | if (Itr == LoopPropertiesCache.end()) { | |||
| 6676 | auto HasSideEffects = [](Instruction *I) { | |||
| 6677 | if (auto *SI = dyn_cast<StoreInst>(I)) | |||
| 6678 | return !SI->isSimple(); | |||
| 6679 | ||||
| 6680 | return I->mayThrow() || I->mayWriteToMemory(); | |||
| 6681 | }; | |||
| 6682 | ||||
| 6683 | LoopProperties LP = {/* HasNoAbnormalExits */ true, | |||
| 6684 | /*HasNoSideEffects*/ true}; | |||
| 6685 | ||||
| 6686 | for (auto *BB : L->getBlocks()) | |||
| 6687 | for (auto &I : *BB) { | |||
| 6688 | if (!isGuaranteedToTransferExecutionToSuccessor(&I)) | |||
| 6689 | LP.HasNoAbnormalExits = false; | |||
| 6690 | if (HasSideEffects(&I)) | |||
| 6691 | LP.HasNoSideEffects = false; | |||
| 6692 | if (!LP.HasNoAbnormalExits && !LP.HasNoSideEffects) | |||
| 6693 | break; // We're already as pessimistic as we can get. | |||
| 6694 | } | |||
| 6695 | ||||
| 6696 | auto InsertPair = LoopPropertiesCache.insert({L, LP}); | |||
| 6697 | assert(InsertPair.second && "We just checked!")((void)0); | |||
| 6698 | Itr = InsertPair.first; | |||
| 6699 | } | |||
| 6700 | ||||
| 6701 | return Itr->second; | |||
| 6702 | } | |||
| 6703 | ||||
| 6704 | bool ScalarEvolution::loopIsFiniteByAssumption(const Loop *L) { | |||
| 6705 | // A mustprogress loop without side effects must be finite. | |||
| 6706 | // TODO: The check used here is very conservative. It's only *specific* | |||
| 6707 | // side effects which are well defined in infinite loops. | |||
| 6708 | return isMustProgress(L) && loopHasNoSideEffects(L); | |||
| 6709 | } | |||
| 6710 | ||||
| 6711 | const SCEV *ScalarEvolution::createSCEV(Value *V) { | |||
| 6712 | if (!isSCEVable(V->getType())) | |||
| 6713 | return getUnknown(V); | |||
| 6714 | ||||
| 6715 | if (Instruction *I = dyn_cast<Instruction>(V)) { | |||
| 6716 | // Don't attempt to analyze instructions in blocks that aren't | |||
| 6717 | // reachable. Such instructions don't matter, and they aren't required | |||
| 6718 | // to obey basic rules for definitions dominating uses which this | |||
| 6719 | // analysis depends on. | |||
| 6720 | if (!DT.isReachableFromEntry(I->getParent())) | |||
| 6721 | return getUnknown(UndefValue::get(V->getType())); | |||
| 6722 | } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) | |||
| 6723 | return getConstant(CI); | |||
| 6724 | else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) | |||
| 6725 | return GA->isInterposable() ? getUnknown(V) : getSCEV(GA->getAliasee()); | |||
| 6726 | else if (!isa<ConstantExpr>(V)) | |||
| 6727 | return getUnknown(V); | |||
| 6728 | ||||
| 6729 | Operator *U = cast<Operator>(V); | |||
| 6730 | if (auto BO = MatchBinaryOp(U, DT)) { | |||
| 6731 | switch (BO->Opcode) { | |||
| 6732 | case Instruction::Add: { | |||
| 6733 | // The simple thing to do would be to just call getSCEV on both operands | |||
| 6734 | // and call getAddExpr with the result. However if we're looking at a | |||
| 6735 | // bunch of things all added together, this can be quite inefficient, | |||
| 6736 | // because it leads to N-1 getAddExpr calls for N ultimate operands. | |||
| 6737 | // Instead, gather up all the operands and make a single getAddExpr call. | |||
| 6738 | // LLVM IR canonical form means we need only traverse the left operands. | |||
| 6739 | SmallVector<const SCEV *, 4> AddOps; | |||
| 6740 | do { | |||
| 6741 | if (BO->Op) { | |||
| 6742 | if (auto *OpSCEV = getExistingSCEV(BO->Op)) { | |||
| 6743 | AddOps.push_back(OpSCEV); | |||
| 6744 | break; | |||
| 6745 | } | |||
| 6746 | ||||
| 6747 | // If a NUW or NSW flag can be applied to the SCEV for this | |||
| 6748 | // addition, then compute the SCEV for this addition by itself | |||
| 6749 | // with a separate call to getAddExpr. We need to do that | |||
| 6750 | // instead of pushing the operands of the addition onto AddOps, | |||
| 6751 | // since the flags are only known to apply to this particular | |||
| 6752 | // addition - they may not apply to other additions that can be | |||
| 6753 | // formed with operands from AddOps. | |||
| 6754 | const SCEV *RHS = getSCEV(BO->RHS); | |||
| 6755 | SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op); | |||
| 6756 | if (Flags != SCEV::FlagAnyWrap) { | |||
| 6757 | const SCEV *LHS = getSCEV(BO->LHS); | |||
| 6758 | if (BO->Opcode == Instruction::Sub) | |||
| 6759 | AddOps.push_back(getMinusSCEV(LHS, RHS, Flags)); | |||
| 6760 | else | |||
| 6761 | AddOps.push_back(getAddExpr(LHS, RHS, Flags)); | |||
| 6762 | break; | |||
| 6763 | } | |||
| 6764 | } | |||
| 6765 | ||||
| 6766 | if (BO->Opcode == Instruction::Sub) | |||
| 6767 | AddOps.push_back(getNegativeSCEV(getSCEV(BO->RHS))); | |||
| 6768 | else | |||
| 6769 | AddOps.push_back(getSCEV(BO->RHS)); | |||
| 6770 | ||||
| 6771 | auto NewBO = MatchBinaryOp(BO->LHS, DT); | |||
| 6772 | if (!NewBO || (NewBO->Opcode != Instruction::Add && | |||
| 6773 | NewBO->Opcode != Instruction::Sub)) { | |||
| 6774 | AddOps.push_back(getSCEV(BO->LHS)); | |||
| 6775 | break; | |||
| 6776 | } | |||
| 6777 | BO = NewBO; | |||
| 6778 | } while (true); | |||
| 6779 | ||||
| 6780 | return getAddExpr(AddOps); | |||
| 6781 | } | |||
| 6782 | ||||
| 6783 | case Instruction::Mul: { | |||
| 6784 | SmallVector<const SCEV *, 4> MulOps; | |||
| 6785 | do { | |||
| 6786 | if (BO->Op) { | |||
| 6787 | if (auto *OpSCEV = getExistingSCEV(BO->Op)) { | |||
| 6788 | MulOps.push_back(OpSCEV); | |||
| 6789 | break; | |||
| 6790 | } | |||
| 6791 | ||||
| 6792 | SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op); | |||
| 6793 | if (Flags != SCEV::FlagAnyWrap) { | |||
| 6794 | MulOps.push_back( | |||
| 6795 | getMulExpr(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags)); | |||
| 6796 | break; | |||
| 6797 | } | |||
| 6798 | } | |||
| 6799 | ||||
| 6800 | MulOps.push_back(getSCEV(BO->RHS)); | |||
| 6801 | auto NewBO = MatchBinaryOp(BO->LHS, DT); | |||
| 6802 | if (!NewBO || NewBO->Opcode != Instruction::Mul) { | |||
| 6803 | MulOps.push_back(getSCEV(BO->LHS)); | |||
| 6804 | break; | |||
| 6805 | } | |||
| 6806 | BO = NewBO; | |||
| 6807 | } while (true); | |||
| 6808 | ||||
| 6809 | return getMulExpr(MulOps); | |||
| 6810 | } | |||
| 6811 | case Instruction::UDiv: | |||
| 6812 | return getUDivExpr(getSCEV(BO->LHS), getSCEV(BO->RHS)); | |||
| 6813 | case Instruction::URem: | |||
| 6814 | return getURemExpr(getSCEV(BO->LHS), getSCEV(BO->RHS)); | |||
| 6815 | case Instruction::Sub: { | |||
| 6816 | SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; | |||
| 6817 | if (BO->Op) | |||
| 6818 | Flags = getNoWrapFlagsFromUB(BO->Op); | |||
| 6819 | return getMinusSCEV(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags); | |||
| 6820 | } | |||
| 6821 | case Instruction::And: | |||
| 6822 | // For an expression like x&255 that merely masks off the high bits, | |||
| 6823 | // use zext(trunc(x)) as the SCEV expression. | |||
| 6824 | if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) { | |||
| 6825 | if (CI->isZero()) | |||
| 6826 | return getSCEV(BO->RHS); | |||
| 6827 | if (CI->isMinusOne()) | |||
| 6828 | return getSCEV(BO->LHS); | |||
| 6829 | const APInt &A = CI->getValue(); | |||
| 6830 | ||||
| 6831 | // Instcombine's ShrinkDemandedConstant may strip bits out of | |||
| 6832 | // constants, obscuring what would otherwise be a low-bits mask. | |||
| 6833 | // Use computeKnownBits to compute what ShrinkDemandedConstant | |||
| 6834 | // knew about to reconstruct a low-bits mask value. | |||
| 6835 | unsigned LZ = A.countLeadingZeros(); | |||
| 6836 | unsigned TZ = A.countTrailingZeros(); | |||
| 6837 | unsigned BitWidth = A.getBitWidth(); | |||
| 6838 | KnownBits Known(BitWidth); | |||
| 6839 | computeKnownBits(BO->LHS, Known, getDataLayout(), | |||
| 6840 | 0, &AC, nullptr, &DT); | |||
| 6841 | ||||
| 6842 | APInt EffectiveMask = | |||
| 6843 | APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ); | |||
| 6844 | if ((LZ != 0 || TZ != 0) && !((~A & ~Known.Zero) & EffectiveMask)) { | |||
| 6845 | const SCEV *MulCount = getConstant(APInt::getOneBitSet(BitWidth, TZ)); | |||
| 6846 | const SCEV *LHS = getSCEV(BO->LHS); | |||
| 6847 | const SCEV *ShiftedLHS = nullptr; | |||
| 6848 | if (auto *LHSMul = dyn_cast<SCEVMulExpr>(LHS)) { | |||
| 6849 | if (auto *OpC = dyn_cast<SCEVConstant>(LHSMul->getOperand(0))) { | |||
| 6850 | // For an expression like (x * 8) & 8, simplify the multiply. | |||
| 6851 | unsigned MulZeros = OpC->getAPInt().countTrailingZeros(); | |||
| 6852 | unsigned GCD = std::min(MulZeros, TZ); | |||
| 6853 | APInt DivAmt = APInt::getOneBitSet(BitWidth, TZ - GCD); | |||
| 6854 | SmallVector<const SCEV*, 4> MulOps; | |||
| 6855 | MulOps.push_back(getConstant(OpC->getAPInt().lshr(GCD))); | |||
| 6856 | MulOps.append(LHSMul->op_begin() + 1, LHSMul->op_end()); | |||
| 6857 | auto *NewMul = getMulExpr(MulOps, LHSMul->getNoWrapFlags()); | |||
| 6858 | ShiftedLHS = getUDivExpr(NewMul, getConstant(DivAmt)); | |||
| 6859 | } | |||
| 6860 | } | |||
| 6861 | if (!ShiftedLHS) | |||
| 6862 | ShiftedLHS = getUDivExpr(LHS, MulCount); | |||
| 6863 | return getMulExpr( | |||
| 6864 | getZeroExtendExpr( | |||
| 6865 | getTruncateExpr(ShiftedLHS, | |||
| 6866 | IntegerType::get(getContext(), BitWidth - LZ - TZ)), | |||
| 6867 | BO->LHS->getType()), | |||
| 6868 | MulCount); | |||
| 6869 | } | |||
| 6870 | } | |||
| 6871 | break; | |||
| 6872 | ||||
| 6873 | case Instruction::Or: | |||
| 6874 | // If the RHS of the Or is a constant, we may have something like: | |||
| 6875 | // X*4+1 which got turned into X*4|1. Handle this as an Add so loop | |||
| 6876 | // optimizations will transparently handle this case. | |||
| 6877 | // | |||
| 6878 | // In order for this transformation to be safe, the LHS must be of the | |||
| 6879 | // form X*(2^n) and the Or constant must be less than 2^n. | |||
| 6880 | if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) { | |||
| 6881 | const SCEV *LHS = getSCEV(BO->LHS); | |||
| 6882 | const APInt &CIVal = CI->getValue(); | |||
| 6883 | if (GetMinTrailingZeros(LHS) >= | |||
| 6884 | (CIVal.getBitWidth() - CIVal.countLeadingZeros())) { | |||
| 6885 | // Build a plain add SCEV. | |||
| 6886 | return getAddExpr(LHS, getSCEV(CI), | |||
| 6887 | (SCEV::NoWrapFlags)(SCEV::FlagNUW | SCEV::FlagNSW)); | |||
| 6888 | } | |||
| 6889 | } | |||
| 6890 | break; | |||
| 6891 | ||||
| 6892 | case Instruction::Xor: | |||
| 6893 | if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) { | |||
| 6894 | // If the RHS of xor is -1, then this is a not operation. | |||
| 6895 | if (CI->isMinusOne()) | |||
| 6896 | return getNotSCEV(getSCEV(BO->LHS)); | |||
| 6897 | ||||
| 6898 | // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask. | |||
| 6899 | // This is a variant of the check for xor with -1, and it handles | |||
| 6900 | // the case where instcombine has trimmed non-demanded bits out | |||
| 6901 | // of an xor with -1. | |||
| 6902 | if (auto *LBO = dyn_cast<BinaryOperator>(BO->LHS)) | |||
| 6903 | if (ConstantInt *LCI = dyn_cast<ConstantInt>(LBO->getOperand(1))) | |||
| 6904 | if (LBO->getOpcode() == Instruction::And && | |||
| 6905 | LCI->getValue() == CI->getValue()) | |||
| 6906 | if (const SCEVZeroExtendExpr *Z = | |||
| 6907 | dyn_cast<SCEVZeroExtendExpr>(getSCEV(BO->LHS))) { | |||
| 6908 | Type *UTy = BO->LHS->getType(); | |||
| 6909 | const SCEV *Z0 = Z->getOperand(); | |||
| 6910 | Type *Z0Ty = Z0->getType(); | |||
| 6911 | unsigned Z0TySize = getTypeSizeInBits(Z0Ty); | |||
| 6912 | ||||
| 6913 | // If C is a low-bits mask, the zero extend is serving to | |||
| 6914 | // mask off the high bits. Complement the operand and | |||
| 6915 | // re-apply the zext. | |||
| 6916 | if (CI->getValue().isMask(Z0TySize)) | |||
| 6917 | return getZeroExtendExpr(getNotSCEV(Z0), UTy); | |||
| 6918 | ||||
| 6919 | // If C is a single bit, it may be in the sign-bit position | |||
| 6920 | // before the zero-extend. In this case, represent the xor | |||
| 6921 | // using an add, which is equivalent, and re-apply the zext. | |||
| 6922 | APInt Trunc = CI->getValue().trunc(Z0TySize); | |||
| 6923 | if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() && | |||
| 6924 | Trunc.isSignMask()) | |||
| 6925 | return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)), | |||
| 6926 | UTy); | |||
| 6927 | } | |||
| 6928 | } | |||
| 6929 | break; | |||
| 6930 | ||||
| 6931 | case Instruction::Shl: | |||
| 6932 | // Turn shift left of a constant amount into a multiply. | |||
| 6933 | if (ConstantInt *SA = dyn_cast<ConstantInt>(BO->RHS)) { | |||
| 6934 | uint32_t BitWidth = cast<IntegerType>(SA->getType())->getBitWidth(); | |||
| 6935 | ||||
| 6936 | // If the shift count is not less than the bitwidth, the result of | |||
| 6937 | // the shift is undefined. Don't try to analyze it, because the | |||
| 6938 | // resolution chosen here may differ from the resolution chosen in | |||
| 6939 | // other parts of the compiler. | |||
| 6940 | if (SA->getValue().uge(BitWidth)) | |||
| 6941 | break; | |||
| 6942 | ||||
| 6943 | // We can safely preserve the nuw flag in all cases. It's also safe to | |||
| 6944 | // turn a nuw nsw shl into a nuw nsw mul. However, nsw in isolation | |||
| 6945 | // requires special handling. It can be preserved as long as we're not | |||
| 6946 | // left shifting by bitwidth - 1. | |||
| 6947 | auto Flags = SCEV::FlagAnyWrap; | |||
| 6948 | if (BO->Op) { | |||
| 6949 | auto MulFlags = getNoWrapFlagsFromUB(BO->Op); | |||
| 6950 | if ((MulFlags & SCEV::FlagNSW) && | |||
| 6951 | ((MulFlags & SCEV::FlagNUW) || SA->getValue().ult(BitWidth - 1))) | |||
| 6952 | Flags = (SCEV::NoWrapFlags)(Flags | SCEV::FlagNSW); | |||
| 6953 | if (MulFlags & SCEV::FlagNUW) | |||
| 6954 | Flags = (SCEV::NoWrapFlags)(Flags | SCEV::FlagNUW); | |||
| 6955 | } | |||
| 6956 | ||||
| 6957 | Constant *X = ConstantInt::get( | |||
| 6958 | getContext(), APInt::getOneBitSet(BitWidth, SA->getZExtValue())); | |||
| 6959 | return getMulExpr(getSCEV(BO->LHS), getSCEV(X), Flags); | |||
| 6960 | } | |||
| 6961 | break; | |||
| 6962 | ||||
| 6963 | case Instruction::AShr: { | |||
| 6964 | // AShr X, C, where C is a constant. | |||
| 6965 | ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS); | |||
| 6966 | if (!CI) | |||
| 6967 | break; | |||
| 6968 | ||||
| 6969 | Type *OuterTy = BO->LHS->getType(); | |||
| 6970 | uint64_t BitWidth = getTypeSizeInBits(OuterTy); | |||
| 6971 | // If the shift count is not less than the bitwidth, the result of | |||
| 6972 | // the shift is undefined. Don't try to analyze it, because the | |||
| 6973 | // resolution chosen here may differ from the resolution chosen in | |||
| 6974 | // other parts of the compiler. | |||
| 6975 | if (CI->getValue().uge(BitWidth)) | |||
| 6976 | break; | |||
| 6977 | ||||
| 6978 | if (CI->isZero()) | |||
| 6979 | return getSCEV(BO->LHS); // shift by zero --> noop | |||
| 6980 | ||||
| 6981 | uint64_t AShrAmt = CI->getZExtValue(); | |||
| 6982 | Type *TruncTy = IntegerType::get(getContext(), BitWidth - AShrAmt); | |||
| 6983 | ||||
| 6984 | Operator *L = dyn_cast<Operator>(BO->LHS); | |||
| 6985 | if (L && L->getOpcode() == Instruction::Shl) { | |||
| 6986 | // X = Shl A, n | |||
| 6987 | // Y = AShr X, m | |||
| 6988 | // Both n and m are constant. | |||
| 6989 | ||||
| 6990 | const SCEV *ShlOp0SCEV = getSCEV(L->getOperand(0)); | |||
| 6991 | if (L->getOperand(1) == BO->RHS) | |||
| 6992 | // For a two-shift sext-inreg, i.e. n = m, | |||
| 6993 | // use sext(trunc(x)) as the SCEV expression. | |||
| 6994 | return getSignExtendExpr( | |||
| 6995 | getTruncateExpr(ShlOp0SCEV, TruncTy), OuterTy); | |||
| 6996 | ||||
| 6997 | ConstantInt *ShlAmtCI = dyn_cast<ConstantInt>(L->getOperand(1)); | |||
| 6998 | if (ShlAmtCI && ShlAmtCI->getValue().ult(BitWidth)) { | |||
| 6999 | uint64_t ShlAmt = ShlAmtCI->getZExtValue(); | |||
| 7000 | if (ShlAmt > AShrAmt) { | |||
| 7001 | // When n > m, use sext(mul(trunc(x), 2^(n-m)))) as the SCEV | |||
| 7002 | // expression. We already checked that ShlAmt < BitWidth, so | |||
| 7003 | // the multiplier, 1 << (ShlAmt - AShrAmt), fits into TruncTy as | |||
| 7004 | // ShlAmt - AShrAmt < Amt. | |||
| 7005 | APInt Mul = APInt::getOneBitSet(BitWidth - AShrAmt, | |||
| 7006 | ShlAmt - AShrAmt); | |||
| 7007 | return getSignExtendExpr( | |||
| 7008 | getMulExpr(getTruncateExpr(ShlOp0SCEV, TruncTy), | |||
| 7009 | getConstant(Mul)), OuterTy); | |||
| 7010 | } | |||
| 7011 | } | |||
| 7012 | } | |||
| 7013 | break; | |||
| 7014 | } | |||
| 7015 | } | |||
| 7016 | } | |||
| 7017 | ||||
| 7018 | switch (U->getOpcode()) { | |||
| 7019 | case Instruction::Trunc: | |||
| 7020 | return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType()); | |||
| 7021 | ||||
| 7022 | case Instruction::ZExt: | |||
| 7023 | return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType()); | |||
| 7024 | ||||
| 7025 | case Instruction::SExt: | |||
| 7026 | if (auto BO = MatchBinaryOp(U->getOperand(0), DT)) { | |||
| 7027 | // The NSW flag of a subtract does not always survive the conversion to | |||
| 7028 | // A + (-1)*B. By pushing sign extension onto its operands we are much | |||
| 7029 | // more likely to preserve NSW and allow later AddRec optimisations. | |||
| 7030 | // | |||
| 7031 | // NOTE: This is effectively duplicating this logic from getSignExtend: | |||
| 7032 | // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw> | |||
| 7033 | // but by that point the NSW information has potentially been lost. | |||
| 7034 | if (BO->Opcode == Instruction::Sub && BO->IsNSW) { | |||
| 7035 | Type *Ty = U->getType(); | |||
| 7036 | auto *V1 = getSignExtendExpr(getSCEV(BO->LHS), Ty); | |||
| 7037 | auto *V2 = getSignExtendExpr(getSCEV(BO->RHS), Ty); | |||
| 7038 | return getMinusSCEV(V1, V2, SCEV::FlagNSW); | |||
| 7039 | } | |||
| 7040 | } | |||
| 7041 | return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType()); | |||
| 7042 | ||||
| 7043 | case Instruction::BitCast: | |||
| 7044 | // BitCasts are no-op casts so we just eliminate the cast. | |||
| 7045 | if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType())) | |||
| 7046 | return getSCEV(U->getOperand(0)); | |||
| 7047 | break; | |||
| 7048 | ||||
| 7049 | case Instruction::PtrToInt: { | |||
| 7050 | // Pointer to integer cast is straight-forward, so do model it. | |||
| 7051 | const SCEV *Op = getSCEV(U->getOperand(0)); | |||
| 7052 | Type *DstIntTy = U->getType(); | |||
| 7053 | // But only if effective SCEV (integer) type is wide enough to represent | |||
| 7054 | // all possible pointer values. | |||
| 7055 | const SCEV *IntOp = getPtrToIntExpr(Op, DstIntTy); | |||
| 7056 | if (isa<SCEVCouldNotCompute>(IntOp)) | |||
| 7057 | return getUnknown(V); | |||
| 7058 | return IntOp; | |||
| 7059 | } | |||
| 7060 | case Instruction::IntToPtr: | |||
| 7061 | // Just don't deal with inttoptr casts. | |||
| 7062 | return getUnknown(V); | |||
| 7063 | ||||
| 7064 | case Instruction::SDiv: | |||
| 7065 | // If both operands are non-negative, this is just an udiv. | |||
| 7066 | if (isKnownNonNegative(getSCEV(U->getOperand(0))) && | |||
| 7067 | isKnownNonNegative(getSCEV(U->getOperand(1)))) | |||
| 7068 | return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1))); | |||
| 7069 | break; | |||
| 7070 | ||||
| 7071 | case Instruction::SRem: | |||
| 7072 | // If both operands are non-negative, this is just an urem. | |||
| 7073 | if (isKnownNonNegative(getSCEV(U->getOperand(0))) && | |||
| 7074 | isKnownNonNegative(getSCEV(U->getOperand(1)))) | |||
| 7075 | return getURemExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1))); | |||
| 7076 | break; | |||
| 7077 | ||||
| 7078 | case Instruction::GetElementPtr: | |||
| 7079 | return createNodeForGEP(cast<GEPOperator>(U)); | |||
| 7080 | ||||
| 7081 | case Instruction::PHI: | |||
| 7082 | return createNodeForPHI(cast<PHINode>(U)); | |||
| 7083 | ||||
| 7084 | case Instruction::Select: | |||
| 7085 | // U can also be a select constant expr, which let fall through. Since | |||
| 7086 | // createNodeForSelect only works for a condition that is an `ICmpInst`, and | |||
| 7087 | // constant expressions cannot have instructions as operands, we'd have | |||
| 7088 | // returned getUnknown for a select constant expressions anyway. | |||
| 7089 | if (isa<Instruction>(U)) | |||
| 7090 | return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0), | |||
| 7091 | U->getOperand(1), U->getOperand(2)); | |||
| 7092 | break; | |||
| 7093 | ||||
| 7094 | case Instruction::Call: | |||
| 7095 | case Instruction::Invoke: | |||
| 7096 | if (Value *RV = cast<CallBase>(U)->getReturnedArgOperand()) | |||
| 7097 | return getSCEV(RV); | |||
| 7098 | ||||
| 7099 | if (auto *II = dyn_cast<IntrinsicInst>(U)) { | |||
| 7100 | switch (II->getIntrinsicID()) { | |||
| 7101 | case Intrinsic::abs: | |||
| 7102 | return getAbsExpr( | |||
| 7103 | getSCEV(II->getArgOperand(0)), | |||
| 7104 | /*IsNSW=*/cast<ConstantInt>(II->getArgOperand(1))->isOne()); | |||
| 7105 | case Intrinsic::umax: | |||
| 7106 | return getUMaxExpr(getSCEV(II->getArgOperand(0)), | |||
| 7107 | getSCEV(II->getArgOperand(1))); | |||
| 7108 | case Intrinsic::umin: | |||
| 7109 | return getUMinExpr(getSCEV(II->getArgOperand(0)), | |||
| 7110 | getSCEV(II->getArgOperand(1))); | |||
| 7111 | case Intrinsic::smax: | |||
| 7112 | return getSMaxExpr(getSCEV(II->getArgOperand(0)), | |||
| 7113 | getSCEV(II->getArgOperand(1))); | |||
| 7114 | case Intrinsic::smin: | |||
| 7115 | return getSMinExpr(getSCEV(II->getArgOperand(0)), | |||
| 7116 | getSCEV(II->getArgOperand(1))); | |||
| 7117 | case Intrinsic::usub_sat: { | |||
| 7118 | const SCEV *X = getSCEV(II->getArgOperand(0)); | |||
| 7119 | const SCEV *Y = getSCEV(II->getArgOperand(1)); | |||
| 7120 | const SCEV *ClampedY = getUMinExpr(X, Y); | |||
| 7121 | return getMinusSCEV(X, ClampedY, SCEV::FlagNUW); | |||
| 7122 | } | |||
| 7123 | case Intrinsic::uadd_sat: { | |||
| 7124 | const SCEV *X = getSCEV(II->getArgOperand(0)); | |||
| 7125 | const SCEV *Y = getSCEV(II->getArgOperand(1)); | |||
| 7126 | const SCEV *ClampedX = getUMinExpr(X, getNotSCEV(Y)); | |||
| 7127 | return getAddExpr(ClampedX, Y, SCEV::FlagNUW); | |||
| 7128 | } | |||
| 7129 | case Intrinsic::start_loop_iterations: | |||
| 7130 | // A start_loop_iterations is just equivalent to the first operand for | |||
| 7131 | // SCEV purposes. | |||
| 7132 | return getSCEV(II->getArgOperand(0)); | |||
| 7133 | default: | |||
| 7134 | break; | |||
| 7135 | } | |||
| 7136 | } | |||
| 7137 | break; | |||
| 7138 | } | |||
| 7139 | ||||
| 7140 | return getUnknown(V); | |||
| 7141 | } | |||
| 7142 | ||||
| 7143 | //===----------------------------------------------------------------------===// | |||
| 7144 | // Iteration Count Computation Code | |||
| 7145 | // | |||
| 7146 | ||||
| 7147 | const SCEV *ScalarEvolution::getTripCountFromExitCount(const SCEV *ExitCount) { | |||
| 7148 | // Get the trip count from the BE count by adding 1. Overflow, results | |||
| 7149 | // in zero which means "unknown". | |||
| 7150 | return getAddExpr(ExitCount, getOne(ExitCount->getType())); | |||
| 7151 | } | |||
| 7152 | ||||
| 7153 | static unsigned getConstantTripCount(const SCEVConstant *ExitCount) { | |||
| 7154 | if (!ExitCount) | |||
| 7155 | return 0; | |||
| 7156 | ||||
| 7157 | ConstantInt *ExitConst = ExitCount->getValue(); | |||
| 7158 | ||||
| 7159 | // Guard against huge trip counts. | |||
| 7160 | if (ExitConst->getValue().getActiveBits() > 32) | |||
| 7161 | return 0; | |||
| 7162 | ||||
| 7163 | // In case of integer overflow, this returns 0, which is correct. | |||
| 7164 | return ((unsigned)ExitConst->getZExtValue()) + 1; | |||
| 7165 | } | |||
| 7166 | ||||
| 7167 | unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L) { | |||
| 7168 | auto *ExitCount = dyn_cast<SCEVConstant>(getBackedgeTakenCount(L, Exact)); | |||
| 7169 | return getConstantTripCount(ExitCount); | |||
| 7170 | } | |||
| 7171 | ||||
| 7172 | unsigned | |||
| 7173 | ScalarEvolution::getSmallConstantTripCount(const Loop *L, | |||
| 7174 | const BasicBlock *ExitingBlock) { | |||
| 7175 | assert(ExitingBlock && "Must pass a non-null exiting block!")((void)0); | |||
| 7176 | assert(L->isLoopExiting(ExitingBlock) &&((void)0) | |||
| 7177 | "Exiting block must actually branch out of the loop!")((void)0); | |||
| 7178 | const SCEVConstant *ExitCount = | |||
| 7179 | dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock)); | |||
| 7180 | return getConstantTripCount(ExitCount); | |||
| 7181 | } | |||
| 7182 | ||||
| 7183 | unsigned ScalarEvolution::getSmallConstantMaxTripCount(const Loop *L) { | |||
| 7184 | const auto *MaxExitCount = | |||
| 7185 | dyn_cast<SCEVConstant>(getConstantMaxBackedgeTakenCount(L)); | |||
| 7186 | return getConstantTripCount(MaxExitCount); | |||
| 7187 | } | |||
| 7188 | ||||
| 7189 | unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L) { | |||
| 7190 | SmallVector<BasicBlock *, 8> ExitingBlocks; | |||
| 7191 | L->getExitingBlocks(ExitingBlocks); | |||
| 7192 | ||||
| 7193 | Optional<unsigned> Res = None; | |||
| 7194 | for (auto *ExitingBB : ExitingBlocks) { | |||
| 7195 | unsigned Multiple = getSmallConstantTripMultiple(L, ExitingBB); | |||
| 7196 | if (!Res) | |||
| 7197 | Res = Multiple; | |||
| 7198 | Res = (unsigned)GreatestCommonDivisor64(*Res, Multiple); | |||
| 7199 | } | |||
| 7200 | return Res.getValueOr(1); | |||
| 7201 | } | |||
| 7202 | ||||
| 7203 | unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L, | |||
| 7204 | const SCEV *ExitCount) { | |||
| 7205 | if (ExitCount == getCouldNotCompute()) | |||
| 7206 | return 1; | |||
| 7207 | ||||
| 7208 | // Get the trip count | |||
| 7209 | const SCEV *TCExpr = getTripCountFromExitCount(ExitCount); | |||
| 7210 | ||||
| 7211 | const SCEVConstant *TC = dyn_cast<SCEVConstant>(TCExpr); | |||
| 7212 | if (!TC) | |||
| 7213 | // Attempt to factor more general cases. Returns the greatest power of | |||
| 7214 | // two divisor. If overflow happens, the trip count expression is still | |||
| 7215 | // divisible by the greatest power of 2 divisor returned. | |||
| 7216 | return 1U << std::min((uint32_t)31, | |||
| 7217 | GetMinTrailingZeros(applyLoopGuards(TCExpr, L))); | |||
| 7218 | ||||
| 7219 | ConstantInt *Result = TC->getValue(); | |||
| 7220 | ||||
| 7221 | // Guard against huge trip counts (this requires checking | |||
| 7222 | // for zero to handle the case where the trip count == -1 and the | |||
| 7223 | // addition wraps). | |||
| 7224 | if (!Result || Result->getValue().getActiveBits() > 32 || | |||
| 7225 | Result->getValue().getActiveBits() == 0) | |||
| 7226 | return 1; | |||
| 7227 | ||||
| 7228 | return (unsigned)Result->getZExtValue(); | |||
| 7229 | } | |||
| 7230 | ||||
| 7231 | /// Returns the largest constant divisor of the trip count of this loop as a | |||
| 7232 | /// normal unsigned value, if possible. This means that the actual trip count is | |||
| 7233 | /// always a multiple of the returned value (don't forget the trip count could | |||
| 7234 | /// very well be zero as well!). | |||
| 7235 | /// | |||
| 7236 | /// Returns 1 if the trip count is unknown or not guaranteed to be the | |||
| 7237 | /// multiple of a constant (which is also the case if the trip count is simply | |||
| 7238 | /// constant, use getSmallConstantTripCount for that case), Will also return 1 | |||
| 7239 | /// if the trip count is very large (>= 2^32). | |||
| 7240 | /// | |||
| 7241 | /// As explained in the comments for getSmallConstantTripCount, this assumes | |||
| 7242 | /// that control exits the loop via ExitingBlock. | |||
| 7243 | unsigned | |||
| 7244 | ScalarEvolution::getSmallConstantTripMultiple(const Loop *L, | |||
| 7245 | const BasicBlock *ExitingBlock) { | |||
| 7246 | assert(ExitingBlock && "Must pass a non-null exiting block!")((void)0); | |||
| 7247 | assert(L->isLoopExiting(ExitingBlock) &&((void)0) | |||
| 7248 | "Exiting block must actually branch out of the loop!")((void)0); | |||
| 7249 | const SCEV *ExitCount = getExitCount(L, ExitingBlock); | |||
| 7250 | return getSmallConstantTripMultiple(L, ExitCount); | |||
| 7251 | } | |||
| 7252 | ||||
| 7253 | const SCEV *ScalarEvolution::getExitCount(const Loop *L, | |||
| 7254 | const BasicBlock *ExitingBlock, | |||
| 7255 | ExitCountKind Kind) { | |||
| 7256 | switch (Kind) { | |||
| 7257 | case Exact: | |||
| 7258 | case SymbolicMaximum: | |||
| 7259 | return getBackedgeTakenInfo(L).getExact(ExitingBlock, this); | |||
| 7260 | case ConstantMaximum: | |||
| 7261 | return getBackedgeTakenInfo(L).getConstantMax(ExitingBlock, this); | |||
| 7262 | }; | |||
| 7263 | llvm_unreachable("Invalid ExitCountKind!")__builtin_unreachable(); | |||
| 7264 | } | |||
| 7265 | ||||
| 7266 | const SCEV * | |||
| 7267 | ScalarEvolution::getPredicatedBackedgeTakenCount(const Loop *L, | |||
| 7268 | SCEVUnionPredicate &Preds) { | |||
| 7269 | return getPredicatedBackedgeTakenInfo(L).getExact(L, this, &Preds); | |||
| 7270 | } | |||
| 7271 | ||||
| 7272 | const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L, | |||
| 7273 | ExitCountKind Kind) { | |||
| 7274 | switch (Kind) { | |||
| 7275 | case Exact: | |||
| 7276 | return getBackedgeTakenInfo(L).getExact(L, this); | |||
| 7277 | case ConstantMaximum: | |||
| 7278 | return getBackedgeTakenInfo(L).getConstantMax(this); | |||
| 7279 | case SymbolicMaximum: | |||
| 7280 | return getBackedgeTakenInfo(L).getSymbolicMax(L, this); | |||
| 7281 | }; | |||
| 7282 | llvm_unreachable("Invalid ExitCountKind!")__builtin_unreachable(); | |||
| 7283 | } | |||
| 7284 | ||||
| 7285 | bool ScalarEvolution::isBackedgeTakenCountMaxOrZero(const Loop *L) { | |||
| 7286 | return getBackedgeTakenInfo(L).isConstantMaxOrZero(this); | |||
| 7287 | } | |||
| 7288 | ||||
| 7289 | /// Push PHI nodes in the header of the given loop onto the given Worklist. | |||
| 7290 | static void | |||
| 7291 | PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) { | |||
| 7292 | BasicBlock *Header = L->getHeader(); | |||
| 7293 | ||||
| 7294 | // Push all Loop-header PHIs onto the Worklist stack. | |||
| 7295 | for (PHINode &PN : Header->phis()) | |||
| 7296 | Worklist.push_back(&PN); | |||
| 7297 | } | |||
| 7298 | ||||
| 7299 | const ScalarEvolution::BackedgeTakenInfo & | |||
| 7300 | ScalarEvolution::getPredicatedBackedgeTakenInfo(const Loop *L) { | |||
| 7301 | auto &BTI = getBackedgeTakenInfo(L); | |||
| 7302 | if (BTI.hasFullInfo()) | |||
| 7303 | return BTI; | |||
| 7304 | ||||
| 7305 | auto Pair = PredicatedBackedgeTakenCounts.insert({L, BackedgeTakenInfo()}); | |||
| 7306 | ||||
| 7307 | if (!Pair.second) | |||
| 7308 | return Pair.first->second; | |||
| 7309 | ||||
| 7310 | BackedgeTakenInfo Result = | |||
| 7311 | computeBackedgeTakenCount(L, /*AllowPredicates=*/true); | |||
| 7312 | ||||
| 7313 | return PredicatedBackedgeTakenCounts.find(L)->second = std::move(Result); | |||
| 7314 | } | |||
| 7315 | ||||
| 7316 | ScalarEvolution::BackedgeTakenInfo & | |||
| 7317 | ScalarEvolution::getBackedgeTakenInfo(const Loop *L) { | |||
| 7318 | // Initially insert an invalid entry for this loop. If the insertion | |||
| 7319 | // succeeds, proceed to actually compute a backedge-taken count and | |||
| 7320 | // update the value. The temporary CouldNotCompute value tells SCEV | |||
| 7321 | // code elsewhere that it shouldn't attempt to request a new | |||
| 7322 | // backedge-taken count, which could result in infinite recursion. | |||
| 7323 | std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair = | |||
| 7324 | BackedgeTakenCounts.insert({L, BackedgeTakenInfo()}); | |||
| 7325 | if (!Pair.second) | |||
| 7326 | return Pair.first->second; | |||
| 7327 | ||||
| 7328 | // computeBackedgeTakenCount may allocate memory for its result. Inserting it | |||
| 7329 | // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result | |||
| 7330 | // must be cleared in this scope. | |||
| 7331 | BackedgeTakenInfo Result = computeBackedgeTakenCount(L); | |||
| 7332 | ||||
| 7333 | // In product build, there are no usage of statistic. | |||
| 7334 | (void)NumTripCountsComputed; | |||
| 7335 | (void)NumTripCountsNotComputed; | |||
| 7336 | #if LLVM_ENABLE_STATS0 || !defined(NDEBUG1) | |||
| 7337 | const SCEV *BEExact = Result.getExact(L, this); | |||
| 7338 | if (BEExact != getCouldNotCompute()) { | |||
| 7339 | assert(isLoopInvariant(BEExact, L) &&((void)0) | |||
| 7340 | isLoopInvariant(Result.getConstantMax(this), L) &&((void)0) | |||
| 7341 | "Computed backedge-taken count isn't loop invariant for loop!")((void)0); | |||
| 7342 | ++NumTripCountsComputed; | |||
| 7343 | } else if (Result.getConstantMax(this) == getCouldNotCompute() && | |||
| 7344 | isa<PHINode>(L->getHeader()->begin())) { | |||
| 7345 | // Only count loops that have phi nodes as not being computable. | |||
| 7346 | ++NumTripCountsNotComputed; | |||
| 7347 | } | |||
| 7348 | #endif // LLVM_ENABLE_STATS || !defined(NDEBUG) | |||
| 7349 | ||||
| 7350 | // Now that we know more about the trip count for this loop, forget any | |||
| 7351 | // existing SCEV values for PHI nodes in this loop since they are only | |||
| 7352 | // conservative estimates made without the benefit of trip count | |||
| 7353 | // information. This is similar to the code in forgetLoop, except that | |||
| 7354 | // it handles SCEVUnknown PHI nodes specially. | |||
| 7355 | if (Result.hasAnyInfo()) { | |||
| 7356 | SmallVector<Instruction *, 16> Worklist; | |||
| 7357 | PushLoopPHIs(L, Worklist); | |||
| 7358 | ||||
| 7359 | SmallPtrSet<Instruction *, 8> Discovered; | |||
| 7360 | while (!Worklist.empty()) { | |||
| 7361 | Instruction *I = Worklist.pop_back_val(); | |||
| 7362 | ||||
| 7363 | ValueExprMapType::iterator It = | |||
| 7364 | ValueExprMap.find_as(static_cast<Value *>(I)); | |||
| 7365 | if (It != ValueExprMap.end()) { | |||
| 7366 | const SCEV *Old = It->second; | |||
| 7367 | ||||
| 7368 | // SCEVUnknown for a PHI either means that it has an unrecognized | |||
| 7369 | // structure, or it's a PHI that's in the progress of being computed | |||
| 7370 | // by createNodeForPHI. In the former case, additional loop trip | |||
| 7371 | // count information isn't going to change anything. In the later | |||
| 7372 | // case, createNodeForPHI will perform the necessary updates on its | |||
| 7373 | // own when it gets to that point. | |||
| 7374 | if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) { | |||
| 7375 | eraseValueFromMap(It->first); | |||
| 7376 | forgetMemoizedResults(Old); | |||
| 7377 | } | |||
| 7378 | if (PHINode *PN = dyn_cast<PHINode>(I)) | |||
| 7379 | ConstantEvolutionLoopExitValue.erase(PN); | |||
| 7380 | } | |||
| 7381 | ||||
| 7382 | // Since we don't need to invalidate anything for correctness and we're | |||
| 7383 | // only invalidating to make SCEV's results more precise, we get to stop | |||
| 7384 | // early to avoid invalidating too much. This is especially important in | |||
| 7385 | // cases like: | |||
| 7386 | // | |||
| 7387 | // %v = f(pn0, pn1) // pn0 and pn1 used through some other phi node | |||
| 7388 | // loop0: | |||
| 7389 | // %pn0 = phi | |||
| 7390 | // ... | |||
| 7391 | // loop1: | |||
| 7392 | // %pn1 = phi | |||
| 7393 | // ... | |||
| 7394 | // | |||
| 7395 | // where both loop0 and loop1's backedge taken count uses the SCEV | |||
| 7396 | // expression for %v. If we don't have the early stop below then in cases | |||
| 7397 | // like the above, getBackedgeTakenInfo(loop1) will clear out the trip | |||
| 7398 | // count for loop0 and getBackedgeTakenInfo(loop0) will clear out the trip | |||
| 7399 | // count for loop1, effectively nullifying SCEV's trip count cache. | |||
| 7400 | for (auto *U : I->users()) | |||
| 7401 | if (auto *I = dyn_cast<Instruction>(U)) { | |||
| 7402 | auto *LoopForUser = LI.getLoopFor(I->getParent()); | |||
| 7403 | if (LoopForUser && L->contains(LoopForUser) && | |||
| 7404 | Discovered.insert(I).second) | |||
| 7405 | Worklist.push_back(I); | |||
| 7406 | } | |||
| 7407 | } | |||
| 7408 | } | |||
| 7409 | ||||
| 7410 | // Re-lookup the insert position, since the call to | |||
| 7411 | // computeBackedgeTakenCount above could result in a | |||
| 7412 | // recusive call to getBackedgeTakenInfo (on a different | |||
| 7413 | // loop), which would invalidate the iterator computed | |||
| 7414 | // earlier. | |||
| 7415 | return BackedgeTakenCounts.find(L)->second = std::move(Result); | |||
| 7416 | } | |||
| 7417 | ||||
| 7418 | void ScalarEvolution::forgetAllLoops() { | |||
| 7419 | // This method is intended to forget all info about loops. It should | |||
| 7420 | // invalidate caches as if the following happened: | |||
| 7421 | // - The trip counts of all loops have changed arbitrarily | |||
| 7422 | // - Every llvm::Value has been updated in place to produce a different | |||
| 7423 | // result. | |||
| 7424 | BackedgeTakenCounts.clear(); | |||
| 7425 | PredicatedBackedgeTakenCounts.clear(); | |||
| 7426 | LoopPropertiesCache.clear(); | |||
| 7427 | ConstantEvolutionLoopExitValue.clear(); | |||
| 7428 | ValueExprMap.clear(); | |||
| 7429 | ValuesAtScopes.clear(); | |||
| 7430 | LoopDispositions.clear(); | |||
| 7431 | BlockDispositions.clear(); | |||
| 7432 | UnsignedRanges.clear(); | |||
| 7433 | SignedRanges.clear(); | |||
| 7434 | ExprValueMap.clear(); | |||
| 7435 | HasRecMap.clear(); | |||
| 7436 | MinTrailingZerosCache.clear(); | |||
| 7437 | PredicatedSCEVRewrites.clear(); | |||
| 7438 | } | |||
| 7439 | ||||
| 7440 | void ScalarEvolution::forgetLoop(const Loop *L) { | |||
| 7441 | SmallVector<const Loop *, 16> LoopWorklist(1, L); | |||
| 7442 | SmallVector<Instruction *, 32> Worklist; | |||
| 7443 | SmallPtrSet<Instruction *, 16> Visited; | |||
| 7444 | ||||
| 7445 | // Iterate over all the loops and sub-loops to drop SCEV information. | |||
| 7446 | while (!LoopWorklist.empty()) { | |||
| 7447 | auto *CurrL = LoopWorklist.pop_back_val(); | |||
| 7448 | ||||
| 7449 | // Drop any stored trip count value. | |||
| 7450 | BackedgeTakenCounts.erase(CurrL); | |||
| 7451 | PredicatedBackedgeTakenCounts.erase(CurrL); | |||
| 7452 | ||||
| 7453 | // Drop information about predicated SCEV rewrites for this loop. | |||
| 7454 | for (auto I = PredicatedSCEVRewrites.begin(); | |||
| 7455 | I != PredicatedSCEVRewrites.end();) { | |||
| 7456 | std::pair<const SCEV *, const Loop *> Entry = I->first; | |||
| 7457 | if (Entry.second == CurrL) | |||
| 7458 | PredicatedSCEVRewrites.erase(I++); | |||
| 7459 | else | |||
| 7460 | ++I; | |||
| 7461 | } | |||
| 7462 | ||||
| 7463 | auto LoopUsersItr = LoopUsers.find(CurrL); | |||
| 7464 | if (LoopUsersItr != LoopUsers.end()) { | |||
| 7465 | for (auto *S : LoopUsersItr->second) | |||
| 7466 | forgetMemoizedResults(S); | |||
| 7467 | LoopUsers.erase(LoopUsersItr); | |||
| 7468 | } | |||
| 7469 | ||||
| 7470 | // Drop information about expressions based on loop-header PHIs. | |||
| 7471 | PushLoopPHIs(CurrL, Worklist); | |||
| 7472 | ||||
| 7473 | while (!Worklist.empty()) { | |||
| 7474 | Instruction *I = Worklist.pop_back_val(); | |||
| 7475 | if (!Visited.insert(I).second) | |||
| 7476 | continue; | |||
| 7477 | ||||
| 7478 | ValueExprMapType::iterator It = | |||
| 7479 | ValueExprMap.find_as(static_cast<Value *>(I)); | |||
| 7480 | if (It != ValueExprMap.end()) { | |||
| 7481 | eraseValueFromMap(It->first); | |||
| 7482 | forgetMemoizedResults(It->second); | |||
| 7483 | if (PHINode *PN = dyn_cast<PHINode>(I)) | |||
| 7484 | ConstantEvolutionLoopExitValue.erase(PN); | |||
| 7485 | } | |||
| 7486 | ||||
| 7487 | PushDefUseChildren(I, Worklist); | |||
| 7488 | } | |||
| 7489 | ||||
| 7490 | LoopPropertiesCache.erase(CurrL); | |||
| 7491 | // Forget all contained loops too, to avoid dangling entries in the | |||
| 7492 | // ValuesAtScopes map. | |||
| 7493 | LoopWorklist.append(CurrL->begin(), CurrL->end()); | |||
| 7494 | } | |||
| 7495 | } | |||
| 7496 | ||||
| 7497 | void ScalarEvolution::forgetTopmostLoop(const Loop *L) { | |||
| 7498 | while (Loop *Parent = L->getParentLoop()) | |||
| 7499 | L = Parent; | |||
| 7500 | forgetLoop(L); | |||
| 7501 | } | |||
| 7502 | ||||
| 7503 | void ScalarEvolution::forgetValue(Value *V) { | |||
| 7504 | Instruction *I = dyn_cast<Instruction>(V); | |||
| 7505 | if (!I) return; | |||
| 7506 | ||||
| 7507 | // Drop information about expressions based on loop-header PHIs. | |||
| 7508 | SmallVector<Instruction *, 16> Worklist; | |||
| 7509 | Worklist.push_back(I); | |||
| 7510 | ||||
| 7511 | SmallPtrSet<Instruction *, 8> Visited; | |||
| 7512 | while (!Worklist.empty()) { | |||
| 7513 | I = Worklist.pop_back_val(); | |||
| 7514 | if (!Visited.insert(I).second) | |||
| 7515 | continue; | |||
| 7516 | ||||
| 7517 | ValueExprMapType::iterator It = | |||
| 7518 | ValueExprMap.find_as(static_cast<Value *>(I)); | |||
| 7519 | if (It != ValueExprMap.end()) { | |||
| 7520 | eraseValueFromMap(It->first); | |||
| 7521 | forgetMemoizedResults(It->second); | |||
| 7522 | if (PHINode *PN = dyn_cast<PHINode>(I)) | |||
| 7523 | ConstantEvolutionLoopExitValue.erase(PN); | |||
| 7524 | } | |||
| 7525 | ||||
| 7526 | PushDefUseChildren(I, Worklist); | |||
| 7527 | } | |||
| 7528 | } | |||
| 7529 | ||||
| 7530 | void ScalarEvolution::forgetLoopDispositions(const Loop *L) { | |||
| 7531 | LoopDispositions.clear(); | |||
| 7532 | } | |||
| 7533 | ||||
| 7534 | /// Get the exact loop backedge taken count considering all loop exits. A | |||
| 7535 | /// computable result can only be returned for loops with all exiting blocks | |||
| 7536 | /// dominating the latch. howFarToZero assumes that the limit of each loop test | |||
| 7537 | /// is never skipped. This is a valid assumption as long as the loop exits via | |||
| 7538 | /// that test. For precise results, it is the caller's responsibility to specify | |||
| 7539 | /// the relevant loop exiting block using getExact(ExitingBlock, SE). | |||
| 7540 | const SCEV * | |||
| 7541 | ScalarEvolution::BackedgeTakenInfo::getExact(const Loop *L, ScalarEvolution *SE, | |||
| 7542 | SCEVUnionPredicate *Preds) const { | |||
| 7543 | // If any exits were not computable, the loop is not computable. | |||
| 7544 | if (!isComplete() || ExitNotTaken.empty()) | |||
| 7545 | return SE->getCouldNotCompute(); | |||
| 7546 | ||||
| 7547 | const BasicBlock *Latch = L->getLoopLatch(); | |||
| 7548 | // All exiting blocks we have collected must dominate the only backedge. | |||
| 7549 | if (!Latch) | |||
| 7550 | return SE->getCouldNotCompute(); | |||
| 7551 | ||||
| 7552 | // All exiting blocks we have gathered dominate loop's latch, so exact trip | |||
| 7553 | // count is simply a minimum out of all these calculated exit counts. | |||
| 7554 | SmallVector<const SCEV *, 2> Ops; | |||
| 7555 | for (auto &ENT : ExitNotTaken) { | |||
| 7556 | const SCEV *BECount = ENT.ExactNotTaken; | |||
| 7557 | assert(BECount != SE->getCouldNotCompute() && "Bad exit SCEV!")((void)0); | |||
| 7558 | assert(SE->DT.dominates(ENT.ExitingBlock, Latch) &&((void)0) | |||
| 7559 | "We should only have known counts for exiting blocks that dominate "((void)0) | |||
| 7560 | "latch!")((void)0); | |||
| 7561 | ||||
| 7562 | Ops.push_back(BECount); | |||
| 7563 | ||||
| 7564 | if (Preds && !ENT.hasAlwaysTruePredicate()) | |||
| 7565 | Preds->add(ENT.Predicate.get()); | |||
| 7566 | ||||
| 7567 | assert((Preds || ENT.hasAlwaysTruePredicate()) &&((void)0) | |||
| 7568 | "Predicate should be always true!")((void)0); | |||
| 7569 | } | |||
| 7570 | ||||
| 7571 | return SE->getUMinFromMismatchedTypes(Ops); | |||
| 7572 | } | |||
| 7573 | ||||
| 7574 | /// Get the exact not taken count for this loop exit. | |||
| 7575 | const SCEV * | |||
| 7576 | ScalarEvolution::BackedgeTakenInfo::getExact(const BasicBlock *ExitingBlock, | |||
| 7577 | ScalarEvolution *SE) const { | |||
| 7578 | for (auto &ENT : ExitNotTaken) | |||
| 7579 | if (ENT.ExitingBlock == ExitingBlock && ENT.hasAlwaysTruePredicate()) | |||
| 7580 | return ENT.ExactNotTaken; | |||
| 7581 | ||||
| 7582 | return SE->getCouldNotCompute(); | |||
| 7583 | } | |||
| 7584 | ||||
| 7585 | const SCEV *ScalarEvolution::BackedgeTakenInfo::getConstantMax( | |||
| 7586 | const BasicBlock *ExitingBlock, ScalarEvolution *SE) const { | |||
| 7587 | for (auto &ENT : ExitNotTaken) | |||
| 7588 | if (ENT.ExitingBlock == ExitingBlock && ENT.hasAlwaysTruePredicate()) | |||
| 7589 | return ENT.MaxNotTaken; | |||
| 7590 | ||||
| 7591 | return SE->getCouldNotCompute(); | |||
| 7592 | } | |||
| 7593 | ||||
| 7594 | /// getConstantMax - Get the constant max backedge taken count for the loop. | |||
| 7595 | const SCEV * | |||
| 7596 | ScalarEvolution::BackedgeTakenInfo::getConstantMax(ScalarEvolution *SE) const { | |||
| 7597 | auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) { | |||
| 7598 | return !ENT.hasAlwaysTruePredicate(); | |||
| 7599 | }; | |||
| 7600 | ||||
| 7601 | if (any_of(ExitNotTaken, PredicateNotAlwaysTrue) || !getConstantMax()) | |||
| 7602 | return SE->getCouldNotCompute(); | |||
| 7603 | ||||
| 7604 | assert((isa<SCEVCouldNotCompute>(getConstantMax()) ||((void)0) | |||
| 7605 | isa<SCEVConstant>(getConstantMax())) &&((void)0) | |||
| 7606 | "No point in having a non-constant max backedge taken count!")((void)0); | |||
| 7607 | return getConstantMax(); | |||
| 7608 | } | |||
| 7609 | ||||
| 7610 | const SCEV * | |||
| 7611 | ScalarEvolution::BackedgeTakenInfo::getSymbolicMax(const Loop *L, | |||
| 7612 | ScalarEvolution *SE) { | |||
| 7613 | if (!SymbolicMax) | |||
| 7614 | SymbolicMax = SE->computeSymbolicMaxBackedgeTakenCount(L); | |||
| 7615 | return SymbolicMax; | |||
| 7616 | } | |||
| 7617 | ||||
| 7618 | bool ScalarEvolution::BackedgeTakenInfo::isConstantMaxOrZero( | |||
| 7619 | ScalarEvolution *SE) const { | |||
| 7620 | auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) { | |||
| 7621 | return !ENT.hasAlwaysTruePredicate(); | |||
| 7622 | }; | |||
| 7623 | return MaxOrZero && !any_of(ExitNotTaken, PredicateNotAlwaysTrue); | |||
| 7624 | } | |||
| 7625 | ||||
| 7626 | bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S) const { | |||
| 7627 | return Operands.contains(S); | |||
| 7628 | } | |||
| 7629 | ||||
| 7630 | ScalarEvolution::ExitLimit::ExitLimit(const SCEV *E) | |||
| 7631 | : ExitLimit(E, E, false, None) { | |||
| 7632 | } | |||
| 7633 | ||||
| 7634 | ScalarEvolution::ExitLimit::ExitLimit( | |||
| 7635 | const SCEV *E, const SCEV *M, bool MaxOrZero, | |||
| 7636 | ArrayRef<const SmallPtrSetImpl<const SCEVPredicate *> *> PredSetList) | |||
| 7637 | : ExactNotTaken(E), MaxNotTaken(M), MaxOrZero(MaxOrZero) { | |||
| 7638 | assert((isa<SCEVCouldNotCompute>(ExactNotTaken) ||((void)0) | |||
| 7639 | !isa<SCEVCouldNotCompute>(MaxNotTaken)) &&((void)0) | |||
| 7640 | "Exact is not allowed to be less precise than Max")((void)0); | |||
| 7641 | assert((isa<SCEVCouldNotCompute>(MaxNotTaken) ||((void)0) | |||
| 7642 | isa<SCEVConstant>(MaxNotTaken)) &&((void)0) | |||
| 7643 | "No point in having a non-constant max backedge taken count!")((void)0); | |||
| 7644 | for (auto *PredSet : PredSetList) | |||
| 7645 | for (auto *P : *PredSet) | |||
| 7646 | addPredicate(P); | |||
| 7647 | assert((isa<SCEVCouldNotCompute>(E) || !E->getType()->isPointerTy()) &&((void)0) | |||
| 7648 | "Backedge count should be int")((void)0); | |||
| 7649 | assert((isa<SCEVCouldNotCompute>(M) || !M->getType()->isPointerTy()) &&((void)0) | |||
| 7650 | "Max backedge count should be int")((void)0); | |||
| 7651 | } | |||
| 7652 | ||||
| 7653 | ScalarEvolution::ExitLimit::ExitLimit( | |||
| 7654 | const SCEV *E, const SCEV *M, bool MaxOrZero, | |||
| 7655 | const SmallPtrSetImpl<const SCEVPredicate *> &PredSet) | |||
| 7656 | : ExitLimit(E, M, MaxOrZero, {&PredSet}) { | |||
| 7657 | } | |||
| 7658 | ||||
| 7659 | ScalarEvolution::ExitLimit::ExitLimit(const SCEV *E, const SCEV *M, | |||
| 7660 | bool MaxOrZero) | |||
| 7661 | : ExitLimit(E, M, MaxOrZero, None) { | |||
| 7662 | } | |||
| 7663 | ||||
| 7664 | class SCEVRecordOperands { | |||
| 7665 | SmallPtrSetImpl<const SCEV *> &Operands; | |||
| 7666 | ||||
| 7667 | public: | |||
| 7668 | SCEVRecordOperands(SmallPtrSetImpl<const SCEV *> &Operands) | |||
| 7669 | : Operands(Operands) {} | |||
| 7670 | bool follow(const SCEV *S) { | |||
| 7671 | Operands.insert(S); | |||
| 7672 | return true; | |||
| 7673 | } | |||
| 7674 | bool isDone() { return false; } | |||
| 7675 | }; | |||
| 7676 | ||||
| 7677 | /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each | |||
| 7678 | /// computable exit into a persistent ExitNotTakenInfo array. | |||
| 7679 | ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo( | |||
| 7680 | ArrayRef<ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo> ExitCounts, | |||
| 7681 | bool IsComplete, const SCEV *ConstantMax, bool MaxOrZero) | |||
| 7682 | : ConstantMax(ConstantMax), IsComplete(IsComplete), MaxOrZero(MaxOrZero) { | |||
| 7683 | using EdgeExitInfo = ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo; | |||
| 7684 | ||||
| 7685 | ExitNotTaken.reserve(ExitCounts.size()); | |||
| 7686 | std::transform( | |||
| 7687 | ExitCounts.begin(), ExitCounts.end(), std::back_inserter(ExitNotTaken), | |||
| 7688 | [&](const EdgeExitInfo &EEI) { | |||
| 7689 | BasicBlock *ExitBB = EEI.first; | |||
| 7690 | const ExitLimit &EL = EEI.second; | |||
| 7691 | if (EL.Predicates.empty()) | |||
| 7692 | return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, EL.MaxNotTaken, | |||
| 7693 | nullptr); | |||
| 7694 | ||||
| 7695 | std::unique_ptr<SCEVUnionPredicate> Predicate(new SCEVUnionPredicate); | |||
| 7696 | for (auto *Pred : EL.Predicates) | |||
| 7697 | Predicate->add(Pred); | |||
| 7698 | ||||
| 7699 | return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, EL.MaxNotTaken, | |||
| 7700 | std::move(Predicate)); | |||
| 7701 | }); | |||
| 7702 | assert((isa<SCEVCouldNotCompute>(ConstantMax) ||((void)0) | |||
| 7703 | isa<SCEVConstant>(ConstantMax)) &&((void)0) | |||
| 7704 | "No point in having a non-constant max backedge taken count!")((void)0); | |||
| 7705 | ||||
| 7706 | SCEVRecordOperands RecordOperands(Operands); | |||
| 7707 | SCEVTraversal<SCEVRecordOperands> ST(RecordOperands); | |||
| 7708 | if (!isa<SCEVCouldNotCompute>(ConstantMax)) | |||
| 7709 | ST.visitAll(ConstantMax); | |||
| 7710 | for (auto &ENT : ExitNotTaken) | |||
| 7711 | if (!isa<SCEVCouldNotCompute>(ENT.ExactNotTaken)) | |||
| 7712 | ST.visitAll(ENT.ExactNotTaken); | |||
| 7713 | } | |||
| 7714 | ||||
| 7715 | /// Compute the number of times the backedge of the specified loop will execute. | |||
| 7716 | ScalarEvolution::BackedgeTakenInfo | |||
| 7717 | ScalarEvolution::computeBackedgeTakenCount(const Loop *L, | |||
| 7718 | bool AllowPredicates) { | |||
| 7719 | SmallVector<BasicBlock *, 8> ExitingBlocks; | |||
| 7720 | L->getExitingBlocks(ExitingBlocks); | |||
| 7721 | ||||
| 7722 | using EdgeExitInfo = ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo; | |||
| 7723 | ||||
| 7724 | SmallVector<EdgeExitInfo, 4> ExitCounts; | |||
| 7725 | bool CouldComputeBECount = true; | |||
| 7726 | BasicBlock *Latch = L->getLoopLatch(); // may be NULL. | |||
| 7727 | const SCEV *MustExitMaxBECount = nullptr; | |||
| 7728 | const SCEV *MayExitMaxBECount = nullptr; | |||
| 7729 | bool MustExitMaxOrZero = false; | |||
| 7730 | ||||
| 7731 | // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts | |||
| 7732 | // and compute maxBECount. | |||
| 7733 | // Do a union of all the predicates here. | |||
| 7734 | for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) { | |||
| 7735 | BasicBlock *ExitBB = ExitingBlocks[i]; | |||
| 7736 | ||||
| 7737 | // We canonicalize untaken exits to br (constant), ignore them so that | |||
| 7738 | // proving an exit untaken doesn't negatively impact our ability to reason | |||
| 7739 | // about the loop as whole. | |||
| 7740 | if (auto *BI = dyn_cast<BranchInst>(ExitBB->getTerminator())) | |||
| 7741 | if (auto *CI = dyn_cast<ConstantInt>(BI->getCondition())) { | |||
| 7742 | bool ExitIfTrue = !L->contains(BI->getSuccessor(0)); | |||
| 7743 | if ((ExitIfTrue && CI->isZero()) || (!ExitIfTrue && CI->isOne())) | |||
| 7744 | continue; | |||
| 7745 | } | |||
| 7746 | ||||
| 7747 | ExitLimit EL = computeExitLimit(L, ExitBB, AllowPredicates); | |||
| 7748 | ||||
| 7749 | assert((AllowPredicates || EL.Predicates.empty()) &&((void)0) | |||
| 7750 | "Predicated exit limit when predicates are not allowed!")((void)0); | |||
| 7751 | ||||
| 7752 | // 1. For each exit that can be computed, add an entry to ExitCounts. | |||
| 7753 | // CouldComputeBECount is true only if all exits can be computed. | |||
| 7754 | if (EL.ExactNotTaken == getCouldNotCompute()) | |||
| 7755 | // We couldn't compute an exact value for this exit, so | |||
| 7756 | // we won't be able to compute an exact value for the loop. | |||
| 7757 | CouldComputeBECount = false; | |||
| 7758 | else | |||
| 7759 | ExitCounts.emplace_back(ExitBB, EL); | |||
| 7760 | ||||
| 7761 | // 2. Derive the loop's MaxBECount from each exit's max number of | |||
| 7762 | // non-exiting iterations. Partition the loop exits into two kinds: | |||
| 7763 | // LoopMustExits and LoopMayExits. | |||
| 7764 | // | |||
| 7765 | // If the exit dominates the loop latch, it is a LoopMustExit otherwise it | |||
| 7766 | // is a LoopMayExit. If any computable LoopMustExit is found, then | |||
| 7767 | // MaxBECount is the minimum EL.MaxNotTaken of computable | |||
| 7768 | // LoopMustExits. Otherwise, MaxBECount is conservatively the maximum | |||
| 7769 | // EL.MaxNotTaken, where CouldNotCompute is considered greater than any | |||
| 7770 | // computable EL.MaxNotTaken. | |||
| 7771 | if (EL.MaxNotTaken != getCouldNotCompute() && Latch && | |||
| 7772 | DT.dominates(ExitBB, Latch)) { | |||
| 7773 | if (!MustExitMaxBECount) { | |||
| 7774 | MustExitMaxBECount = EL.MaxNotTaken; | |||
| 7775 | MustExitMaxOrZero = EL.MaxOrZero; | |||
| 7776 | } else { | |||
| 7777 | MustExitMaxBECount = | |||
| 7778 | getUMinFromMismatchedTypes(MustExitMaxBECount, EL.MaxNotTaken); | |||
| 7779 | } | |||
| 7780 | } else if (MayExitMaxBECount != getCouldNotCompute()) { | |||
| 7781 | if (!MayExitMaxBECount || EL.MaxNotTaken == getCouldNotCompute()) | |||
| 7782 | MayExitMaxBECount = EL.MaxNotTaken; | |||
| 7783 | else { | |||
| 7784 | MayExitMaxBECount = | |||
| 7785 | getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.MaxNotTaken); | |||
| 7786 | } | |||
| 7787 | } | |||
| 7788 | } | |||
| 7789 | const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount : | |||
| 7790 | (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute()); | |||
| 7791 | // The loop backedge will be taken the maximum or zero times if there's | |||
| 7792 | // a single exit that must be taken the maximum or zero times. | |||
| 7793 | bool MaxOrZero = (MustExitMaxOrZero && ExitingBlocks.size() == 1); | |||
| 7794 | return BackedgeTakenInfo(std::move(ExitCounts), CouldComputeBECount, | |||
| 7795 | MaxBECount, MaxOrZero); | |||
| 7796 | } | |||
| 7797 | ||||
| 7798 | ScalarEvolution::ExitLimit | |||
| 7799 | ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock, | |||
| 7800 | bool AllowPredicates) { | |||
| 7801 | assert(L->contains(ExitingBlock) && "Exit count for non-loop block?")((void)0); | |||
| 7802 | // If our exiting block does not dominate the latch, then its connection with | |||
| 7803 | // loop's exit limit may be far from trivial. | |||
| 7804 | const BasicBlock *Latch = L->getLoopLatch(); | |||
| 7805 | if (!Latch || !DT.dominates(ExitingBlock, Latch)) | |||
| 7806 | return getCouldNotCompute(); | |||
| 7807 | ||||
| 7808 | bool IsOnlyExit = (L->getExitingBlock() != nullptr); | |||
| 7809 | Instruction *Term = ExitingBlock->getTerminator(); | |||
| 7810 | if (BranchInst *BI = dyn_cast<BranchInst>(Term)) { | |||
| 7811 | assert(BI->isConditional() && "If unconditional, it can't be in loop!")((void)0); | |||
| 7812 | bool ExitIfTrue = !L->contains(BI->getSuccessor(0)); | |||
| 7813 | assert(ExitIfTrue == L->contains(BI->getSuccessor(1)) &&((void)0) | |||
| 7814 | "It should have one successor in loop and one exit block!")((void)0); | |||
| 7815 | // Proceed to the next level to examine the exit condition expression. | |||
| 7816 | return computeExitLimitFromCond( | |||
| 7817 | L, BI->getCondition(), ExitIfTrue, | |||
| 7818 | /*ControlsExit=*/IsOnlyExit, AllowPredicates); | |||
| 7819 | } | |||
| 7820 | ||||
| 7821 | if (SwitchInst *SI = dyn_cast<SwitchInst>(Term)) { | |||
| 7822 | // For switch, make sure that there is a single exit from the loop. | |||
| 7823 | BasicBlock *Exit = nullptr; | |||
| 7824 | for (auto *SBB : successors(ExitingBlock)) | |||
| 7825 | if (!L->contains(SBB)) { | |||
| 7826 | if (Exit) // Multiple exit successors. | |||
| 7827 | return getCouldNotCompute(); | |||
| 7828 | Exit = SBB; | |||
| 7829 | } | |||
| 7830 | assert(Exit && "Exiting block must have at least one exit")((void)0); | |||
| 7831 | return computeExitLimitFromSingleExitSwitch(L, SI, Exit, | |||
| 7832 | /*ControlsExit=*/IsOnlyExit); | |||
| 7833 | } | |||
| 7834 | ||||
| 7835 | return getCouldNotCompute(); | |||
| 7836 | } | |||
| 7837 | ||||
| 7838 | ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromCond( | |||
| 7839 | const Loop *L, Value *ExitCond, bool ExitIfTrue, | |||
| 7840 | bool ControlsExit, bool AllowPredicates) { | |||
| 7841 | ScalarEvolution::ExitLimitCacheTy Cache(L, ExitIfTrue, AllowPredicates); | |||
| 7842 | return computeExitLimitFromCondCached(Cache, L, ExitCond, ExitIfTrue, | |||
| 7843 | ControlsExit, AllowPredicates); | |||
| 7844 | } | |||
| 7845 | ||||
| 7846 | Optional<ScalarEvolution::ExitLimit> | |||
| 7847 | ScalarEvolution::ExitLimitCache::find(const Loop *L, Value *ExitCond, | |||
| 7848 | bool ExitIfTrue, bool ControlsExit, | |||
| 7849 | bool AllowPredicates) { | |||
| 7850 | (void)this->L; | |||
| 7851 | (void)this->ExitIfTrue; | |||
| 7852 | (void)this->AllowPredicates; | |||
| 7853 | ||||
| 7854 | assert(this->L == L && this->ExitIfTrue == ExitIfTrue &&((void)0) | |||
| 7855 | this->AllowPredicates == AllowPredicates &&((void)0) | |||
| 7856 | "Variance in assumed invariant key components!")((void)0); | |||
| 7857 | auto Itr = TripCountMap.find({ExitCond, ControlsExit}); | |||
| 7858 | if (Itr == TripCountMap.end()) | |||
| 7859 | return None; | |||
| 7860 | return Itr->second; | |||
| 7861 | } | |||
| 7862 | ||||
| 7863 | void ScalarEvolution::ExitLimitCache::insert(const Loop *L, Value *ExitCond, | |||
| 7864 | bool ExitIfTrue, | |||
| 7865 | bool ControlsExit, | |||
| 7866 | bool AllowPredicates, | |||
| 7867 | const ExitLimit &EL) { | |||
| 7868 | assert(this->L == L && this->ExitIfTrue == ExitIfTrue &&((void)0) | |||
| 7869 | this->AllowPredicates == AllowPredicates &&((void)0) | |||
| 7870 | "Variance in assumed invariant key components!")((void)0); | |||
| 7871 | ||||
| 7872 | auto InsertResult = TripCountMap.insert({{ExitCond, ControlsExit}, EL}); | |||
| 7873 | assert(InsertResult.second && "Expected successful insertion!")((void)0); | |||
| 7874 | (void)InsertResult; | |||
| 7875 | (void)ExitIfTrue; | |||
| 7876 | } | |||
| 7877 | ||||
| 7878 | ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromCondCached( | |||
| 7879 | ExitLimitCacheTy &Cache, const Loop *L, Value *ExitCond, bool ExitIfTrue, | |||
| 7880 | bool ControlsExit, bool AllowPredicates) { | |||
| 7881 | ||||
| 7882 | if (auto MaybeEL = | |||
| 7883 | Cache.find(L, ExitCond, ExitIfTrue, ControlsExit, AllowPredicates)) | |||
| 7884 | return *MaybeEL; | |||
| 7885 | ||||
| 7886 | ExitLimit EL = computeExitLimitFromCondImpl(Cache, L, ExitCond, ExitIfTrue, | |||
| 7887 | ControlsExit, AllowPredicates); | |||
| 7888 | Cache.insert(L, ExitCond, ExitIfTrue, ControlsExit, AllowPredicates, EL); | |||
| 7889 | return EL; | |||
| 7890 | } | |||
| 7891 | ||||
| 7892 | ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromCondImpl( | |||
| 7893 | ExitLimitCacheTy &Cache, const Loop *L, Value *ExitCond, bool ExitIfTrue, | |||
| 7894 | bool ControlsExit, bool AllowPredicates) { | |||
| 7895 | // Handle BinOp conditions (And, Or). | |||
| 7896 | if (auto LimitFromBinOp = computeExitLimitFromCondFromBinOp( | |||
| 7897 | Cache, L, ExitCond, ExitIfTrue, ControlsExit, AllowPredicates)) | |||
| 7898 | return *LimitFromBinOp; | |||
| 7899 | ||||
| 7900 | // With an icmp, it may be feasible to compute an exact backedge-taken count. | |||
| 7901 | // Proceed to the next level to examine the icmp. | |||
| 7902 | if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond)) { | |||
| 7903 | ExitLimit EL = | |||
| 7904 | computeExitLimitFromICmp(L, ExitCondICmp, ExitIfTrue, ControlsExit); | |||
| 7905 | if (EL.hasFullInfo() || !AllowPredicates) | |||
| 7906 | return EL; | |||
| 7907 | ||||
| 7908 | // Try again, but use SCEV predicates this time. | |||
| 7909 | return computeExitLimitFromICmp(L, ExitCondICmp, ExitIfTrue, ControlsExit, | |||
| 7910 | /*AllowPredicates=*/true); | |||
| 7911 | } | |||
| 7912 | ||||
| 7913 | // Check for a constant condition. These are normally stripped out by | |||
| 7914 | // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to | |||
| 7915 | // preserve the CFG and is temporarily leaving constant conditions | |||
| 7916 | // in place. | |||
| 7917 | if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) { | |||
| 7918 | if (ExitIfTrue == !CI->getZExtValue()) | |||
| 7919 | // The backedge is always taken. | |||
| 7920 | return getCouldNotCompute(); | |||
| 7921 | else | |||
| 7922 | // The backedge is never taken. | |||
| 7923 | return getZero(CI->getType()); | |||
| 7924 | } | |||
| 7925 | ||||
| 7926 | // If it's not an integer or pointer comparison then compute it the hard way. | |||
| 7927 | return computeExitCountExhaustively(L, ExitCond, ExitIfTrue); | |||
| 7928 | } | |||
| 7929 | ||||
| 7930 | Optional<ScalarEvolution::ExitLimit> | |||
| 7931 | ScalarEvolution::computeExitLimitFromCondFromBinOp( | |||
| 7932 | ExitLimitCacheTy &Cache, const Loop *L, Value *ExitCond, bool ExitIfTrue, | |||
| 7933 | bool ControlsExit, bool AllowPredicates) { | |||
| 7934 | // Check if the controlling expression for this loop is an And or Or. | |||
| 7935 | Value *Op0, *Op1; | |||
| 7936 | bool IsAnd = false; | |||
| 7937 | if (match(ExitCond, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) | |||
| 7938 | IsAnd = true; | |||
| 7939 | else if (match(ExitCond, m_LogicalOr(m_Value(Op0), m_Value(Op1)))) | |||
| 7940 | IsAnd = false; | |||
| 7941 | else | |||
| 7942 | return None; | |||
| 7943 | ||||
| 7944 | // EitherMayExit is true in these two cases: | |||
| 7945 | // br (and Op0 Op1), loop, exit | |||
| 7946 | // br (or Op0 Op1), exit, loop | |||
| 7947 | bool EitherMayExit = IsAnd ^ ExitIfTrue; | |||
| 7948 | ExitLimit EL0 = computeExitLimitFromCondCached(Cache, L, Op0, ExitIfTrue, | |||
| 7949 | ControlsExit && !EitherMayExit, | |||
| 7950 | AllowPredicates); | |||
| 7951 | ExitLimit EL1 = computeExitLimitFromCondCached(Cache, L, Op1, ExitIfTrue, | |||
| 7952 | ControlsExit && !EitherMayExit, | |||
| 7953 | AllowPredicates); | |||
| 7954 | ||||
| 7955 | // Be robust against unsimplified IR for the form "op i1 X, NeutralElement" | |||
| 7956 | const Constant *NeutralElement = ConstantInt::get(ExitCond->getType(), IsAnd); | |||
| 7957 | if (isa<ConstantInt>(Op1)) | |||
| 7958 | return Op1 == NeutralElement ? EL0 : EL1; | |||
| 7959 | if (isa<ConstantInt>(Op0)) | |||
| 7960 | return Op0 == NeutralElement ? EL1 : EL0; | |||
| 7961 | ||||
| 7962 | const SCEV *BECount = getCouldNotCompute(); | |||
| 7963 | const SCEV *MaxBECount = getCouldNotCompute(); | |||
| 7964 | if (EitherMayExit) { | |||
| 7965 | // Both conditions must be same for the loop to continue executing. | |||
| 7966 | // Choose the less conservative count. | |||
| 7967 | // If ExitCond is a short-circuit form (select), using | |||
| 7968 | // umin(EL0.ExactNotTaken, EL1.ExactNotTaken) is unsafe in general. | |||
| 7969 | // To see the detailed examples, please see | |||
| 7970 | // test/Analysis/ScalarEvolution/exit-count-select.ll | |||
| 7971 | bool PoisonSafe = isa<BinaryOperator>(ExitCond); | |||
| 7972 | if (!PoisonSafe) | |||
| 7973 | // Even if ExitCond is select, we can safely derive BECount using both | |||
| 7974 | // EL0 and EL1 in these cases: | |||
| 7975 | // (1) EL0.ExactNotTaken is non-zero | |||
| 7976 | // (2) EL1.ExactNotTaken is non-poison | |||
| 7977 | // (3) EL0.ExactNotTaken is zero (BECount should be simply zero and | |||
| 7978 | // it cannot be umin(0, ..)) | |||
| 7979 | // The PoisonSafe assignment below is simplified and the assertion after | |||
| 7980 | // BECount calculation fully guarantees the condition (3). | |||
| 7981 | PoisonSafe = isa<SCEVConstant>(EL0.ExactNotTaken) || | |||
| 7982 | isa<SCEVConstant>(EL1.ExactNotTaken); | |||
| 7983 | if (EL0.ExactNotTaken != getCouldNotCompute() && | |||
| 7984 | EL1.ExactNotTaken != getCouldNotCompute() && PoisonSafe) { | |||
| 7985 | BECount = | |||
| 7986 | getUMinFromMismatchedTypes(EL0.ExactNotTaken, EL1.ExactNotTaken); | |||
| 7987 | ||||
| 7988 | // If EL0.ExactNotTaken was zero and ExitCond was a short-circuit form, | |||
| 7989 | // it should have been simplified to zero (see the condition (3) above) | |||
| 7990 | assert(!isa<BinaryOperator>(ExitCond) || !EL0.ExactNotTaken->isZero() ||((void)0) | |||
| 7991 | BECount->isZero())((void)0); | |||
| 7992 | } | |||
| 7993 | if (EL0.MaxNotTaken == getCouldNotCompute()) | |||
| 7994 | MaxBECount = EL1.MaxNotTaken; | |||
| 7995 | else if (EL1.MaxNotTaken == getCouldNotCompute()) | |||
| 7996 | MaxBECount = EL0.MaxNotTaken; | |||
| 7997 | else | |||
| 7998 | MaxBECount = getUMinFromMismatchedTypes(EL0.MaxNotTaken, EL1.MaxNotTaken); | |||
| 7999 | } else { | |||
| 8000 | // Both conditions must be same at the same time for the loop to exit. | |||
| 8001 | // For now, be conservative. | |||
| 8002 | if (EL0.ExactNotTaken == EL1.ExactNotTaken) | |||
| 8003 | BECount = EL0.ExactNotTaken; | |||
| 8004 | } | |||
| 8005 | ||||
| 8006 | // There are cases (e.g. PR26207) where computeExitLimitFromCond is able | |||
| 8007 | // to be more aggressive when computing BECount than when computing | |||
| 8008 | // MaxBECount. In these cases it is possible for EL0.ExactNotTaken and | |||
| 8009 | // EL1.ExactNotTaken to match, but for EL0.MaxNotTaken and EL1.MaxNotTaken | |||
| 8010 | // to not. | |||
| 8011 | if (isa<SCEVCouldNotCompute>(MaxBECount) && | |||
| 8012 | !isa<SCEVCouldNotCompute>(BECount)) | |||
| 8013 | MaxBECount = getConstant(getUnsignedRangeMax(BECount)); | |||
| 8014 | ||||
| 8015 | return ExitLimit(BECount, MaxBECount, false, | |||
| 8016 | { &EL0.Predicates, &EL1.Predicates }); | |||
| 8017 | } | |||
| 8018 | ||||
| 8019 | ScalarEvolution::ExitLimit | |||
| 8020 | ScalarEvolution::computeExitLimitFromICmp(const Loop *L, | |||
| 8021 | ICmpInst *ExitCond, | |||
| 8022 | bool ExitIfTrue, | |||
| 8023 | bool ControlsExit, | |||
| 8024 | bool AllowPredicates) { | |||
| 8025 | // If the condition was exit on true, convert the condition to exit on false | |||
| 8026 | ICmpInst::Predicate Pred; | |||
| 8027 | if (!ExitIfTrue) | |||
| 8028 | Pred = ExitCond->getPredicate(); | |||
| 8029 | else | |||
| 8030 | Pred = ExitCond->getInversePredicate(); | |||
| 8031 | const ICmpInst::Predicate OriginalPred = Pred; | |||
| 8032 | ||||
| 8033 | // Handle common loops like: for (X = "string"; *X; ++X) | |||
| 8034 | if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0))) | |||
| 8035 | if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) { | |||
| 8036 | ExitLimit ItCnt = | |||
| 8037 | computeLoadConstantCompareExitLimit(LI, RHS, L, Pred); | |||
| 8038 | if (ItCnt.hasAnyInfo()) | |||
| 8039 | return ItCnt; | |||
| 8040 | } | |||
| 8041 | ||||
| 8042 | const SCEV *LHS = getSCEV(ExitCond->getOperand(0)); | |||
| 8043 | const SCEV *RHS = getSCEV(ExitCond->getOperand(1)); | |||
| 8044 | ||||
| 8045 | // Try to evaluate any dependencies out of the loop. | |||
| 8046 | LHS = getSCEVAtScope(LHS, L); | |||
| 8047 | RHS = getSCEVAtScope(RHS, L); | |||
| 8048 | ||||
| 8049 | // At this point, we would like to compute how many iterations of the | |||
| 8050 | // loop the predicate will return true for these inputs. | |||
| 8051 | if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) { | |||
| 8052 | // If there is a loop-invariant, force it into the RHS. | |||
| 8053 | std::swap(LHS, RHS); | |||
| 8054 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 8055 | } | |||
| 8056 | ||||
| 8057 | // Simplify the operands before analyzing them. | |||
| 8058 | (void)SimplifyICmpOperands(Pred, LHS, RHS); | |||
| 8059 | ||||
| 8060 | // If we have a comparison of a chrec against a constant, try to use value | |||
| 8061 | // ranges to answer this query. | |||
| 8062 | if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) | |||
| 8063 | if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS)) | |||
| 8064 | if (AddRec->getLoop() == L) { | |||
| 8065 | // Form the constant range. | |||
| 8066 | ConstantRange CompRange = | |||
| 8067 | ConstantRange::makeExactICmpRegion(Pred, RHSC->getAPInt()); | |||
| 8068 | ||||
| 8069 | const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this); | |||
| 8070 | if (!isa<SCEVCouldNotCompute>(Ret)) return Ret; | |||
| 8071 | } | |||
| 8072 | ||||
| 8073 | switch (Pred) { | |||
| 8074 | case ICmpInst::ICMP_NE: { // while (X != Y) | |||
| 8075 | // Convert to: while (X-Y != 0) | |||
| 8076 | if (LHS->getType()->isPointerTy()) { | |||
| 8077 | LHS = getLosslessPtrToIntExpr(LHS); | |||
| 8078 | if (isa<SCEVCouldNotCompute>(LHS)) | |||
| 8079 | return LHS; | |||
| 8080 | } | |||
| 8081 | if (RHS->getType()->isPointerTy()) { | |||
| 8082 | RHS = getLosslessPtrToIntExpr(RHS); | |||
| 8083 | if (isa<SCEVCouldNotCompute>(RHS)) | |||
| 8084 | return RHS; | |||
| 8085 | } | |||
| 8086 | ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit, | |||
| 8087 | AllowPredicates); | |||
| 8088 | if (EL.hasAnyInfo()) return EL; | |||
| 8089 | break; | |||
| 8090 | } | |||
| 8091 | case ICmpInst::ICMP_EQ: { // while (X == Y) | |||
| 8092 | // Convert to: while (X-Y == 0) | |||
| 8093 | if (LHS->getType()->isPointerTy()) { | |||
| 8094 | LHS = getLosslessPtrToIntExpr(LHS); | |||
| 8095 | if (isa<SCEVCouldNotCompute>(LHS)) | |||
| 8096 | return LHS; | |||
| 8097 | } | |||
| 8098 | if (RHS->getType()->isPointerTy()) { | |||
| 8099 | RHS = getLosslessPtrToIntExpr(RHS); | |||
| 8100 | if (isa<SCEVCouldNotCompute>(RHS)) | |||
| 8101 | return RHS; | |||
| 8102 | } | |||
| 8103 | ExitLimit EL = howFarToNonZero(getMinusSCEV(LHS, RHS), L); | |||
| 8104 | if (EL.hasAnyInfo()) return EL; | |||
| 8105 | break; | |||
| 8106 | } | |||
| 8107 | case ICmpInst::ICMP_SLT: | |||
| 8108 | case ICmpInst::ICMP_ULT: { // while (X < Y) | |||
| 8109 | bool IsSigned = Pred == ICmpInst::ICMP_SLT; | |||
| 8110 | ExitLimit EL = howManyLessThans(LHS, RHS, L, IsSigned, ControlsExit, | |||
| 8111 | AllowPredicates); | |||
| 8112 | if (EL.hasAnyInfo()) return EL; | |||
| 8113 | break; | |||
| 8114 | } | |||
| 8115 | case ICmpInst::ICMP_SGT: | |||
| 8116 | case ICmpInst::ICMP_UGT: { // while (X > Y) | |||
| 8117 | bool IsSigned = Pred == ICmpInst::ICMP_SGT; | |||
| 8118 | ExitLimit EL = | |||
| 8119 | howManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit, | |||
| 8120 | AllowPredicates); | |||
| 8121 | if (EL.hasAnyInfo()) return EL; | |||
| 8122 | break; | |||
| 8123 | } | |||
| 8124 | default: | |||
| 8125 | break; | |||
| 8126 | } | |||
| 8127 | ||||
| 8128 | auto *ExhaustiveCount = | |||
| 8129 | computeExitCountExhaustively(L, ExitCond, ExitIfTrue); | |||
| 8130 | ||||
| 8131 | if (!isa<SCEVCouldNotCompute>(ExhaustiveCount)) | |||
| 8132 | return ExhaustiveCount; | |||
| 8133 | ||||
| 8134 | return computeShiftCompareExitLimit(ExitCond->getOperand(0), | |||
| 8135 | ExitCond->getOperand(1), L, OriginalPred); | |||
| 8136 | } | |||
| 8137 | ||||
| 8138 | ScalarEvolution::ExitLimit | |||
| 8139 | ScalarEvolution::computeExitLimitFromSingleExitSwitch(const Loop *L, | |||
| 8140 | SwitchInst *Switch, | |||
| 8141 | BasicBlock *ExitingBlock, | |||
| 8142 | bool ControlsExit) { | |||
| 8143 | assert(!L->contains(ExitingBlock) && "Not an exiting block!")((void)0); | |||
| 8144 | ||||
| 8145 | // Give up if the exit is the default dest of a switch. | |||
| 8146 | if (Switch->getDefaultDest() == ExitingBlock) | |||
| 8147 | return getCouldNotCompute(); | |||
| 8148 | ||||
| 8149 | assert(L->contains(Switch->getDefaultDest()) &&((void)0) | |||
| 8150 | "Default case must not exit the loop!")((void)0); | |||
| 8151 | const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L); | |||
| 8152 | const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock)); | |||
| 8153 | ||||
| 8154 | // while (X != Y) --> while (X-Y != 0) | |||
| 8155 | ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit); | |||
| 8156 | if (EL.hasAnyInfo()) | |||
| 8157 | return EL; | |||
| 8158 | ||||
| 8159 | return getCouldNotCompute(); | |||
| 8160 | } | |||
| 8161 | ||||
| 8162 | static ConstantInt * | |||
| 8163 | EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C, | |||
| 8164 | ScalarEvolution &SE) { | |||
| 8165 | const SCEV *InVal = SE.getConstant(C); | |||
| 8166 | const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE); | |||
| 8167 | assert(isa<SCEVConstant>(Val) &&((void)0) | |||
| 8168 | "Evaluation of SCEV at constant didn't fold correctly?")((void)0); | |||
| 8169 | return cast<SCEVConstant>(Val)->getValue(); | |||
| 8170 | } | |||
| 8171 | ||||
| 8172 | /// Given an exit condition of 'icmp op load X, cst', try to see if we can | |||
| 8173 | /// compute the backedge execution count. | |||
| 8174 | ScalarEvolution::ExitLimit | |||
| 8175 | ScalarEvolution::computeLoadConstantCompareExitLimit( | |||
| 8176 | LoadInst *LI, | |||
| 8177 | Constant *RHS, | |||
| 8178 | const Loop *L, | |||
| 8179 | ICmpInst::Predicate predicate) { | |||
| 8180 | if (LI->isVolatile()) return getCouldNotCompute(); | |||
| 8181 | ||||
| 8182 | // Check to see if the loaded pointer is a getelementptr of a global. | |||
| 8183 | // TODO: Use SCEV instead of manually grubbing with GEPs. | |||
| 8184 | GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)); | |||
| 8185 | if (!GEP) return getCouldNotCompute(); | |||
| 8186 | ||||
| 8187 | // Make sure that it is really a constant global we are gepping, with an | |||
| 8188 | // initializer, and make sure the first IDX is really 0. | |||
| 8189 | GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)); | |||
| 8190 | if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || | |||
| 8191 | GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) || | |||
| 8192 | !cast<Constant>(GEP->getOperand(1))->isNullValue()) | |||
| 8193 | return getCouldNotCompute(); | |||
| 8194 | ||||
| 8195 | // Okay, we allow one non-constant index into the GEP instruction. | |||
| 8196 | Value *VarIdx = nullptr; | |||
| 8197 | std::vector<Constant*> Indexes; | |||
| 8198 | unsigned VarIdxNum = 0; | |||
| 8199 | for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) | |||
| 8200 | if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) { | |||
| 8201 | Indexes.push_back(CI); | |||
| 8202 | } else if (!isa<ConstantInt>(GEP->getOperand(i))) { | |||
| 8203 | if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's. | |||
| 8204 | VarIdx = GEP->getOperand(i); | |||
| 8205 | VarIdxNum = i-2; | |||
| 8206 | Indexes.push_back(nullptr); | |||
| 8207 | } | |||
| 8208 | ||||
| 8209 | // Loop-invariant loads may be a byproduct of loop optimization. Skip them. | |||
| 8210 | if (!VarIdx) | |||
| 8211 | return getCouldNotCompute(); | |||
| 8212 | ||||
| 8213 | // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant. | |||
| 8214 | // Check to see if X is a loop variant variable value now. | |||
| 8215 | const SCEV *Idx = getSCEV(VarIdx); | |||
| 8216 | Idx = getSCEVAtScope(Idx, L); | |||
| 8217 | ||||
| 8218 | // We can only recognize very limited forms of loop index expressions, in | |||
| 8219 | // particular, only affine AddRec's like {C1,+,C2}<L>. | |||
| 8220 | const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx); | |||
| 8221 | if (!IdxExpr || IdxExpr->getLoop() != L || !IdxExpr->isAffine() || | |||
| 8222 | isLoopInvariant(IdxExpr, L) || | |||
| 8223 | !isa<SCEVConstant>(IdxExpr->getOperand(0)) || | |||
| 8224 | !isa<SCEVConstant>(IdxExpr->getOperand(1))) | |||
| 8225 | return getCouldNotCompute(); | |||
| 8226 | ||||
| 8227 | unsigned MaxSteps = MaxBruteForceIterations; | |||
| 8228 | for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) { | |||
| 8229 | ConstantInt *ItCst = ConstantInt::get( | |||
| 8230 | cast<IntegerType>(IdxExpr->getType()), IterationNum); | |||
| 8231 | ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this); | |||
| 8232 | ||||
| 8233 | // Form the GEP offset. | |||
| 8234 | Indexes[VarIdxNum] = Val; | |||
| 8235 | ||||
| 8236 | Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(), | |||
| 8237 | Indexes); | |||
| 8238 | if (!Result) break; // Cannot compute! | |||
| 8239 | ||||
| 8240 | // Evaluate the condition for this iteration. | |||
| 8241 | Result = ConstantExpr::getICmp(predicate, Result, RHS); | |||
| 8242 | if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure | |||
| 8243 | if (cast<ConstantInt>(Result)->getValue().isMinValue()) { | |||
| 8244 | ++NumArrayLenItCounts; | |||
| 8245 | return getConstant(ItCst); // Found terminating iteration! | |||
| 8246 | } | |||
| 8247 | } | |||
| 8248 | return getCouldNotCompute(); | |||
| 8249 | } | |||
| 8250 | ||||
| 8251 | ScalarEvolution::ExitLimit ScalarEvolution::computeShiftCompareExitLimit( | |||
| 8252 | Value *LHS, Value *RHSV, const Loop *L, ICmpInst::Predicate Pred) { | |||
| 8253 | ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV); | |||
| 8254 | if (!RHS) | |||
| 8255 | return getCouldNotCompute(); | |||
| 8256 | ||||
| 8257 | const BasicBlock *Latch = L->getLoopLatch(); | |||
| 8258 | if (!Latch) | |||
| 8259 | return getCouldNotCompute(); | |||
| 8260 | ||||
| 8261 | const BasicBlock *Predecessor = L->getLoopPredecessor(); | |||
| 8262 | if (!Predecessor) | |||
| 8263 | return getCouldNotCompute(); | |||
| 8264 | ||||
| 8265 | // Return true if V is of the form "LHS `shift_op` <positive constant>". | |||
| 8266 | // Return LHS in OutLHS and shift_opt in OutOpCode. | |||
| 8267 | auto MatchPositiveShift = | |||
| 8268 | [](Value *V, Value *&OutLHS, Instruction::BinaryOps &OutOpCode) { | |||
| 8269 | ||||
| 8270 | using namespace PatternMatch; | |||
| 8271 | ||||
| 8272 | ConstantInt *ShiftAmt; | |||
| 8273 | if (match(V, m_LShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt)))) | |||
| 8274 | OutOpCode = Instruction::LShr; | |||
| 8275 | else if (match(V, m_AShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt)))) | |||
| 8276 | OutOpCode = Instruction::AShr; | |||
| 8277 | else if (match(V, m_Shl(m_Value(OutLHS), m_ConstantInt(ShiftAmt)))) | |||
| 8278 | OutOpCode = Instruction::Shl; | |||
| 8279 | else | |||
| 8280 | return false; | |||
| 8281 | ||||
| 8282 | return ShiftAmt->getValue().isStrictlyPositive(); | |||
| 8283 | }; | |||
| 8284 | ||||
| 8285 | // Recognize a "shift recurrence" either of the form %iv or of %iv.shifted in | |||
| 8286 | // | |||
| 8287 | // loop: | |||
| 8288 | // %iv = phi i32 [ %iv.shifted, %loop ], [ %val, %preheader ] | |||
| 8289 | // %iv.shifted = lshr i32 %iv, <positive constant> | |||
| 8290 | // | |||
| 8291 | // Return true on a successful match. Return the corresponding PHI node (%iv | |||
| 8292 | // above) in PNOut and the opcode of the shift operation in OpCodeOut. | |||
| 8293 | auto MatchShiftRecurrence = | |||
| 8294 | [&](Value *V, PHINode *&PNOut, Instruction::BinaryOps &OpCodeOut) { | |||
| 8295 | Optional<Instruction::BinaryOps> PostShiftOpCode; | |||
| 8296 | ||||
| 8297 | { | |||
| 8298 | Instruction::BinaryOps OpC; | |||
| 8299 | Value *V; | |||
| 8300 | ||||
| 8301 | // If we encounter a shift instruction, "peel off" the shift operation, | |||
| 8302 | // and remember that we did so. Later when we inspect %iv's backedge | |||
| 8303 | // value, we will make sure that the backedge value uses the same | |||
| 8304 | // operation. | |||
| 8305 | // | |||
| 8306 | // Note: the peeled shift operation does not have to be the same | |||
| 8307 | // instruction as the one feeding into the PHI's backedge value. We only | |||
| 8308 | // really care about it being the same *kind* of shift instruction -- | |||
| 8309 | // that's all that is required for our later inferences to hold. | |||
| 8310 | if (MatchPositiveShift(LHS, V, OpC)) { | |||
| 8311 | PostShiftOpCode = OpC; | |||
| 8312 | LHS = V; | |||
| 8313 | } | |||
| 8314 | } | |||
| 8315 | ||||
| 8316 | PNOut = dyn_cast<PHINode>(LHS); | |||
| 8317 | if (!PNOut || PNOut->getParent() != L->getHeader()) | |||
| 8318 | return false; | |||
| 8319 | ||||
| 8320 | Value *BEValue = PNOut->getIncomingValueForBlock(Latch); | |||
| 8321 | Value *OpLHS; | |||
| 8322 | ||||
| 8323 | return | |||
| 8324 | // The backedge value for the PHI node must be a shift by a positive | |||
| 8325 | // amount | |||
| 8326 | MatchPositiveShift(BEValue, OpLHS, OpCodeOut) && | |||
| 8327 | ||||
| 8328 | // of the PHI node itself | |||
| 8329 | OpLHS == PNOut && | |||
| 8330 | ||||
| 8331 | // and the kind of shift should be match the kind of shift we peeled | |||
| 8332 | // off, if any. | |||
| 8333 | (!PostShiftOpCode.hasValue() || *PostShiftOpCode == OpCodeOut); | |||
| 8334 | }; | |||
| 8335 | ||||
| 8336 | PHINode *PN; | |||
| 8337 | Instruction::BinaryOps OpCode; | |||
| 8338 | if (!MatchShiftRecurrence(LHS, PN, OpCode)) | |||
| 8339 | return getCouldNotCompute(); | |||
| 8340 | ||||
| 8341 | const DataLayout &DL = getDataLayout(); | |||
| 8342 | ||||
| 8343 | // The key rationale for this optimization is that for some kinds of shift | |||
| 8344 | // recurrences, the value of the recurrence "stabilizes" to either 0 or -1 | |||
| 8345 | // within a finite number of iterations. If the condition guarding the | |||
| 8346 | // backedge (in the sense that the backedge is taken if the condition is true) | |||
| 8347 | // is false for the value the shift recurrence stabilizes to, then we know | |||
| 8348 | // that the backedge is taken only a finite number of times. | |||
| 8349 | ||||
| 8350 | ConstantInt *StableValue = nullptr; | |||
| 8351 | switch (OpCode) { | |||
| 8352 | default: | |||
| 8353 | llvm_unreachable("Impossible case!")__builtin_unreachable(); | |||
| 8354 | ||||
| 8355 | case Instruction::AShr: { | |||
| 8356 | // {K,ashr,<positive-constant>} stabilizes to signum(K) in at most | |||
| 8357 | // bitwidth(K) iterations. | |||
| 8358 | Value *FirstValue = PN->getIncomingValueForBlock(Predecessor); | |||
| 8359 | KnownBits Known = computeKnownBits(FirstValue, DL, 0, &AC, | |||
| 8360 | Predecessor->getTerminator(), &DT); | |||
| 8361 | auto *Ty = cast<IntegerType>(RHS->getType()); | |||
| 8362 | if (Known.isNonNegative()) | |||
| 8363 | StableValue = ConstantInt::get(Ty, 0); | |||
| 8364 | else if (Known.isNegative()) | |||
| 8365 | StableValue = ConstantInt::get(Ty, -1, true); | |||
| 8366 | else | |||
| 8367 | return getCouldNotCompute(); | |||
| 8368 | ||||
| 8369 | break; | |||
| 8370 | } | |||
| 8371 | case Instruction::LShr: | |||
| 8372 | case Instruction::Shl: | |||
| 8373 | // Both {K,lshr,<positive-constant>} and {K,shl,<positive-constant>} | |||
| 8374 | // stabilize to 0 in at most bitwidth(K) iterations. | |||
| 8375 | StableValue = ConstantInt::get(cast<IntegerType>(RHS->getType()), 0); | |||
| 8376 | break; | |||
| 8377 | } | |||
| 8378 | ||||
| 8379 | auto *Result = | |||
| 8380 | ConstantFoldCompareInstOperands(Pred, StableValue, RHS, DL, &TLI); | |||
| 8381 | assert(Result->getType()->isIntegerTy(1) &&((void)0) | |||
| 8382 | "Otherwise cannot be an operand to a branch instruction")((void)0); | |||
| 8383 | ||||
| 8384 | if (Result->isZeroValue()) { | |||
| 8385 | unsigned BitWidth = getTypeSizeInBits(RHS->getType()); | |||
| 8386 | const SCEV *UpperBound = | |||
| 8387 | getConstant(getEffectiveSCEVType(RHS->getType()), BitWidth); | |||
| 8388 | return ExitLimit(getCouldNotCompute(), UpperBound, false); | |||
| 8389 | } | |||
| 8390 | ||||
| 8391 | return getCouldNotCompute(); | |||
| 8392 | } | |||
| 8393 | ||||
| 8394 | /// Return true if we can constant fold an instruction of the specified type, | |||
| 8395 | /// assuming that all operands were constants. | |||
| 8396 | static bool CanConstantFold(const Instruction *I) { | |||
| 8397 | if (isa<BinaryOperator>(I) || isa<CmpInst>(I) || | |||
| 8398 | isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) || | |||
| 8399 | isa<LoadInst>(I) || isa<ExtractValueInst>(I)) | |||
| 8400 | return true; | |||
| 8401 | ||||
| 8402 | if (const CallInst *CI = dyn_cast<CallInst>(I)) | |||
| 8403 | if (const Function *F = CI->getCalledFunction()) | |||
| 8404 | return canConstantFoldCallTo(CI, F); | |||
| 8405 | return false; | |||
| 8406 | } | |||
| 8407 | ||||
| 8408 | /// Determine whether this instruction can constant evolve within this loop | |||
| 8409 | /// assuming its operands can all constant evolve. | |||
| 8410 | static bool canConstantEvolve(Instruction *I, const Loop *L) { | |||
| 8411 | // An instruction outside of the loop can't be derived from a loop PHI. | |||
| 8412 | if (!L->contains(I)) return false; | |||
| 8413 | ||||
| 8414 | if (isa<PHINode>(I)) { | |||
| 8415 | // We don't currently keep track of the control flow needed to evaluate | |||
| 8416 | // PHIs, so we cannot handle PHIs inside of loops. | |||
| 8417 | return L->getHeader() == I->getParent(); | |||
| 8418 | } | |||
| 8419 | ||||
| 8420 | // If we won't be able to constant fold this expression even if the operands | |||
| 8421 | // are constants, bail early. | |||
| 8422 | return CanConstantFold(I); | |||
| 8423 | } | |||
| 8424 | ||||
| 8425 | /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by | |||
| 8426 | /// recursing through each instruction operand until reaching a loop header phi. | |||
| 8427 | static PHINode * | |||
| 8428 | getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L, | |||
| 8429 | DenseMap<Instruction *, PHINode *> &PHIMap, | |||
| 8430 | unsigned Depth) { | |||
| 8431 | if (Depth > MaxConstantEvolvingDepth) | |||
| 8432 | return nullptr; | |||
| 8433 | ||||
| 8434 | // Otherwise, we can evaluate this instruction if all of its operands are | |||
| 8435 | // constant or derived from a PHI node themselves. | |||
| 8436 | PHINode *PHI = nullptr; | |||
| 8437 | for (Value *Op : UseInst->operands()) { | |||
| 8438 | if (isa<Constant>(Op)) continue; | |||
| 8439 | ||||
| 8440 | Instruction *OpInst = dyn_cast<Instruction>(Op); | |||
| 8441 | if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr; | |||
| 8442 | ||||
| 8443 | PHINode *P = dyn_cast<PHINode>(OpInst); | |||
| 8444 | if (!P) | |||
| 8445 | // If this operand is already visited, reuse the prior result. | |||
| 8446 | // We may have P != PHI if this is the deepest point at which the | |||
| 8447 | // inconsistent paths meet. | |||
| 8448 | P = PHIMap.lookup(OpInst); | |||
| 8449 | if (!P) { | |||
| 8450 | // Recurse and memoize the results, whether a phi is found or not. | |||
| 8451 | // This recursive call invalidates pointers into PHIMap. | |||
| 8452 | P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap, Depth + 1); | |||
| 8453 | PHIMap[OpInst] = P; | |||
| 8454 | } | |||
| 8455 | if (!P) | |||
| 8456 | return nullptr; // Not evolving from PHI | |||
| 8457 | if (PHI && PHI != P) | |||
| 8458 | return nullptr; // Evolving from multiple different PHIs. | |||
| 8459 | PHI = P; | |||
| 8460 | } | |||
| 8461 | // This is a expression evolving from a constant PHI! | |||
| 8462 | return PHI; | |||
| 8463 | } | |||
| 8464 | ||||
| 8465 | /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node | |||
| 8466 | /// in the loop that V is derived from. We allow arbitrary operations along the | |||
| 8467 | /// way, but the operands of an operation must either be constants or a value | |||
| 8468 | /// derived from a constant PHI. If this expression does not fit with these | |||
| 8469 | /// constraints, return null. | |||
| 8470 | static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) { | |||
| 8471 | Instruction *I = dyn_cast<Instruction>(V); | |||
| 8472 | if (!I || !canConstantEvolve(I, L)) return nullptr; | |||
| 8473 | ||||
| 8474 | if (PHINode *PN = dyn_cast<PHINode>(I)) | |||
| 8475 | return PN; | |||
| 8476 | ||||
| 8477 | // Record non-constant instructions contained by the loop. | |||
| 8478 | DenseMap<Instruction *, PHINode *> PHIMap; | |||
| 8479 | return getConstantEvolvingPHIOperands(I, L, PHIMap, 0); | |||
| 8480 | } | |||
| 8481 | ||||
| 8482 | /// EvaluateExpression - Given an expression that passes the | |||
| 8483 | /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node | |||
| 8484 | /// in the loop has the value PHIVal. If we can't fold this expression for some | |||
| 8485 | /// reason, return null. | |||
| 8486 | static Constant *EvaluateExpression(Value *V, const Loop *L, | |||
| 8487 | DenseMap<Instruction *, Constant *> &Vals, | |||
| 8488 | const DataLayout &DL, | |||
| 8489 | const TargetLibraryInfo *TLI) { | |||
| 8490 | // Convenient constant check, but redundant for recursive calls. | |||
| 8491 | if (Constant *C = dyn_cast<Constant>(V)) return C; | |||
| 8492 | Instruction *I = dyn_cast<Instruction>(V); | |||
| 8493 | if (!I) return nullptr; | |||
| 8494 | ||||
| 8495 | if (Constant *C = Vals.lookup(I)) return C; | |||
| 8496 | ||||
| 8497 | // An instruction inside the loop depends on a value outside the loop that we | |||
| 8498 | // weren't given a mapping for, or a value such as a call inside the loop. | |||
| 8499 | if (!canConstantEvolve(I, L)) return nullptr; | |||
| 8500 | ||||
| 8501 | // An unmapped PHI can be due to a branch or another loop inside this loop, | |||
| 8502 | // or due to this not being the initial iteration through a loop where we | |||
| 8503 | // couldn't compute the evolution of this particular PHI last time. | |||
| 8504 | if (isa<PHINode>(I)) return nullptr; | |||
| 8505 | ||||
| 8506 | std::vector<Constant*> Operands(I->getNumOperands()); | |||
| 8507 | ||||
| 8508 | for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { | |||
| 8509 | Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i)); | |||
| 8510 | if (!Operand) { | |||
| 8511 | Operands[i] = dyn_cast<Constant>(I->getOperand(i)); | |||
| 8512 | if (!Operands[i]) return nullptr; | |||
| 8513 | continue; | |||
| 8514 | } | |||
| 8515 | Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI); | |||
| 8516 | Vals[Operand] = C; | |||
| 8517 | if (!C) return nullptr; | |||
| 8518 | Operands[i] = C; | |||
| 8519 | } | |||
| 8520 | ||||
| 8521 | if (CmpInst *CI = dyn_cast<CmpInst>(I)) | |||
| 8522 | return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0], | |||
| 8523 | Operands[1], DL, TLI); | |||
| 8524 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) { | |||
| 8525 | if (!LI->isVolatile()) | |||
| 8526 | return ConstantFoldLoadFromConstPtr(Operands[0], LI->getType(), DL); | |||
| 8527 | } | |||
| 8528 | return ConstantFoldInstOperands(I, Operands, DL, TLI); | |||
| 8529 | } | |||
| 8530 | ||||
| 8531 | ||||
| 8532 | // If every incoming value to PN except the one for BB is a specific Constant, | |||
| 8533 | // return that, else return nullptr. | |||
| 8534 | static Constant *getOtherIncomingValue(PHINode *PN, BasicBlock *BB) { | |||
| 8535 | Constant *IncomingVal = nullptr; | |||
| 8536 | ||||
| 8537 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { | |||
| 8538 | if (PN->getIncomingBlock(i) == BB) | |||
| 8539 | continue; | |||
| 8540 | ||||
| 8541 | auto *CurrentVal = dyn_cast<Constant>(PN->getIncomingValue(i)); | |||
| 8542 | if (!CurrentVal) | |||
| 8543 | return nullptr; | |||
| 8544 | ||||
| 8545 | if (IncomingVal != CurrentVal) { | |||
| 8546 | if (IncomingVal) | |||
| 8547 | return nullptr; | |||
| 8548 | IncomingVal = CurrentVal; | |||
| 8549 | } | |||
| 8550 | } | |||
| 8551 | ||||
| 8552 | return IncomingVal; | |||
| 8553 | } | |||
| 8554 | ||||
| 8555 | /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is | |||
| 8556 | /// in the header of its containing loop, we know the loop executes a | |||
| 8557 | /// constant number of times, and the PHI node is just a recurrence | |||
| 8558 | /// involving constants, fold it. | |||
| 8559 | Constant * | |||
| 8560 | ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN, | |||
| 8561 | const APInt &BEs, | |||
| 8562 | const Loop *L) { | |||
| 8563 | auto I = ConstantEvolutionLoopExitValue.find(PN); | |||
| 8564 | if (I != ConstantEvolutionLoopExitValue.end()) | |||
| 8565 | return I->second; | |||
| 8566 | ||||
| 8567 | if (BEs.ugt(MaxBruteForceIterations)) | |||
| 8568 | return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it. | |||
| 8569 | ||||
| 8570 | Constant *&RetVal = ConstantEvolutionLoopExitValue[PN]; | |||
| 8571 | ||||
| 8572 | DenseMap<Instruction *, Constant *> CurrentIterVals; | |||
| 8573 | BasicBlock *Header = L->getHeader(); | |||
| 8574 | assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!")((void)0); | |||
| 8575 | ||||
| 8576 | BasicBlock *Latch = L->getLoopLatch(); | |||
| 8577 | if (!Latch) | |||
| 8578 | return nullptr; | |||
| 8579 | ||||
| 8580 | for (PHINode &PHI : Header->phis()) { | |||
| 8581 | if (auto *StartCST = getOtherIncomingValue(&PHI, Latch)) | |||
| 8582 | CurrentIterVals[&PHI] = StartCST; | |||
| 8583 | } | |||
| 8584 | if (!CurrentIterVals.count(PN)) | |||
| 8585 | return RetVal = nullptr; | |||
| 8586 | ||||
| 8587 | Value *BEValue = PN->getIncomingValueForBlock(Latch); | |||
| 8588 | ||||
| 8589 | // Execute the loop symbolically to determine the exit value. | |||
| 8590 | assert(BEs.getActiveBits() < CHAR_BIT * sizeof(unsigned) &&((void)0) | |||
| 8591 | "BEs is <= MaxBruteForceIterations which is an 'unsigned'!")((void)0); | |||
| 8592 | ||||
| 8593 | unsigned NumIterations = BEs.getZExtValue(); // must be in range | |||
| 8594 | unsigned IterationNum = 0; | |||
| 8595 | const DataLayout &DL = getDataLayout(); | |||
| 8596 | for (; ; ++IterationNum) { | |||
| 8597 | if (IterationNum == NumIterations) | |||
| 8598 | return RetVal = CurrentIterVals[PN]; // Got exit value! | |||
| 8599 | ||||
| 8600 | // Compute the value of the PHIs for the next iteration. | |||
| 8601 | // EvaluateExpression adds non-phi values to the CurrentIterVals map. | |||
| 8602 | DenseMap<Instruction *, Constant *> NextIterVals; | |||
| 8603 | Constant *NextPHI = | |||
| 8604 | EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI); | |||
| 8605 | if (!NextPHI) | |||
| 8606 | return nullptr; // Couldn't evaluate! | |||
| 8607 | NextIterVals[PN] = NextPHI; | |||
| 8608 | ||||
| 8609 | bool StoppedEvolving = NextPHI == CurrentIterVals[PN]; | |||
| 8610 | ||||
| 8611 | // Also evaluate the other PHI nodes. However, we don't get to stop if we | |||
| 8612 | // cease to be able to evaluate one of them or if they stop evolving, | |||
| 8613 | // because that doesn't necessarily prevent us from computing PN. | |||
| 8614 | SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute; | |||
| 8615 | for (const auto &I : CurrentIterVals) { | |||
| 8616 | PHINode *PHI = dyn_cast<PHINode>(I.first); | |||
| 8617 | if (!PHI || PHI == PN || PHI->getParent() != Header) continue; | |||
| 8618 | PHIsToCompute.emplace_back(PHI, I.second); | |||
| 8619 | } | |||
| 8620 | // We use two distinct loops because EvaluateExpression may invalidate any | |||
| 8621 | // iterators into CurrentIterVals. | |||
| 8622 | for (const auto &I : PHIsToCompute) { | |||
| 8623 | PHINode *PHI = I.first; | |||
| 8624 | Constant *&NextPHI = NextIterVals[PHI]; | |||
| 8625 | if (!NextPHI) { // Not already computed. | |||
| 8626 | Value *BEValue = PHI->getIncomingValueForBlock(Latch); | |||
| 8627 | NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI); | |||
| 8628 | } | |||
| 8629 | if (NextPHI != I.second) | |||
| 8630 | StoppedEvolving = false; | |||
| 8631 | } | |||
| 8632 | ||||
| 8633 | // If all entries in CurrentIterVals == NextIterVals then we can stop | |||
| 8634 | // iterating, the loop can't continue to change. | |||
| 8635 | if (StoppedEvolving) | |||
| 8636 | return RetVal = CurrentIterVals[PN]; | |||
| 8637 | ||||
| 8638 | CurrentIterVals.swap(NextIterVals); | |||
| 8639 | } | |||
| 8640 | } | |||
| 8641 | ||||
| 8642 | const SCEV *ScalarEvolution::computeExitCountExhaustively(const Loop *L, | |||
| 8643 | Value *Cond, | |||
| 8644 | bool ExitWhen) { | |||
| 8645 | PHINode *PN = getConstantEvolvingPHI(Cond, L); | |||
| 8646 | if (!PN) return getCouldNotCompute(); | |||
| 8647 | ||||
| 8648 | // If the loop is canonicalized, the PHI will have exactly two entries. | |||
| 8649 | // That's the only form we support here. | |||
| 8650 | if (PN->getNumIncomingValues() != 2) return getCouldNotCompute(); | |||
| 8651 | ||||
| 8652 | DenseMap<Instruction *, Constant *> CurrentIterVals; | |||
| 8653 | BasicBlock *Header = L->getHeader(); | |||
| 8654 | assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!")((void)0); | |||
| 8655 | ||||
| 8656 | BasicBlock *Latch = L->getLoopLatch(); | |||
| 8657 | assert(Latch && "Should follow from NumIncomingValues == 2!")((void)0); | |||
| 8658 | ||||
| 8659 | for (PHINode &PHI : Header->phis()) { | |||
| 8660 | if (auto *StartCST = getOtherIncomingValue(&PHI, Latch)) | |||
| 8661 | CurrentIterVals[&PHI] = StartCST; | |||
| 8662 | } | |||
| 8663 | if (!CurrentIterVals.count(PN)) | |||
| 8664 | return getCouldNotCompute(); | |||
| 8665 | ||||
| 8666 | // Okay, we find a PHI node that defines the trip count of this loop. Execute | |||
| 8667 | // the loop symbolically to determine when the condition gets a value of | |||
| 8668 | // "ExitWhen". | |||
| 8669 | unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis. | |||
| 8670 | const DataLayout &DL = getDataLayout(); | |||
| 8671 | for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){ | |||
| 8672 | auto *CondVal = dyn_cast_or_null<ConstantInt>( | |||
| 8673 | EvaluateExpression(Cond, L, CurrentIterVals, DL, &TLI)); | |||
| 8674 | ||||
| 8675 | // Couldn't symbolically evaluate. | |||
| 8676 | if (!CondVal) return getCouldNotCompute(); | |||
| 8677 | ||||
| 8678 | if (CondVal->getValue() == uint64_t(ExitWhen)) { | |||
| 8679 | ++NumBruteForceTripCountsComputed; | |||
| 8680 | return getConstant(Type::getInt32Ty(getContext()), IterationNum); | |||
| 8681 | } | |||
| 8682 | ||||
| 8683 | // Update all the PHI nodes for the next iteration. | |||
| 8684 | DenseMap<Instruction *, Constant *> NextIterVals; | |||
| 8685 | ||||
| 8686 | // Create a list of which PHIs we need to compute. We want to do this before | |||
| 8687 | // calling EvaluateExpression on them because that may invalidate iterators | |||
| 8688 | // into CurrentIterVals. | |||
| 8689 | SmallVector<PHINode *, 8> PHIsToCompute; | |||
| 8690 | for (const auto &I : CurrentIterVals) { | |||
| 8691 | PHINode *PHI = dyn_cast<PHINode>(I.first); | |||
| 8692 | if (!PHI || PHI->getParent() != Header) continue; | |||
| 8693 | PHIsToCompute.push_back(PHI); | |||
| 8694 | } | |||
| 8695 | for (PHINode *PHI : PHIsToCompute) { | |||
| 8696 | Constant *&NextPHI = NextIterVals[PHI]; | |||
| 8697 | if (NextPHI) continue; // Already computed! | |||
| 8698 | ||||
| 8699 | Value *BEValue = PHI->getIncomingValueForBlock(Latch); | |||
| 8700 | NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI); | |||
| 8701 | } | |||
| 8702 | CurrentIterVals.swap(NextIterVals); | |||
| 8703 | } | |||
| 8704 | ||||
| 8705 | // Too many iterations were needed to evaluate. | |||
| 8706 | return getCouldNotCompute(); | |||
| 8707 | } | |||
| 8708 | ||||
| 8709 | const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) { | |||
| 8710 | SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = | |||
| 8711 | ValuesAtScopes[V]; | |||
| 8712 | // Check to see if we've folded this expression at this loop before. | |||
| 8713 | for (auto &LS : Values) | |||
| 8714 | if (LS.first == L) | |||
| 8715 | return LS.second ? LS.second : V; | |||
| 8716 | ||||
| 8717 | Values.emplace_back(L, nullptr); | |||
| 8718 | ||||
| 8719 | // Otherwise compute it. | |||
| 8720 | const SCEV *C = computeSCEVAtScope(V, L); | |||
| 8721 | for (auto &LS : reverse(ValuesAtScopes[V])) | |||
| 8722 | if (LS.first == L) { | |||
| 8723 | LS.second = C; | |||
| 8724 | break; | |||
| 8725 | } | |||
| 8726 | return C; | |||
| 8727 | } | |||
| 8728 | ||||
| 8729 | /// This builds up a Constant using the ConstantExpr interface. That way, we | |||
| 8730 | /// will return Constants for objects which aren't represented by a | |||
| 8731 | /// SCEVConstant, because SCEVConstant is restricted to ConstantInt. | |||
| 8732 | /// Returns NULL if the SCEV isn't representable as a Constant. | |||
| 8733 | static Constant *BuildConstantFromSCEV(const SCEV *V) { | |||
| 8734 | switch (V->getSCEVType()) { | |||
| 8735 | case scCouldNotCompute: | |||
| 8736 | case scAddRecExpr: | |||
| 8737 | return nullptr; | |||
| 8738 | case scConstant: | |||
| 8739 | return cast<SCEVConstant>(V)->getValue(); | |||
| 8740 | case scUnknown: | |||
| 8741 | return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue()); | |||
| 8742 | case scSignExtend: { | |||
| 8743 | const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V); | |||
| 8744 | if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand())) | |||
| 8745 | return ConstantExpr::getSExt(CastOp, SS->getType()); | |||
| 8746 | return nullptr; | |||
| 8747 | } | |||
| 8748 | case scZeroExtend: { | |||
| 8749 | const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V); | |||
| 8750 | if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand())) | |||
| 8751 | return ConstantExpr::getZExt(CastOp, SZ->getType()); | |||
| 8752 | return nullptr; | |||
| 8753 | } | |||
| 8754 | case scPtrToInt: { | |||
| 8755 | const SCEVPtrToIntExpr *P2I = cast<SCEVPtrToIntExpr>(V); | |||
| 8756 | if (Constant *CastOp = BuildConstantFromSCEV(P2I->getOperand())) | |||
| 8757 | return ConstantExpr::getPtrToInt(CastOp, P2I->getType()); | |||
| 8758 | ||||
| 8759 | return nullptr; | |||
| 8760 | } | |||
| 8761 | case scTruncate: { | |||
| 8762 | const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V); | |||
| 8763 | if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand())) | |||
| 8764 | return ConstantExpr::getTrunc(CastOp, ST->getType()); | |||
| 8765 | return nullptr; | |||
| 8766 | } | |||
| 8767 | case scAddExpr: { | |||
| 8768 | const SCEVAddExpr *SA = cast<SCEVAddExpr>(V); | |||
| 8769 | if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) { | |||
| 8770 | if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) { | |||
| 8771 | unsigned AS = PTy->getAddressSpace(); | |||
| 8772 | Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS); | |||
| 8773 | C = ConstantExpr::getBitCast(C, DestPtrTy); | |||
| 8774 | } | |||
| 8775 | for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) { | |||
| 8776 | Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i)); | |||
| 8777 | if (!C2) | |||
| 8778 | return nullptr; | |||
| 8779 | ||||
| 8780 | // First pointer! | |||
| 8781 | if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) { | |||
| 8782 | unsigned AS = C2->getType()->getPointerAddressSpace(); | |||
| 8783 | std::swap(C, C2); | |||
| 8784 | Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS); | |||
| 8785 | // The offsets have been converted to bytes. We can add bytes to an | |||
| 8786 | // i8* by GEP with the byte count in the first index. | |||
| 8787 | C = ConstantExpr::getBitCast(C, DestPtrTy); | |||
| 8788 | } | |||
| 8789 | ||||
| 8790 | // Don't bother trying to sum two pointers. We probably can't | |||
| 8791 | // statically compute a load that results from it anyway. | |||
| 8792 | if (C2->getType()->isPointerTy()) | |||
| 8793 | return nullptr; | |||
| 8794 | ||||
| 8795 | if (C->getType()->isPointerTy()) { | |||
| 8796 | C = ConstantExpr::getGetElementPtr(Type::getInt8Ty(C->getContext()), | |||
| 8797 | C, C2); | |||
| 8798 | } else { | |||
| 8799 | C = ConstantExpr::getAdd(C, C2); | |||
| 8800 | } | |||
| 8801 | } | |||
| 8802 | return C; | |||
| 8803 | } | |||
| 8804 | return nullptr; | |||
| 8805 | } | |||
| 8806 | case scMulExpr: { | |||
| 8807 | const SCEVMulExpr *SM = cast<SCEVMulExpr>(V); | |||
| 8808 | if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) { | |||
| 8809 | // Don't bother with pointers at all. | |||
| 8810 | if (C->getType()->isPointerTy()) | |||
| 8811 | return nullptr; | |||
| 8812 | for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) { | |||
| 8813 | Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i)); | |||
| 8814 | if (!C2 || C2->getType()->isPointerTy()) | |||
| 8815 | return nullptr; | |||
| 8816 | C = ConstantExpr::getMul(C, C2); | |||
| 8817 | } | |||
| 8818 | return C; | |||
| 8819 | } | |||
| 8820 | return nullptr; | |||
| 8821 | } | |||
| 8822 | case scUDivExpr: { | |||
| 8823 | const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V); | |||
| 8824 | if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS())) | |||
| 8825 | if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS())) | |||
| 8826 | if (LHS->getType() == RHS->getType()) | |||
| 8827 | return ConstantExpr::getUDiv(LHS, RHS); | |||
| 8828 | return nullptr; | |||
| 8829 | } | |||
| 8830 | case scSMaxExpr: | |||
| 8831 | case scUMaxExpr: | |||
| 8832 | case scSMinExpr: | |||
| 8833 | case scUMinExpr: | |||
| 8834 | return nullptr; // TODO: smax, umax, smin, umax. | |||
| 8835 | } | |||
| 8836 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 8837 | } | |||
| 8838 | ||||
| 8839 | const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) { | |||
| 8840 | if (isa<SCEVConstant>(V)) return V; | |||
| 8841 | ||||
| 8842 | // If this instruction is evolved from a constant-evolving PHI, compute the | |||
| 8843 | // exit value from the loop without using SCEVs. | |||
| 8844 | if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) { | |||
| 8845 | if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) { | |||
| 8846 | if (PHINode *PN = dyn_cast<PHINode>(I)) { | |||
| 8847 | const Loop *CurrLoop = this->LI[I->getParent()]; | |||
| 8848 | // Looking for loop exit value. | |||
| 8849 | if (CurrLoop && CurrLoop->getParentLoop() == L && | |||
| 8850 | PN->getParent() == CurrLoop->getHeader()) { | |||
| 8851 | // Okay, there is no closed form solution for the PHI node. Check | |||
| 8852 | // to see if the loop that contains it has a known backedge-taken | |||
| 8853 | // count. If so, we may be able to force computation of the exit | |||
| 8854 | // value. | |||
| 8855 | const SCEV *BackedgeTakenCount = getBackedgeTakenCount(CurrLoop); | |||
| 8856 | // This trivial case can show up in some degenerate cases where | |||
| 8857 | // the incoming IR has not yet been fully simplified. | |||
| 8858 | if (BackedgeTakenCount->isZero()) { | |||
| 8859 | Value *InitValue = nullptr; | |||
| 8860 | bool MultipleInitValues = false; | |||
| 8861 | for (unsigned i = 0; i < PN->getNumIncomingValues(); i++) { | |||
| 8862 | if (!CurrLoop->contains(PN->getIncomingBlock(i))) { | |||
| 8863 | if (!InitValue) | |||
| 8864 | InitValue = PN->getIncomingValue(i); | |||
| 8865 | else if (InitValue != PN->getIncomingValue(i)) { | |||
| 8866 | MultipleInitValues = true; | |||
| 8867 | break; | |||
| 8868 | } | |||
| 8869 | } | |||
| 8870 | } | |||
| 8871 | if (!MultipleInitValues && InitValue) | |||
| 8872 | return getSCEV(InitValue); | |||
| 8873 | } | |||
| 8874 | // Do we have a loop invariant value flowing around the backedge | |||
| 8875 | // for a loop which must execute the backedge? | |||
| 8876 | if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) && | |||
| 8877 | isKnownPositive(BackedgeTakenCount) && | |||
| 8878 | PN->getNumIncomingValues() == 2) { | |||
| 8879 | ||||
| 8880 | unsigned InLoopPred = | |||
| 8881 | CurrLoop->contains(PN->getIncomingBlock(0)) ? 0 : 1; | |||
| 8882 | Value *BackedgeVal = PN->getIncomingValue(InLoopPred); | |||
| 8883 | if (CurrLoop->isLoopInvariant(BackedgeVal)) | |||
| 8884 | return getSCEV(BackedgeVal); | |||
| 8885 | } | |||
| 8886 | if (auto *BTCC = dyn_cast<SCEVConstant>(BackedgeTakenCount)) { | |||
| 8887 | // Okay, we know how many times the containing loop executes. If | |||
| 8888 | // this is a constant evolving PHI node, get the final value at | |||
| 8889 | // the specified iteration number. | |||
| 8890 | Constant *RV = getConstantEvolutionLoopExitValue( | |||
| 8891 | PN, BTCC->getAPInt(), CurrLoop); | |||
| 8892 | if (RV) return getSCEV(RV); | |||
| 8893 | } | |||
| 8894 | } | |||
| 8895 | ||||
| 8896 | // If there is a single-input Phi, evaluate it at our scope. If we can | |||
| 8897 | // prove that this replacement does not break LCSSA form, use new value. | |||
| 8898 | if (PN->getNumOperands() == 1) { | |||
| 8899 | const SCEV *Input = getSCEV(PN->getOperand(0)); | |||
| 8900 | const SCEV *InputAtScope = getSCEVAtScope(Input, L); | |||
| 8901 | // TODO: We can generalize it using LI.replacementPreservesLCSSAForm, | |||
| 8902 | // for the simplest case just support constants. | |||
| 8903 | if (isa<SCEVConstant>(InputAtScope)) return InputAtScope; | |||
| 8904 | } | |||
| 8905 | } | |||
| 8906 | ||||
| 8907 | // Okay, this is an expression that we cannot symbolically evaluate | |||
| 8908 | // into a SCEV. Check to see if it's possible to symbolically evaluate | |||
| 8909 | // the arguments into constants, and if so, try to constant propagate the | |||
| 8910 | // result. This is particularly useful for computing loop exit values. | |||
| 8911 | if (CanConstantFold(I)) { | |||
| 8912 | SmallVector<Constant *, 4> Operands; | |||
| 8913 | bool MadeImprovement = false; | |||
| 8914 | for (Value *Op : I->operands()) { | |||
| 8915 | if (Constant *C = dyn_cast<Constant>(Op)) { | |||
| 8916 | Operands.push_back(C); | |||
| 8917 | continue; | |||
| 8918 | } | |||
| 8919 | ||||
| 8920 | // If any of the operands is non-constant and if they are | |||
| 8921 | // non-integer and non-pointer, don't even try to analyze them | |||
| 8922 | // with scev techniques. | |||
| 8923 | if (!isSCEVable(Op->getType())) | |||
| 8924 | return V; | |||
| 8925 | ||||
| 8926 | const SCEV *OrigV = getSCEV(Op); | |||
| 8927 | const SCEV *OpV = getSCEVAtScope(OrigV, L); | |||
| 8928 | MadeImprovement |= OrigV != OpV; | |||
| 8929 | ||||
| 8930 | Constant *C = BuildConstantFromSCEV(OpV); | |||
| 8931 | if (!C) return V; | |||
| 8932 | if (C->getType() != Op->getType()) | |||
| 8933 | C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, | |||
| 8934 | Op->getType(), | |||
| 8935 | false), | |||
| 8936 | C, Op->getType()); | |||
| 8937 | Operands.push_back(C); | |||
| 8938 | } | |||
| 8939 | ||||
| 8940 | // Check to see if getSCEVAtScope actually made an improvement. | |||
| 8941 | if (MadeImprovement) { | |||
| 8942 | Constant *C = nullptr; | |||
| 8943 | const DataLayout &DL = getDataLayout(); | |||
| 8944 | if (const CmpInst *CI = dyn_cast<CmpInst>(I)) | |||
| 8945 | C = ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0], | |||
| 8946 | Operands[1], DL, &TLI); | |||
| 8947 | else if (const LoadInst *Load = dyn_cast<LoadInst>(I)) { | |||
| 8948 | if (!Load->isVolatile()) | |||
| 8949 | C = ConstantFoldLoadFromConstPtr(Operands[0], Load->getType(), | |||
| 8950 | DL); | |||
| 8951 | } else | |||
| 8952 | C = ConstantFoldInstOperands(I, Operands, DL, &TLI); | |||
| 8953 | if (!C) return V; | |||
| 8954 | return getSCEV(C); | |||
| 8955 | } | |||
| 8956 | } | |||
| 8957 | } | |||
| 8958 | ||||
| 8959 | // This is some other type of SCEVUnknown, just return it. | |||
| 8960 | return V; | |||
| 8961 | } | |||
| 8962 | ||||
| 8963 | if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) { | |||
| 8964 | // Avoid performing the look-up in the common case where the specified | |||
| 8965 | // expression has no loop-variant portions. | |||
| 8966 | for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) { | |||
| 8967 | const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L); | |||
| 8968 | if (OpAtScope != Comm->getOperand(i)) { | |||
| 8969 | // Okay, at least one of these operands is loop variant but might be | |||
| 8970 | // foldable. Build a new instance of the folded commutative expression. | |||
| 8971 | SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(), | |||
| 8972 | Comm->op_begin()+i); | |||
| 8973 | NewOps.push_back(OpAtScope); | |||
| 8974 | ||||
| 8975 | for (++i; i != e; ++i) { | |||
| 8976 | OpAtScope = getSCEVAtScope(Comm->getOperand(i), L); | |||
| 8977 | NewOps.push_back(OpAtScope); | |||
| 8978 | } | |||
| 8979 | if (isa<SCEVAddExpr>(Comm)) | |||
| 8980 | return getAddExpr(NewOps, Comm->getNoWrapFlags()); | |||
| 8981 | if (isa<SCEVMulExpr>(Comm)) | |||
| 8982 | return getMulExpr(NewOps, Comm->getNoWrapFlags()); | |||
| 8983 | if (isa<SCEVMinMaxExpr>(Comm)) | |||
| 8984 | return getMinMaxExpr(Comm->getSCEVType(), NewOps); | |||
| 8985 | llvm_unreachable("Unknown commutative SCEV type!")__builtin_unreachable(); | |||
| 8986 | } | |||
| 8987 | } | |||
| 8988 | // If we got here, all operands are loop invariant. | |||
| 8989 | return Comm; | |||
| 8990 | } | |||
| 8991 | ||||
| 8992 | if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) { | |||
| 8993 | const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L); | |||
| 8994 | const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L); | |||
| 8995 | if (LHS == Div->getLHS() && RHS == Div->getRHS()) | |||
| 8996 | return Div; // must be loop invariant | |||
| 8997 | return getUDivExpr(LHS, RHS); | |||
| 8998 | } | |||
| 8999 | ||||
| 9000 | // If this is a loop recurrence for a loop that does not contain L, then we | |||
| 9001 | // are dealing with the final value computed by the loop. | |||
| 9002 | if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) { | |||
| 9003 | // First, attempt to evaluate each operand. | |||
| 9004 | // Avoid performing the look-up in the common case where the specified | |||
| 9005 | // expression has no loop-variant portions. | |||
| 9006 | for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) { | |||
| 9007 | const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L); | |||
| 9008 | if (OpAtScope == AddRec->getOperand(i)) | |||
| 9009 | continue; | |||
| 9010 | ||||
| 9011 | // Okay, at least one of these operands is loop variant but might be | |||
| 9012 | // foldable. Build a new instance of the folded commutative expression. | |||
| 9013 | SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(), | |||
| 9014 | AddRec->op_begin()+i); | |||
| 9015 | NewOps.push_back(OpAtScope); | |||
| 9016 | for (++i; i != e; ++i) | |||
| 9017 | NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L)); | |||
| 9018 | ||||
| 9019 | const SCEV *FoldedRec = | |||
| 9020 | getAddRecExpr(NewOps, AddRec->getLoop(), | |||
| 9021 | AddRec->getNoWrapFlags(SCEV::FlagNW)); | |||
| 9022 | AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec); | |||
| 9023 | // The addrec may be folded to a nonrecurrence, for example, if the | |||
| 9024 | // induction variable is multiplied by zero after constant folding. Go | |||
| 9025 | // ahead and return the folded value. | |||
| 9026 | if (!AddRec) | |||
| 9027 | return FoldedRec; | |||
| 9028 | break; | |||
| 9029 | } | |||
| 9030 | ||||
| 9031 | // If the scope is outside the addrec's loop, evaluate it by using the | |||
| 9032 | // loop exit value of the addrec. | |||
| 9033 | if (!AddRec->getLoop()->contains(L)) { | |||
| 9034 | // To evaluate this recurrence, we need to know how many times the AddRec | |||
| 9035 | // loop iterates. Compute this now. | |||
| 9036 | const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop()); | |||
| 9037 | if (BackedgeTakenCount == getCouldNotCompute()) return AddRec; | |||
| 9038 | ||||
| 9039 | // Then, evaluate the AddRec. | |||
| 9040 | return AddRec->evaluateAtIteration(BackedgeTakenCount, *this); | |||
| 9041 | } | |||
| 9042 | ||||
| 9043 | return AddRec; | |||
| 9044 | } | |||
| 9045 | ||||
| 9046 | if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) { | |||
| 9047 | const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L); | |||
| 9048 | if (Op == Cast->getOperand()) | |||
| 9049 | return Cast; // must be loop invariant | |||
| 9050 | return getZeroExtendExpr(Op, Cast->getType()); | |||
| 9051 | } | |||
| 9052 | ||||
| 9053 | if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) { | |||
| 9054 | const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L); | |||
| 9055 | if (Op == Cast->getOperand()) | |||
| 9056 | return Cast; // must be loop invariant | |||
| 9057 | return getSignExtendExpr(Op, Cast->getType()); | |||
| 9058 | } | |||
| 9059 | ||||
| 9060 | if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) { | |||
| 9061 | const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L); | |||
| 9062 | if (Op == Cast->getOperand()) | |||
| 9063 | return Cast; // must be loop invariant | |||
| 9064 | return getTruncateExpr(Op, Cast->getType()); | |||
| 9065 | } | |||
| 9066 | ||||
| 9067 | if (const SCEVPtrToIntExpr *Cast = dyn_cast<SCEVPtrToIntExpr>(V)) { | |||
| 9068 | const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L); | |||
| 9069 | if (Op == Cast->getOperand()) | |||
| 9070 | return Cast; // must be loop invariant | |||
| 9071 | return getPtrToIntExpr(Op, Cast->getType()); | |||
| 9072 | } | |||
| 9073 | ||||
| 9074 | llvm_unreachable("Unknown SCEV type!")__builtin_unreachable(); | |||
| 9075 | } | |||
| 9076 | ||||
| 9077 | const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) { | |||
| 9078 | return getSCEVAtScope(getSCEV(V), L); | |||
| 9079 | } | |||
| 9080 | ||||
| 9081 | const SCEV *ScalarEvolution::stripInjectiveFunctions(const SCEV *S) const { | |||
| 9082 | if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) | |||
| 9083 | return stripInjectiveFunctions(ZExt->getOperand()); | |||
| 9084 | if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) | |||
| 9085 | return stripInjectiveFunctions(SExt->getOperand()); | |||
| 9086 | return S; | |||
| 9087 | } | |||
| 9088 | ||||
| 9089 | /// Finds the minimum unsigned root of the following equation: | |||
| 9090 | /// | |||
| 9091 | /// A * X = B (mod N) | |||
| 9092 | /// | |||
| 9093 | /// where N = 2^BW and BW is the common bit width of A and B. The signedness of | |||
| 9094 | /// A and B isn't important. | |||
| 9095 | /// | |||
| 9096 | /// If the equation does not have a solution, SCEVCouldNotCompute is returned. | |||
| 9097 | static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const SCEV *B, | |||
| 9098 | ScalarEvolution &SE) { | |||
| 9099 | uint32_t BW = A.getBitWidth(); | |||
| 9100 | assert(BW == SE.getTypeSizeInBits(B->getType()))((void)0); | |||
| 9101 | assert(A != 0 && "A must be non-zero.")((void)0); | |||
| 9102 | ||||
| 9103 | // 1. D = gcd(A, N) | |||
| 9104 | // | |||
| 9105 | // The gcd of A and N may have only one prime factor: 2. The number of | |||
| 9106 | // trailing zeros in A is its multiplicity | |||
| 9107 | uint32_t Mult2 = A.countTrailingZeros(); | |||
| 9108 | // D = 2^Mult2 | |||
| 9109 | ||||
| 9110 | // 2. Check if B is divisible by D. | |||
| 9111 | // | |||
| 9112 | // B is divisible by D if and only if the multiplicity of prime factor 2 for B | |||
| 9113 | // is not less than multiplicity of this prime factor for D. | |||
| 9114 | if (SE.GetMinTrailingZeros(B) < Mult2) | |||
| 9115 | return SE.getCouldNotCompute(); | |||
| 9116 | ||||
| 9117 | // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic | |||
| 9118 | // modulo (N / D). | |||
| 9119 | // | |||
| 9120 | // If D == 1, (N / D) == N == 2^BW, so we need one extra bit to represent | |||
| 9121 | // (N / D) in general. The inverse itself always fits into BW bits, though, | |||
| 9122 | // so we immediately truncate it. | |||
| 9123 | APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D | |||
| 9124 | APInt Mod(BW + 1, 0); | |||
| 9125 | Mod.setBit(BW - Mult2); // Mod = N / D | |||
| 9126 | APInt I = AD.multiplicativeInverse(Mod).trunc(BW); | |||
| 9127 | ||||
| 9128 | // 4. Compute the minimum unsigned root of the equation: | |||
| 9129 | // I * (B / D) mod (N / D) | |||
| 9130 | // To simplify the computation, we factor out the divide by D: | |||
| 9131 | // (I * B mod N) / D | |||
| 9132 | const SCEV *D = SE.getConstant(APInt::getOneBitSet(BW, Mult2)); | |||
| 9133 | return SE.getUDivExactExpr(SE.getMulExpr(B, SE.getConstant(I)), D); | |||
| 9134 | } | |||
| 9135 | ||||
| 9136 | /// For a given quadratic addrec, generate coefficients of the corresponding | |||
| 9137 | /// quadratic equation, multiplied by a common value to ensure that they are | |||
| 9138 | /// integers. | |||
| 9139 | /// The returned value is a tuple { A, B, C, M, BitWidth }, where | |||
| 9140 | /// Ax^2 + Bx + C is the quadratic function, M is the value that A, B and C | |||
| 9141 | /// were multiplied by, and BitWidth is the bit width of the original addrec | |||
| 9142 | /// coefficients. | |||
| 9143 | /// This function returns None if the addrec coefficients are not compile- | |||
| 9144 | /// time constants. | |||
| 9145 | static Optional<std::tuple<APInt, APInt, APInt, APInt, unsigned>> | |||
| 9146 | GetQuadraticEquation(const SCEVAddRecExpr *AddRec) { | |||
| 9147 | assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!")((void)0); | |||
| 9148 | const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0)); | |||
| 9149 | const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1)); | |||
| 9150 | const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2)); | |||
| 9151 | LLVM_DEBUG(dbgs() << __func__ << ": analyzing quadratic addrec: "do { } while (false) | |||
| 9152 | << *AddRec << '\n')do { } while (false); | |||
| 9153 | ||||
| 9154 | // We currently can only solve this if the coefficients are constants. | |||
| 9155 | if (!LC || !MC || !NC) { | |||
| 9156 | LLVM_DEBUG(dbgs() << __func__ << ": coefficients are not constant\n")do { } while (false); | |||
| 9157 | return None; | |||
| 9158 | } | |||
| 9159 | ||||
| 9160 | APInt L = LC->getAPInt(); | |||
| 9161 | APInt M = MC->getAPInt(); | |||
| 9162 | APInt N = NC->getAPInt(); | |||
| 9163 | assert(!N.isNullValue() && "This is not a quadratic addrec")((void)0); | |||
| 9164 | ||||
| 9165 | unsigned BitWidth = LC->getAPInt().getBitWidth(); | |||
| 9166 | unsigned NewWidth = BitWidth + 1; | |||
| 9167 | LLVM_DEBUG(dbgs() << __func__ << ": addrec coeff bw: "do { } while (false) | |||
| 9168 | << BitWidth << '\n')do { } while (false); | |||
| 9169 | // The sign-extension (as opposed to a zero-extension) here matches the | |||
| 9170 | // extension used in SolveQuadraticEquationWrap (with the same motivation). | |||
| 9171 | N = N.sext(NewWidth); | |||
| 9172 | M = M.sext(NewWidth); | |||
| 9173 | L = L.sext(NewWidth); | |||
| 9174 | ||||
| 9175 | // The increments are M, M+N, M+2N, ..., so the accumulated values are | |||
| 9176 | // L+M, (L+M)+(M+N), (L+M)+(M+N)+(M+2N), ..., that is, | |||
| 9177 | // L+M, L+2M+N, L+3M+3N, ... | |||
| 9178 | // After n iterations the accumulated value Acc is L + nM + n(n-1)/2 N. | |||
| 9179 | // | |||
| 9180 | // The equation Acc = 0 is then | |||
| 9181 | // L + nM + n(n-1)/2 N = 0, or 2L + 2M n + n(n-1) N = 0. | |||
| 9182 | // In a quadratic form it becomes: | |||
| 9183 | // N n^2 + (2M-N) n + 2L = 0. | |||
| 9184 | ||||
| 9185 | APInt A = N; | |||
| 9186 | APInt B = 2 * M - A; | |||
| 9187 | APInt C = 2 * L; | |||
| 9188 | APInt T = APInt(NewWidth, 2); | |||
| 9189 | LLVM_DEBUG(dbgs() << __func__ << ": equation " << A << "x^2 + " << Bdo { } while (false) | |||
| 9190 | << "x + " << C << ", coeff bw: " << NewWidthdo { } while (false) | |||
| 9191 | << ", multiplied by " << T << '\n')do { } while (false); | |||
| 9192 | return std::make_tuple(A, B, C, T, BitWidth); | |||
| 9193 | } | |||
| 9194 | ||||
| 9195 | /// Helper function to compare optional APInts: | |||
| 9196 | /// (a) if X and Y both exist, return min(X, Y), | |||
| 9197 | /// (b) if neither X nor Y exist, return None, | |||
| 9198 | /// (c) if exactly one of X and Y exists, return that value. | |||
| 9199 | static Optional<APInt> MinOptional(Optional<APInt> X, Optional<APInt> Y) { | |||
| 9200 | if (X.hasValue() && Y.hasValue()) { | |||
| 9201 | unsigned W = std::max(X->getBitWidth(), Y->getBitWidth()); | |||
| 9202 | APInt XW = X->sextOrSelf(W); | |||
| 9203 | APInt YW = Y->sextOrSelf(W); | |||
| 9204 | return XW.slt(YW) ? *X : *Y; | |||
| 9205 | } | |||
| 9206 | if (!X.hasValue() && !Y.hasValue()) | |||
| 9207 | return None; | |||
| 9208 | return X.hasValue() ? *X : *Y; | |||
| 9209 | } | |||
| 9210 | ||||
| 9211 | /// Helper function to truncate an optional APInt to a given BitWidth. | |||
| 9212 | /// When solving addrec-related equations, it is preferable to return a value | |||
| 9213 | /// that has the same bit width as the original addrec's coefficients. If the | |||
| 9214 | /// solution fits in the original bit width, truncate it (except for i1). | |||
| 9215 | /// Returning a value of a different bit width may inhibit some optimizations. | |||
| 9216 | /// | |||
| 9217 | /// In general, a solution to a quadratic equation generated from an addrec | |||
| 9218 | /// may require BW+1 bits, where BW is the bit width of the addrec's | |||
| 9219 | /// coefficients. The reason is that the coefficients of the quadratic | |||
| 9220 | /// equation are BW+1 bits wide (to avoid truncation when converting from | |||
| 9221 | /// the addrec to the equation). | |||
| 9222 | static Optional<APInt> TruncIfPossible(Optional<APInt> X, unsigned BitWidth) { | |||
| 9223 | if (!X.hasValue()) | |||
| 9224 | return None; | |||
| 9225 | unsigned W = X->getBitWidth(); | |||
| 9226 | if (BitWidth > 1 && BitWidth < W && X->isIntN(BitWidth)) | |||
| 9227 | return X->trunc(BitWidth); | |||
| 9228 | return X; | |||
| 9229 | } | |||
| 9230 | ||||
| 9231 | /// Let c(n) be the value of the quadratic chrec {L,+,M,+,N} after n | |||
| 9232 | /// iterations. The values L, M, N are assumed to be signed, and they | |||
| 9233 | /// should all have the same bit widths. | |||
| 9234 | /// Find the least n >= 0 such that c(n) = 0 in the arithmetic modulo 2^BW, | |||
| 9235 | /// where BW is the bit width of the addrec's coefficients. | |||
| 9236 | /// If the calculated value is a BW-bit integer (for BW > 1), it will be | |||
| 9237 | /// returned as such, otherwise the bit width of the returned value may | |||
| 9238 | /// be greater than BW. | |||
| 9239 | /// | |||
| 9240 | /// This function returns None if | |||
| 9241 | /// (a) the addrec coefficients are not constant, or | |||
| 9242 | /// (b) SolveQuadraticEquationWrap was unable to find a solution. For cases | |||
| 9243 | /// like x^2 = 5, no integer solutions exist, in other cases an integer | |||
| 9244 | /// solution may exist, but SolveQuadraticEquationWrap may fail to find it. | |||
| 9245 | static Optional<APInt> | |||
| 9246 | SolveQuadraticAddRecExact(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) { | |||
| 9247 | APInt A, B, C, M; | |||
| 9248 | unsigned BitWidth; | |||
| 9249 | auto T = GetQuadraticEquation(AddRec); | |||
| 9250 | if (!T.hasValue()) | |||
| 9251 | return None; | |||
| 9252 | ||||
| 9253 | std::tie(A, B, C, M, BitWidth) = *T; | |||
| 9254 | LLVM_DEBUG(dbgs() << __func__ << ": solving for unsigned overflow\n")do { } while (false); | |||
| 9255 | Optional<APInt> X = APIntOps::SolveQuadraticEquationWrap(A, B, C, BitWidth+1); | |||
| 9256 | if (!X.hasValue()) | |||
| 9257 | return None; | |||
| 9258 | ||||
| 9259 | ConstantInt *CX = ConstantInt::get(SE.getContext(), *X); | |||
| 9260 | ConstantInt *V = EvaluateConstantChrecAtConstant(AddRec, CX, SE); | |||
| 9261 | if (!V->isZero()) | |||
| 9262 | return None; | |||
| 9263 | ||||
| 9264 | return TruncIfPossible(X, BitWidth); | |||
| 9265 | } | |||
| 9266 | ||||
| 9267 | /// Let c(n) be the value of the quadratic chrec {0,+,M,+,N} after n | |||
| 9268 | /// iterations. The values M, N are assumed to be signed, and they | |||
| 9269 | /// should all have the same bit widths. | |||
| 9270 | /// Find the least n such that c(n) does not belong to the given range, | |||
| 9271 | /// while c(n-1) does. | |||
| 9272 | /// | |||
| 9273 | /// This function returns None if | |||
| 9274 | /// (a) the addrec coefficients are not constant, or | |||
| 9275 | /// (b) SolveQuadraticEquationWrap was unable to find a solution for the | |||
| 9276 | /// bounds of the range. | |||
| 9277 | static Optional<APInt> | |||
| 9278 | SolveQuadraticAddRecRange(const SCEVAddRecExpr *AddRec, | |||
| 9279 | const ConstantRange &Range, ScalarEvolution &SE) { | |||
| 9280 | assert(AddRec->getOperand(0)->isZero() &&((void)0) | |||
| 9281 | "Starting value of addrec should be 0")((void)0); | |||
| 9282 | LLVM_DEBUG(dbgs() << __func__ << ": solving boundary crossing for range "do { } while (false) | |||
| 9283 | << Range << ", addrec " << *AddRec << '\n')do { } while (false); | |||
| 9284 | // This case is handled in getNumIterationsInRange. Here we can assume that | |||
| 9285 | // we start in the range. | |||
| 9286 | assert(Range.contains(APInt(SE.getTypeSizeInBits(AddRec->getType()), 0)) &&((void)0) | |||
| 9287 | "Addrec's initial value should be in range")((void)0); | |||
| 9288 | ||||
| 9289 | APInt A, B, C, M; | |||
| 9290 | unsigned BitWidth; | |||
| 9291 | auto T = GetQuadraticEquation(AddRec); | |||
| 9292 | if (!T.hasValue()) | |||
| 9293 | return None; | |||
| 9294 | ||||
| 9295 | // Be careful about the return value: there can be two reasons for not | |||
| 9296 | // returning an actual number. First, if no solutions to the equations | |||
| 9297 | // were found, and second, if the solutions don't leave the given range. | |||
| 9298 | // The first case means that the actual solution is "unknown", the second | |||
| 9299 | // means that it's known, but not valid. If the solution is unknown, we | |||
| 9300 | // cannot make any conclusions. | |||
| 9301 | // Return a pair: the optional solution and a flag indicating if the | |||
| 9302 | // solution was found. | |||
| 9303 | auto SolveForBoundary = [&](APInt Bound) -> std::pair<Optional<APInt>,bool> { | |||
| 9304 | // Solve for signed overflow and unsigned overflow, pick the lower | |||
| 9305 | // solution. | |||
| 9306 | LLVM_DEBUG(dbgs() << "SolveQuadraticAddRecRange: checking boundary "do { } while (false) | |||
| 9307 | << Bound << " (before multiplying by " << M << ")\n")do { } while (false); | |||
| 9308 | Bound *= M; // The quadratic equation multiplier. | |||
| 9309 | ||||
| 9310 | Optional<APInt> SO = None; | |||
| 9311 | if (BitWidth > 1) { | |||
| 9312 | LLVM_DEBUG(dbgs() << "SolveQuadraticAddRecRange: solving for "do { } while (false) | |||
| 9313 | "signed overflow\n")do { } while (false); | |||
| 9314 | SO = APIntOps::SolveQuadraticEquationWrap(A, B, -Bound, BitWidth); | |||
| 9315 | } | |||
| 9316 | LLVM_DEBUG(dbgs() << "SolveQuadraticAddRecRange: solving for "do { } while (false) | |||
| 9317 | "unsigned overflow\n")do { } while (false); | |||
| 9318 | Optional<APInt> UO = APIntOps::SolveQuadraticEquationWrap(A, B, -Bound, | |||
| 9319 | BitWidth+1); | |||
| 9320 | ||||
| 9321 | auto LeavesRange = [&] (const APInt &X) { | |||
| 9322 | ConstantInt *C0 = ConstantInt::get(SE.getContext(), X); | |||
| 9323 | ConstantInt *V0 = EvaluateConstantChrecAtConstant(AddRec, C0, SE); | |||
| 9324 | if (Range.contains(V0->getValue())) | |||
| 9325 | return false; | |||
| 9326 | // X should be at least 1, so X-1 is non-negative. | |||
| 9327 | ConstantInt *C1 = ConstantInt::get(SE.getContext(), X-1); | |||
| 9328 | ConstantInt *V1 = EvaluateConstantChrecAtConstant(AddRec, C1, SE); | |||
| 9329 | if (Range.contains(V1->getValue())) | |||
| 9330 | return true; | |||
| 9331 | return false; | |||
| 9332 | }; | |||
| 9333 | ||||
| 9334 | // If SolveQuadraticEquationWrap returns None, it means that there can | |||
| 9335 | // be a solution, but the function failed to find it. We cannot treat it | |||
| 9336 | // as "no solution". | |||
| 9337 | if (!SO.hasValue() || !UO.hasValue()) | |||
| 9338 | return { None, false }; | |||
| 9339 | ||||
| 9340 | // Check the smaller value first to see if it leaves the range. | |||
| 9341 | // At this point, both SO and UO must have values. | |||
| 9342 | Optional<APInt> Min = MinOptional(SO, UO); | |||
| 9343 | if (LeavesRange(*Min)) | |||
| 9344 | return { Min, true }; | |||
| 9345 | Optional<APInt> Max = Min == SO ? UO : SO; | |||
| 9346 | if (LeavesRange(*Max)) | |||
| 9347 | return { Max, true }; | |||
| 9348 | ||||
| 9349 | // Solutions were found, but were eliminated, hence the "true". | |||
| 9350 | return { None, true }; | |||
| 9351 | }; | |||
| 9352 | ||||
| 9353 | std::tie(A, B, C, M, BitWidth) = *T; | |||
| 9354 | // Lower bound is inclusive, subtract 1 to represent the exiting value. | |||
| 9355 | APInt Lower = Range.getLower().sextOrSelf(A.getBitWidth()) - 1; | |||
| 9356 | APInt Upper = Range.getUpper().sextOrSelf(A.getBitWidth()); | |||
| 9357 | auto SL = SolveForBoundary(Lower); | |||
| 9358 | auto SU = SolveForBoundary(Upper); | |||
| 9359 | // If any of the solutions was unknown, no meaninigful conclusions can | |||
| 9360 | // be made. | |||
| 9361 | if (!SL.second || !SU.second) | |||
| 9362 | return None; | |||
| 9363 | ||||
| 9364 | // Claim: The correct solution is not some value between Min and Max. | |||
| 9365 | // | |||
| 9366 | // Justification: Assuming that Min and Max are different values, one of | |||
| 9367 | // them is when the first signed overflow happens, the other is when the | |||
| 9368 | // first unsigned overflow happens. Crossing the range boundary is only | |||
| 9369 | // possible via an overflow (treating 0 as a special case of it, modeling | |||
| 9370 | // an overflow as crossing k*2^W for some k). | |||
| 9371 | // | |||
| 9372 | // The interesting case here is when Min was eliminated as an invalid | |||
| 9373 | // solution, but Max was not. The argument is that if there was another | |||
| 9374 | // overflow between Min and Max, it would also have been eliminated if | |||
| 9375 | // it was considered. | |||
| 9376 | // | |||
| 9377 | // For a given boundary, it is possible to have two overflows of the same | |||
| 9378 | // type (signed/unsigned) without having the other type in between: this | |||
| 9379 | // can happen when the vertex of the parabola is between the iterations | |||
| 9380 | // corresponding to the overflows. This is only possible when the two | |||
| 9381 | // overflows cross k*2^W for the same k. In such case, if the second one | |||
| 9382 | // left the range (and was the first one to do so), the first overflow | |||
| 9383 | // would have to enter the range, which would mean that either we had left | |||
| 9384 | // the range before or that we started outside of it. Both of these cases | |||
| 9385 | // are contradictions. | |||
| 9386 | // | |||
| 9387 | // Claim: In the case where SolveForBoundary returns None, the correct | |||
| 9388 | // solution is not some value between the Max for this boundary and the | |||
| 9389 | // Min of the other boundary. | |||
| 9390 | // | |||
| 9391 | // Justification: Assume that we had such Max_A and Min_B corresponding | |||
| 9392 | // to range boundaries A and B and such that Max_A < Min_B. If there was | |||
| 9393 | // a solution between Max_A and Min_B, it would have to be caused by an | |||
| 9394 | // overflow corresponding to either A or B. It cannot correspond to B, | |||
| 9395 | // since Min_B is the first occurrence of such an overflow. If it | |||
| 9396 | // corresponded to A, it would have to be either a signed or an unsigned | |||
| 9397 | // overflow that is larger than both eliminated overflows for A. But | |||
| 9398 | // between the eliminated overflows and this overflow, the values would | |||
| 9399 | // cover the entire value space, thus crossing the other boundary, which | |||
| 9400 | // is a contradiction. | |||
| 9401 | ||||
| 9402 | return TruncIfPossible(MinOptional(SL.first, SU.first), BitWidth); | |||
| 9403 | } | |||
| 9404 | ||||
| 9405 | ScalarEvolution::ExitLimit | |||
| 9406 | ScalarEvolution::howFarToZero(const SCEV *V, const Loop *L, bool ControlsExit, | |||
| 9407 | bool AllowPredicates) { | |||
| 9408 | ||||
| 9409 | // This is only used for loops with a "x != y" exit test. The exit condition | |||
| 9410 | // is now expressed as a single expression, V = x-y. So the exit test is | |||
| 9411 | // effectively V != 0. We know and take advantage of the fact that this | |||
| 9412 | // expression only being used in a comparison by zero context. | |||
| 9413 | ||||
| 9414 | SmallPtrSet<const SCEVPredicate *, 4> Predicates; | |||
| 9415 | // If the value is a constant | |||
| 9416 | if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) { | |||
| 9417 | // If the value is already zero, the branch will execute zero times. | |||
| 9418 | if (C->getValue()->isZero()) return C; | |||
| 9419 | return getCouldNotCompute(); // Otherwise it will loop infinitely. | |||
| 9420 | } | |||
| 9421 | ||||
| 9422 | const SCEVAddRecExpr *AddRec = | |||
| 9423 | dyn_cast<SCEVAddRecExpr>(stripInjectiveFunctions(V)); | |||
| 9424 | ||||
| 9425 | if (!AddRec && AllowPredicates) | |||
| 9426 | // Try to make this an AddRec using runtime tests, in the first X | |||
| 9427 | // iterations of this loop, where X is the SCEV expression found by the | |||
| 9428 | // algorithm below. | |||
| 9429 | AddRec = convertSCEVToAddRecWithPredicates(V, L, Predicates); | |||
| 9430 | ||||
| 9431 | if (!AddRec || AddRec->getLoop() != L) | |||
| 9432 | return getCouldNotCompute(); | |||
| 9433 | ||||
| 9434 | // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of | |||
| 9435 | // the quadratic equation to solve it. | |||
| 9436 | if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) { | |||
| 9437 | // We can only use this value if the chrec ends up with an exact zero | |||
| 9438 | // value at this index. When solving for "X*X != 5", for example, we | |||
| 9439 | // should not accept a root of 2. | |||
| 9440 | if (auto S = SolveQuadraticAddRecExact(AddRec, *this)) { | |||
| 9441 | const auto *R = cast<SCEVConstant>(getConstant(S.getValue())); | |||
| 9442 | return ExitLimit(R, R, false, Predicates); | |||
| 9443 | } | |||
| 9444 | return getCouldNotCompute(); | |||
| 9445 | } | |||
| 9446 | ||||
| 9447 | // Otherwise we can only handle this if it is affine. | |||
| 9448 | if (!AddRec->isAffine()) | |||
| 9449 | return getCouldNotCompute(); | |||
| 9450 | ||||
| 9451 | // If this is an affine expression, the execution count of this branch is | |||
| 9452 | // the minimum unsigned root of the following equation: | |||
| 9453 | // | |||
| 9454 | // Start + Step*N = 0 (mod 2^BW) | |||
| 9455 | // | |||
| 9456 | // equivalent to: | |||
| 9457 | // | |||
| 9458 | // Step*N = -Start (mod 2^BW) | |||
| 9459 | // | |||
| 9460 | // where BW is the common bit width of Start and Step. | |||
| 9461 | ||||
| 9462 | // Get the initial value for the loop. | |||
| 9463 | const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop()); | |||
| 9464 | const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop()); | |||
| 9465 | ||||
| 9466 | // For now we handle only constant steps. | |||
| 9467 | // | |||
| 9468 | // TODO: Handle a nonconstant Step given AddRec<NUW>. If the | |||
| 9469 | // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap | |||
| 9470 | // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step. | |||
| 9471 | // We have not yet seen any such cases. | |||
| 9472 | const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step); | |||
| 9473 | if (!StepC || StepC->getValue()->isZero()) | |||
| 9474 | return getCouldNotCompute(); | |||
| 9475 | ||||
| 9476 | // For positive steps (counting up until unsigned overflow): | |||
| 9477 | // N = -Start/Step (as unsigned) | |||
| 9478 | // For negative steps (counting down to zero): | |||
| 9479 | // N = Start/-Step | |||
| 9480 | // First compute the unsigned distance from zero in the direction of Step. | |||
| 9481 | bool CountDown = StepC->getAPInt().isNegative(); | |||
| 9482 | const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start); | |||
| 9483 | ||||
| 9484 | // Handle unitary steps, which cannot wraparound. | |||
| 9485 | // 1*N = -Start; -1*N = Start (mod 2^BW), so: | |||
| 9486 | // N = Distance (as unsigned) | |||
| 9487 | if (StepC->getValue()->isOne() || StepC->getValue()->isMinusOne()) { | |||
| 9488 | APInt MaxBECount = getUnsignedRangeMax(applyLoopGuards(Distance, L)); | |||
| 9489 | APInt MaxBECountBase = getUnsignedRangeMax(Distance); | |||
| 9490 | if (MaxBECountBase.ult(MaxBECount)) | |||
| 9491 | MaxBECount = MaxBECountBase; | |||
| 9492 | ||||
| 9493 | // When a loop like "for (int i = 0; i != n; ++i) { /* body */ }" is rotated, | |||
| 9494 | // we end up with a loop whose backedge-taken count is n - 1. Detect this | |||
| 9495 | // case, and see if we can improve the bound. | |||
| 9496 | // | |||
| 9497 | // Explicitly handling this here is necessary because getUnsignedRange | |||
| 9498 | // isn't context-sensitive; it doesn't know that we only care about the | |||
| 9499 | // range inside the loop. | |||
| 9500 | const SCEV *Zero = getZero(Distance->getType()); | |||
| 9501 | const SCEV *One = getOne(Distance->getType()); | |||
| 9502 | const SCEV *DistancePlusOne = getAddExpr(Distance, One); | |||
| 9503 | if (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, DistancePlusOne, Zero)) { | |||
| 9504 | // If Distance + 1 doesn't overflow, we can compute the maximum distance | |||
| 9505 | // as "unsigned_max(Distance + 1) - 1". | |||
| 9506 | ConstantRange CR = getUnsignedRange(DistancePlusOne); | |||
| 9507 | MaxBECount = APIntOps::umin(MaxBECount, CR.getUnsignedMax() - 1); | |||
| 9508 | } | |||
| 9509 | return ExitLimit(Distance, getConstant(MaxBECount), false, Predicates); | |||
| 9510 | } | |||
| 9511 | ||||
| 9512 | // If the condition controls loop exit (the loop exits only if the expression | |||
| 9513 | // is true) and the addition is no-wrap we can use unsigned divide to | |||
| 9514 | // compute the backedge count. In this case, the step may not divide the | |||
| 9515 | // distance, but we don't care because if the condition is "missed" the loop | |||
| 9516 | // will have undefined behavior due to wrapping. | |||
| 9517 | if (ControlsExit && AddRec->hasNoSelfWrap() && | |||
| 9518 | loopHasNoAbnormalExits(AddRec->getLoop())) { | |||
| 9519 | const SCEV *Exact = | |||
| 9520 | getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step); | |||
| 9521 | const SCEV *Max = getCouldNotCompute(); | |||
| 9522 | if (Exact != getCouldNotCompute()) { | |||
| 9523 | APInt MaxInt = getUnsignedRangeMax(applyLoopGuards(Exact, L)); | |||
| 9524 | APInt BaseMaxInt = getUnsignedRangeMax(Exact); | |||
| 9525 | if (BaseMaxInt.ult(MaxInt)) | |||
| 9526 | Max = getConstant(BaseMaxInt); | |||
| 9527 | else | |||
| 9528 | Max = getConstant(MaxInt); | |||
| 9529 | } | |||
| 9530 | return ExitLimit(Exact, Max, false, Predicates); | |||
| 9531 | } | |||
| 9532 | ||||
| 9533 | // Solve the general equation. | |||
| 9534 | const SCEV *E = SolveLinEquationWithOverflow(StepC->getAPInt(), | |||
| 9535 | getNegativeSCEV(Start), *this); | |||
| 9536 | const SCEV *M = E == getCouldNotCompute() | |||
| 9537 | ? E | |||
| 9538 | : getConstant(getUnsignedRangeMax(E)); | |||
| 9539 | return ExitLimit(E, M, false, Predicates); | |||
| 9540 | } | |||
| 9541 | ||||
| 9542 | ScalarEvolution::ExitLimit | |||
| 9543 | ScalarEvolution::howFarToNonZero(const SCEV *V, const Loop *L) { | |||
| 9544 | // Loops that look like: while (X == 0) are very strange indeed. We don't | |||
| 9545 | // handle them yet except for the trivial case. This could be expanded in the | |||
| 9546 | // future as needed. | |||
| 9547 | ||||
| 9548 | // If the value is a constant, check to see if it is known to be non-zero | |||
| 9549 | // already. If so, the backedge will execute zero times. | |||
| 9550 | if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) { | |||
| 9551 | if (!C->getValue()->isZero()) | |||
| 9552 | return getZero(C->getType()); | |||
| 9553 | return getCouldNotCompute(); // Otherwise it will loop infinitely. | |||
| 9554 | } | |||
| 9555 | ||||
| 9556 | // We could implement others, but I really doubt anyone writes loops like | |||
| 9557 | // this, and if they did, they would already be constant folded. | |||
| 9558 | return getCouldNotCompute(); | |||
| 9559 | } | |||
| 9560 | ||||
| 9561 | std::pair<const BasicBlock *, const BasicBlock *> | |||
| 9562 | ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(const BasicBlock *BB) | |||
| 9563 | const { | |||
| 9564 | // If the block has a unique predecessor, then there is no path from the | |||
| 9565 | // predecessor to the block that does not go through the direct edge | |||
| 9566 | // from the predecessor to the block. | |||
| 9567 | if (const BasicBlock *Pred = BB->getSinglePredecessor()) | |||
| 9568 | return {Pred, BB}; | |||
| 9569 | ||||
| 9570 | // A loop's header is defined to be a block that dominates the loop. | |||
| 9571 | // If the header has a unique predecessor outside the loop, it must be | |||
| 9572 | // a block that has exactly one successor that can reach the loop. | |||
| 9573 | if (const Loop *L = LI.getLoopFor(BB)) | |||
| 9574 | return {L->getLoopPredecessor(), L->getHeader()}; | |||
| 9575 | ||||
| 9576 | return {nullptr, nullptr}; | |||
| 9577 | } | |||
| 9578 | ||||
| 9579 | /// SCEV structural equivalence is usually sufficient for testing whether two | |||
| 9580 | /// expressions are equal, however for the purposes of looking for a condition | |||
| 9581 | /// guarding a loop, it can be useful to be a little more general, since a | |||
| 9582 | /// front-end may have replicated the controlling expression. | |||
| 9583 | static bool HasSameValue(const SCEV *A, const SCEV *B) { | |||
| 9584 | // Quick check to see if they are the same SCEV. | |||
| 9585 | if (A == B) return true; | |||
| 9586 | ||||
| 9587 | auto ComputesEqualValues = [](const Instruction *A, const Instruction *B) { | |||
| 9588 | // Not all instructions that are "identical" compute the same value. For | |||
| 9589 | // instance, two distinct alloca instructions allocating the same type are | |||
| 9590 | // identical and do not read memory; but compute distinct values. | |||
| 9591 | return A->isIdenticalTo(B) && (isa<BinaryOperator>(A) || isa<GetElementPtrInst>(A)); | |||
| 9592 | }; | |||
| 9593 | ||||
| 9594 | // Otherwise, if they're both SCEVUnknown, it's possible that they hold | |||
| 9595 | // two different instructions with the same value. Check for this case. | |||
| 9596 | if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A)) | |||
| 9597 | if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B)) | |||
| 9598 | if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue())) | |||
| 9599 | if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue())) | |||
| 9600 | if (ComputesEqualValues(AI, BI)) | |||
| 9601 | return true; | |||
| 9602 | ||||
| 9603 | // Otherwise assume they may have a different value. | |||
| 9604 | return false; | |||
| 9605 | } | |||
| 9606 | ||||
| 9607 | bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred, | |||
| 9608 | const SCEV *&LHS, const SCEV *&RHS, | |||
| 9609 | unsigned Depth) { | |||
| 9610 | bool Changed = false; | |||
| 9611 | // Simplifies ICMP to trivial true or false by turning it into '0 == 0' or | |||
| 9612 | // '0 != 0'. | |||
| 9613 | auto TrivialCase = [&](bool TriviallyTrue) { | |||
| 9614 | LHS = RHS = getConstant(ConstantInt::getFalse(getContext())); | |||
| 9615 | Pred = TriviallyTrue ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE; | |||
| 9616 | return true; | |||
| 9617 | }; | |||
| 9618 | // If we hit the max recursion limit bail out. | |||
| 9619 | if (Depth >= 3) | |||
| 9620 | return false; | |||
| 9621 | ||||
| 9622 | // Canonicalize a constant to the right side. | |||
| 9623 | if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) { | |||
| 9624 | // Check for both operands constant. | |||
| 9625 | if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) { | |||
| 9626 | if (ConstantExpr::getICmp(Pred, | |||
| 9627 | LHSC->getValue(), | |||
| 9628 | RHSC->getValue())->isNullValue()) | |||
| 9629 | return TrivialCase(false); | |||
| 9630 | else | |||
| 9631 | return TrivialCase(true); | |||
| 9632 | } | |||
| 9633 | // Otherwise swap the operands to put the constant on the right. | |||
| 9634 | std::swap(LHS, RHS); | |||
| 9635 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 9636 | Changed = true; | |||
| 9637 | } | |||
| 9638 | ||||
| 9639 | // If we're comparing an addrec with a value which is loop-invariant in the | |||
| 9640 | // addrec's loop, put the addrec on the left. Also make a dominance check, | |||
| 9641 | // as both operands could be addrecs loop-invariant in each other's loop. | |||
| 9642 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) { | |||
| 9643 | const Loop *L = AR->getLoop(); | |||
| 9644 | if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) { | |||
| 9645 | std::swap(LHS, RHS); | |||
| 9646 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 9647 | Changed = true; | |||
| 9648 | } | |||
| 9649 | } | |||
| 9650 | ||||
| 9651 | // If there's a constant operand, canonicalize comparisons with boundary | |||
| 9652 | // cases, and canonicalize *-or-equal comparisons to regular comparisons. | |||
| 9653 | if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) { | |||
| 9654 | const APInt &RA = RC->getAPInt(); | |||
| 9655 | ||||
| 9656 | bool SimplifiedByConstantRange = false; | |||
| 9657 | ||||
| 9658 | if (!ICmpInst::isEquality(Pred)) { | |||
| 9659 | ConstantRange ExactCR = ConstantRange::makeExactICmpRegion(Pred, RA); | |||
| 9660 | if (ExactCR.isFullSet()) | |||
| 9661 | return TrivialCase(true); | |||
| 9662 | else if (ExactCR.isEmptySet()) | |||
| 9663 | return TrivialCase(false); | |||
| 9664 | ||||
| 9665 | APInt NewRHS; | |||
| 9666 | CmpInst::Predicate NewPred; | |||
| 9667 | if (ExactCR.getEquivalentICmp(NewPred, NewRHS) && | |||
| 9668 | ICmpInst::isEquality(NewPred)) { | |||
| 9669 | // We were able to convert an inequality to an equality. | |||
| 9670 | Pred = NewPred; | |||
| 9671 | RHS = getConstant(NewRHS); | |||
| 9672 | Changed = SimplifiedByConstantRange = true; | |||
| 9673 | } | |||
| 9674 | } | |||
| 9675 | ||||
| 9676 | if (!SimplifiedByConstantRange) { | |||
| 9677 | switch (Pred) { | |||
| 9678 | default: | |||
| 9679 | break; | |||
| 9680 | case ICmpInst::ICMP_EQ: | |||
| 9681 | case ICmpInst::ICMP_NE: | |||
| 9682 | // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b. | |||
| 9683 | if (!RA) | |||
| 9684 | if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS)) | |||
| 9685 | if (const SCEVMulExpr *ME = | |||
| 9686 | dyn_cast<SCEVMulExpr>(AE->getOperand(0))) | |||
| 9687 | if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 && | |||
| 9688 | ME->getOperand(0)->isAllOnesValue()) { | |||
| 9689 | RHS = AE->getOperand(1); | |||
| 9690 | LHS = ME->getOperand(1); | |||
| 9691 | Changed = true; | |||
| 9692 | } | |||
| 9693 | break; | |||
| 9694 | ||||
| 9695 | ||||
| 9696 | // The "Should have been caught earlier!" messages refer to the fact | |||
| 9697 | // that the ExactCR.isFullSet() or ExactCR.isEmptySet() check above | |||
| 9698 | // should have fired on the corresponding cases, and canonicalized the | |||
| 9699 | // check to trivial case. | |||
| 9700 | ||||
| 9701 | case ICmpInst::ICMP_UGE: | |||
| 9702 | assert(!RA.isMinValue() && "Should have been caught earlier!")((void)0); | |||
| 9703 | Pred = ICmpInst::ICMP_UGT; | |||
| 9704 | RHS = getConstant(RA - 1); | |||
| 9705 | Changed = true; | |||
| 9706 | break; | |||
| 9707 | case ICmpInst::ICMP_ULE: | |||
| 9708 | assert(!RA.isMaxValue() && "Should have been caught earlier!")((void)0); | |||
| 9709 | Pred = ICmpInst::ICMP_ULT; | |||
| 9710 | RHS = getConstant(RA + 1); | |||
| 9711 | Changed = true; | |||
| 9712 | break; | |||
| 9713 | case ICmpInst::ICMP_SGE: | |||
| 9714 | assert(!RA.isMinSignedValue() && "Should have been caught earlier!")((void)0); | |||
| 9715 | Pred = ICmpInst::ICMP_SGT; | |||
| 9716 | RHS = getConstant(RA - 1); | |||
| 9717 | Changed = true; | |||
| 9718 | break; | |||
| 9719 | case ICmpInst::ICMP_SLE: | |||
| 9720 | assert(!RA.isMaxSignedValue() && "Should have been caught earlier!")((void)0); | |||
| 9721 | Pred = ICmpInst::ICMP_SLT; | |||
| 9722 | RHS = getConstant(RA + 1); | |||
| 9723 | Changed = true; | |||
| 9724 | break; | |||
| 9725 | } | |||
| 9726 | } | |||
| 9727 | } | |||
| 9728 | ||||
| 9729 | // Check for obvious equality. | |||
| 9730 | if (HasSameValue(LHS, RHS)) { | |||
| 9731 | if (ICmpInst::isTrueWhenEqual(Pred)) | |||
| 9732 | return TrivialCase(true); | |||
| 9733 | if (ICmpInst::isFalseWhenEqual(Pred)) | |||
| 9734 | return TrivialCase(false); | |||
| 9735 | } | |||
| 9736 | ||||
| 9737 | // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by | |||
| 9738 | // adding or subtracting 1 from one of the operands. | |||
| 9739 | switch (Pred) { | |||
| 9740 | case ICmpInst::ICMP_SLE: | |||
| 9741 | if (!getSignedRangeMax(RHS).isMaxSignedValue()) { | |||
| 9742 | RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS, | |||
| 9743 | SCEV::FlagNSW); | |||
| 9744 | Pred = ICmpInst::ICMP_SLT; | |||
| 9745 | Changed = true; | |||
| 9746 | } else if (!getSignedRangeMin(LHS).isMinSignedValue()) { | |||
| 9747 | LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS, | |||
| 9748 | SCEV::FlagNSW); | |||
| 9749 | Pred = ICmpInst::ICMP_SLT; | |||
| 9750 | Changed = true; | |||
| 9751 | } | |||
| 9752 | break; | |||
| 9753 | case ICmpInst::ICMP_SGE: | |||
| 9754 | if (!getSignedRangeMin(RHS).isMinSignedValue()) { | |||
| 9755 | RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS, | |||
| 9756 | SCEV::FlagNSW); | |||
| 9757 | Pred = ICmpInst::ICMP_SGT; | |||
| 9758 | Changed = true; | |||
| 9759 | } else if (!getSignedRangeMax(LHS).isMaxSignedValue()) { | |||
| 9760 | LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS, | |||
| 9761 | SCEV::FlagNSW); | |||
| 9762 | Pred = ICmpInst::ICMP_SGT; | |||
| 9763 | Changed = true; | |||
| 9764 | } | |||
| 9765 | break; | |||
| 9766 | case ICmpInst::ICMP_ULE: | |||
| 9767 | if (!getUnsignedRangeMax(RHS).isMaxValue()) { | |||
| 9768 | RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS, | |||
| 9769 | SCEV::FlagNUW); | |||
| 9770 | Pred = ICmpInst::ICMP_ULT; | |||
| 9771 | Changed = true; | |||
| 9772 | } else if (!getUnsignedRangeMin(LHS).isMinValue()) { | |||
| 9773 | LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS); | |||
| 9774 | Pred = ICmpInst::ICMP_ULT; | |||
| 9775 | Changed = true; | |||
| 9776 | } | |||
| 9777 | break; | |||
| 9778 | case ICmpInst::ICMP_UGE: | |||
| 9779 | if (!getUnsignedRangeMin(RHS).isMinValue()) { | |||
| 9780 | RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS); | |||
| 9781 | Pred = ICmpInst::ICMP_UGT; | |||
| 9782 | Changed = true; | |||
| 9783 | } else if (!getUnsignedRangeMax(LHS).isMaxValue()) { | |||
| 9784 | LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS, | |||
| 9785 | SCEV::FlagNUW); | |||
| 9786 | Pred = ICmpInst::ICMP_UGT; | |||
| 9787 | Changed = true; | |||
| 9788 | } | |||
| 9789 | break; | |||
| 9790 | default: | |||
| 9791 | break; | |||
| 9792 | } | |||
| 9793 | ||||
| 9794 | // TODO: More simplifications are possible here. | |||
| 9795 | ||||
| 9796 | // Recursively simplify until we either hit a recursion limit or nothing | |||
| 9797 | // changes. | |||
| 9798 | if (Changed) | |||
| 9799 | return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1); | |||
| 9800 | ||||
| 9801 | return Changed; | |||
| 9802 | } | |||
| 9803 | ||||
| 9804 | bool ScalarEvolution::isKnownNegative(const SCEV *S) { | |||
| 9805 | return getSignedRangeMax(S).isNegative(); | |||
| 9806 | } | |||
| 9807 | ||||
| 9808 | bool ScalarEvolution::isKnownPositive(const SCEV *S) { | |||
| 9809 | return getSignedRangeMin(S).isStrictlyPositive(); | |||
| 9810 | } | |||
| 9811 | ||||
| 9812 | bool ScalarEvolution::isKnownNonNegative(const SCEV *S) { | |||
| 9813 | return !getSignedRangeMin(S).isNegative(); | |||
| 9814 | } | |||
| 9815 | ||||
| 9816 | bool ScalarEvolution::isKnownNonPositive(const SCEV *S) { | |||
| 9817 | return !getSignedRangeMax(S).isStrictlyPositive(); | |||
| 9818 | } | |||
| 9819 | ||||
| 9820 | bool ScalarEvolution::isKnownNonZero(const SCEV *S) { | |||
| 9821 | return getUnsignedRangeMin(S) != 0; | |||
| 9822 | } | |||
| 9823 | ||||
| 9824 | std::pair<const SCEV *, const SCEV *> | |||
| 9825 | ScalarEvolution::SplitIntoInitAndPostInc(const Loop *L, const SCEV *S) { | |||
| 9826 | // Compute SCEV on entry of loop L. | |||
| 9827 | const SCEV *Start = SCEVInitRewriter::rewrite(S, L, *this); | |||
| 9828 | if (Start == getCouldNotCompute()) | |||
| 9829 | return { Start, Start }; | |||
| 9830 | // Compute post increment SCEV for loop L. | |||
| 9831 | const SCEV *PostInc = SCEVPostIncRewriter::rewrite(S, L, *this); | |||
| 9832 | assert(PostInc != getCouldNotCompute() && "Unexpected could not compute")((void)0); | |||
| 9833 | return { Start, PostInc }; | |||
| 9834 | } | |||
| 9835 | ||||
| 9836 | bool ScalarEvolution::isKnownViaInduction(ICmpInst::Predicate Pred, | |||
| 9837 | const SCEV *LHS, const SCEV *RHS) { | |||
| 9838 | // First collect all loops. | |||
| 9839 | SmallPtrSet<const Loop *, 8> LoopsUsed; | |||
| 9840 | getUsedLoops(LHS, LoopsUsed); | |||
| 9841 | getUsedLoops(RHS, LoopsUsed); | |||
| 9842 | ||||
| 9843 | if (LoopsUsed.empty()) | |||
| 9844 | return false; | |||
| 9845 | ||||
| 9846 | // Domination relationship must be a linear order on collected loops. | |||
| 9847 | #ifndef NDEBUG1 | |||
| 9848 | for (auto *L1 : LoopsUsed) | |||
| 9849 | for (auto *L2 : LoopsUsed) | |||
| 9850 | assert((DT.dominates(L1->getHeader(), L2->getHeader()) ||((void)0) | |||
| 9851 | DT.dominates(L2->getHeader(), L1->getHeader())) &&((void)0) | |||
| 9852 | "Domination relationship is not a linear order")((void)0); | |||
| 9853 | #endif | |||
| 9854 | ||||
| 9855 | const Loop *MDL = | |||
| 9856 | *std::max_element(LoopsUsed.begin(), LoopsUsed.end(), | |||
| 9857 | [&](const Loop *L1, const Loop *L2) { | |||
| 9858 | return DT.properlyDominates(L1->getHeader(), L2->getHeader()); | |||
| 9859 | }); | |||
| 9860 | ||||
| 9861 | // Get init and post increment value for LHS. | |||
| 9862 | auto SplitLHS = SplitIntoInitAndPostInc(MDL, LHS); | |||
| 9863 | // if LHS contains unknown non-invariant SCEV then bail out. | |||
| 9864 | if (SplitLHS.first == getCouldNotCompute()) | |||
| 9865 | return false; | |||
| 9866 | assert (SplitLHS.second != getCouldNotCompute() && "Unexpected CNC")((void)0); | |||
| 9867 | // Get init and post increment value for RHS. | |||
| 9868 | auto SplitRHS = SplitIntoInitAndPostInc(MDL, RHS); | |||
| 9869 | // if RHS contains unknown non-invariant SCEV then bail out. | |||
| 9870 | if (SplitRHS.first == getCouldNotCompute()) | |||
| 9871 | return false; | |||
| 9872 | assert (SplitRHS.second != getCouldNotCompute() && "Unexpected CNC")((void)0); | |||
| 9873 | // It is possible that init SCEV contains an invariant load but it does | |||
| 9874 | // not dominate MDL and is not available at MDL loop entry, so we should | |||
| 9875 | // check it here. | |||
| 9876 | if (!isAvailableAtLoopEntry(SplitLHS.first, MDL) || | |||
| 9877 | !isAvailableAtLoopEntry(SplitRHS.first, MDL)) | |||
| 9878 | return false; | |||
| 9879 | ||||
| 9880 | // It seems backedge guard check is faster than entry one so in some cases | |||
| 9881 | // it can speed up whole estimation by short circuit | |||
| 9882 | return isLoopBackedgeGuardedByCond(MDL, Pred, SplitLHS.second, | |||
| 9883 | SplitRHS.second) && | |||
| 9884 | isLoopEntryGuardedByCond(MDL, Pred, SplitLHS.first, SplitRHS.first); | |||
| 9885 | } | |||
| 9886 | ||||
| 9887 | bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred, | |||
| 9888 | const SCEV *LHS, const SCEV *RHS) { | |||
| 9889 | // Canonicalize the inputs first. | |||
| 9890 | (void)SimplifyICmpOperands(Pred, LHS, RHS); | |||
| 9891 | ||||
| 9892 | if (isKnownViaInduction(Pred, LHS, RHS)) | |||
| 9893 | return true; | |||
| 9894 | ||||
| 9895 | if (isKnownPredicateViaSplitting(Pred, LHS, RHS)) | |||
| 9896 | return true; | |||
| 9897 | ||||
| 9898 | // Otherwise see what can be done with some simple reasoning. | |||
| 9899 | return isKnownViaNonRecursiveReasoning(Pred, LHS, RHS); | |||
| 9900 | } | |||
| 9901 | ||||
| 9902 | Optional<bool> ScalarEvolution::evaluatePredicate(ICmpInst::Predicate Pred, | |||
| 9903 | const SCEV *LHS, | |||
| 9904 | const SCEV *RHS) { | |||
| 9905 | if (isKnownPredicate(Pred, LHS, RHS)) | |||
| 9906 | return true; | |||
| 9907 | else if (isKnownPredicate(ICmpInst::getInversePredicate(Pred), LHS, RHS)) | |||
| 9908 | return false; | |||
| 9909 | return None; | |||
| 9910 | } | |||
| 9911 | ||||
| 9912 | bool ScalarEvolution::isKnownPredicateAt(ICmpInst::Predicate Pred, | |||
| 9913 | const SCEV *LHS, const SCEV *RHS, | |||
| 9914 | const Instruction *Context) { | |||
| 9915 | // TODO: Analyze guards and assumes from Context's block. | |||
| 9916 | return isKnownPredicate(Pred, LHS, RHS) || | |||
| 9917 | isBasicBlockEntryGuardedByCond(Context->getParent(), Pred, LHS, RHS); | |||
| 9918 | } | |||
| 9919 | ||||
| 9920 | Optional<bool> | |||
| 9921 | ScalarEvolution::evaluatePredicateAt(ICmpInst::Predicate Pred, const SCEV *LHS, | |||
| 9922 | const SCEV *RHS, | |||
| 9923 | const Instruction *Context) { | |||
| 9924 | Optional<bool> KnownWithoutContext = evaluatePredicate(Pred, LHS, RHS); | |||
| 9925 | if (KnownWithoutContext) | |||
| 9926 | return KnownWithoutContext; | |||
| 9927 | ||||
| 9928 | if (isBasicBlockEntryGuardedByCond(Context->getParent(), Pred, LHS, RHS)) | |||
| 9929 | return true; | |||
| 9930 | else if (isBasicBlockEntryGuardedByCond(Context->getParent(), | |||
| 9931 | ICmpInst::getInversePredicate(Pred), | |||
| 9932 | LHS, RHS)) | |||
| 9933 | return false; | |||
| 9934 | return None; | |||
| 9935 | } | |||
| 9936 | ||||
| 9937 | bool ScalarEvolution::isKnownOnEveryIteration(ICmpInst::Predicate Pred, | |||
| 9938 | const SCEVAddRecExpr *LHS, | |||
| 9939 | const SCEV *RHS) { | |||
| 9940 | const Loop *L = LHS->getLoop(); | |||
| 9941 | return isLoopEntryGuardedByCond(L, Pred, LHS->getStart(), RHS) && | |||
| 9942 | isLoopBackedgeGuardedByCond(L, Pred, LHS->getPostIncExpr(*this), RHS); | |||
| 9943 | } | |||
| 9944 | ||||
| 9945 | Optional<ScalarEvolution::MonotonicPredicateType> | |||
| 9946 | ScalarEvolution::getMonotonicPredicateType(const SCEVAddRecExpr *LHS, | |||
| 9947 | ICmpInst::Predicate Pred) { | |||
| 9948 | auto Result = getMonotonicPredicateTypeImpl(LHS, Pred); | |||
| 9949 | ||||
| 9950 | #ifndef NDEBUG1 | |||
| 9951 | // Verify an invariant: inverting the predicate should turn a monotonically | |||
| 9952 | // increasing change to a monotonically decreasing one, and vice versa. | |||
| 9953 | if (Result) { | |||
| 9954 | auto ResultSwapped = | |||
| 9955 | getMonotonicPredicateTypeImpl(LHS, ICmpInst::getSwappedPredicate(Pred)); | |||
| 9956 | ||||
| 9957 | assert(ResultSwapped.hasValue() && "should be able to analyze both!")((void)0); | |||
| 9958 | assert(ResultSwapped.getValue() != Result.getValue() &&((void)0) | |||
| 9959 | "monotonicity should flip as we flip the predicate")((void)0); | |||
| 9960 | } | |||
| 9961 | #endif | |||
| 9962 | ||||
| 9963 | return Result; | |||
| 9964 | } | |||
| 9965 | ||||
| 9966 | Optional<ScalarEvolution::MonotonicPredicateType> | |||
| 9967 | ScalarEvolution::getMonotonicPredicateTypeImpl(const SCEVAddRecExpr *LHS, | |||
| 9968 | ICmpInst::Predicate Pred) { | |||
| 9969 | // A zero step value for LHS means the induction variable is essentially a | |||
| 9970 | // loop invariant value. We don't really depend on the predicate actually | |||
| 9971 | // flipping from false to true (for increasing predicates, and the other way | |||
| 9972 | // around for decreasing predicates), all we care about is that *if* the | |||
| 9973 | // predicate changes then it only changes from false to true. | |||
| 9974 | // | |||
| 9975 | // A zero step value in itself is not very useful, but there may be places | |||
| 9976 | // where SCEV can prove X >= 0 but not prove X > 0, so it is helpful to be | |||
| 9977 | // as general as possible. | |||
| 9978 | ||||
| 9979 | // Only handle LE/LT/GE/GT predicates. | |||
| 9980 | if (!ICmpInst::isRelational(Pred)) | |||
| 9981 | return None; | |||
| 9982 | ||||
| 9983 | bool IsGreater = ICmpInst::isGE(Pred) || ICmpInst::isGT(Pred); | |||
| 9984 | assert((IsGreater || ICmpInst::isLE(Pred) || ICmpInst::isLT(Pred)) &&((void)0) | |||
| 9985 | "Should be greater or less!")((void)0); | |||
| 9986 | ||||
| 9987 | // Check that AR does not wrap. | |||
| 9988 | if (ICmpInst::isUnsigned(Pred)) { | |||
| 9989 | if (!LHS->hasNoUnsignedWrap()) | |||
| 9990 | return None; | |||
| 9991 | return IsGreater ? MonotonicallyIncreasing : MonotonicallyDecreasing; | |||
| 9992 | } else { | |||
| 9993 | assert(ICmpInst::isSigned(Pred) &&((void)0) | |||
| 9994 | "Relational predicate is either signed or unsigned!")((void)0); | |||
| 9995 | if (!LHS->hasNoSignedWrap()) | |||
| 9996 | return None; | |||
| 9997 | ||||
| 9998 | const SCEV *Step = LHS->getStepRecurrence(*this); | |||
| 9999 | ||||
| 10000 | if (isKnownNonNegative(Step)) | |||
| 10001 | return IsGreater ? MonotonicallyIncreasing : MonotonicallyDecreasing; | |||
| 10002 | ||||
| 10003 | if (isKnownNonPositive(Step)) | |||
| 10004 | return !IsGreater ? MonotonicallyIncreasing : MonotonicallyDecreasing; | |||
| 10005 | ||||
| 10006 | return None; | |||
| 10007 | } | |||
| 10008 | } | |||
| 10009 | ||||
| 10010 | Optional<ScalarEvolution::LoopInvariantPredicate> | |||
| 10011 | ScalarEvolution::getLoopInvariantPredicate(ICmpInst::Predicate Pred, | |||
| 10012 | const SCEV *LHS, const SCEV *RHS, | |||
| 10013 | const Loop *L) { | |||
| 10014 | ||||
| 10015 | // If there is a loop-invariant, force it into the RHS, otherwise bail out. | |||
| 10016 | if (!isLoopInvariant(RHS, L)) { | |||
| 10017 | if (!isLoopInvariant(LHS, L)) | |||
| 10018 | return None; | |||
| 10019 | ||||
| 10020 | std::swap(LHS, RHS); | |||
| 10021 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 10022 | } | |||
| 10023 | ||||
| 10024 | const SCEVAddRecExpr *ArLHS = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 10025 | if (!ArLHS || ArLHS->getLoop() != L) | |||
| 10026 | return None; | |||
| 10027 | ||||
| 10028 | auto MonotonicType = getMonotonicPredicateType(ArLHS, Pred); | |||
| 10029 | if (!MonotonicType) | |||
| 10030 | return None; | |||
| 10031 | // If the predicate "ArLHS `Pred` RHS" monotonically increases from false to | |||
| 10032 | // true as the loop iterates, and the backedge is control dependent on | |||
| 10033 | // "ArLHS `Pred` RHS" == true then we can reason as follows: | |||
| 10034 | // | |||
| 10035 | // * if the predicate was false in the first iteration then the predicate | |||
| 10036 | // is never evaluated again, since the loop exits without taking the | |||
| 10037 | // backedge. | |||
| 10038 | // * if the predicate was true in the first iteration then it will | |||
| 10039 | // continue to be true for all future iterations since it is | |||
| 10040 | // monotonically increasing. | |||
| 10041 | // | |||
| 10042 | // For both the above possibilities, we can replace the loop varying | |||
| 10043 | // predicate with its value on the first iteration of the loop (which is | |||
| 10044 | // loop invariant). | |||
| 10045 | // | |||
| 10046 | // A similar reasoning applies for a monotonically decreasing predicate, by | |||
| 10047 | // replacing true with false and false with true in the above two bullets. | |||
| 10048 | bool Increasing = *MonotonicType == ScalarEvolution::MonotonicallyIncreasing; | |||
| 10049 | auto P = Increasing ? Pred : ICmpInst::getInversePredicate(Pred); | |||
| 10050 | ||||
| 10051 | if (!isLoopBackedgeGuardedByCond(L, P, LHS, RHS)) | |||
| 10052 | return None; | |||
| 10053 | ||||
| 10054 | return ScalarEvolution::LoopInvariantPredicate(Pred, ArLHS->getStart(), RHS); | |||
| 10055 | } | |||
| 10056 | ||||
| 10057 | Optional<ScalarEvolution::LoopInvariantPredicate> | |||
| 10058 | ScalarEvolution::getLoopInvariantExitCondDuringFirstIterations( | |||
| 10059 | ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, const Loop *L, | |||
| 10060 | const Instruction *Context, const SCEV *MaxIter) { | |||
| 10061 | // Try to prove the following set of facts: | |||
| 10062 | // - The predicate is monotonic in the iteration space. | |||
| 10063 | // - If the check does not fail on the 1st iteration: | |||
| 10064 | // - No overflow will happen during first MaxIter iterations; | |||
| 10065 | // - It will not fail on the MaxIter'th iteration. | |||
| 10066 | // If the check does fail on the 1st iteration, we leave the loop and no | |||
| 10067 | // other checks matter. | |||
| 10068 | ||||
| 10069 | // If there is a loop-invariant, force it into the RHS, otherwise bail out. | |||
| 10070 | if (!isLoopInvariant(RHS, L)) { | |||
| 10071 | if (!isLoopInvariant(LHS, L)) | |||
| 10072 | return None; | |||
| 10073 | ||||
| 10074 | std::swap(LHS, RHS); | |||
| 10075 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 10076 | } | |||
| 10077 | ||||
| 10078 | auto *AR = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 10079 | if (!AR || AR->getLoop() != L) | |||
| 10080 | return None; | |||
| 10081 | ||||
| 10082 | // The predicate must be relational (i.e. <, <=, >=, >). | |||
| 10083 | if (!ICmpInst::isRelational(Pred)) | |||
| 10084 | return None; | |||
| 10085 | ||||
| 10086 | // TODO: Support steps other than +/- 1. | |||
| 10087 | const SCEV *Step = AR->getStepRecurrence(*this); | |||
| 10088 | auto *One = getOne(Step->getType()); | |||
| 10089 | auto *MinusOne = getNegativeSCEV(One); | |||
| 10090 | if (Step != One && Step != MinusOne) | |||
| 10091 | return None; | |||
| 10092 | ||||
| 10093 | // Type mismatch here means that MaxIter is potentially larger than max | |||
| 10094 | // unsigned value in start type, which mean we cannot prove no wrap for the | |||
| 10095 | // indvar. | |||
| 10096 | if (AR->getType() != MaxIter->getType()) | |||
| 10097 | return None; | |||
| 10098 | ||||
| 10099 | // Value of IV on suggested last iteration. | |||
| 10100 | const SCEV *Last = AR->evaluateAtIteration(MaxIter, *this); | |||
| 10101 | // Does it still meet the requirement? | |||
| 10102 | if (!isLoopBackedgeGuardedByCond(L, Pred, Last, RHS)) | |||
| 10103 | return None; | |||
| 10104 | // Because step is +/- 1 and MaxIter has same type as Start (i.e. it does | |||
| 10105 | // not exceed max unsigned value of this type), this effectively proves | |||
| 10106 | // that there is no wrap during the iteration. To prove that there is no | |||
| 10107 | // signed/unsigned wrap, we need to check that | |||
| 10108 | // Start <= Last for step = 1 or Start >= Last for step = -1. | |||
| 10109 | ICmpInst::Predicate NoOverflowPred = | |||
| 10110 | CmpInst::isSigned(Pred) ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; | |||
| 10111 | if (Step == MinusOne) | |||
| 10112 | NoOverflowPred = CmpInst::getSwappedPredicate(NoOverflowPred); | |||
| 10113 | const SCEV *Start = AR->getStart(); | |||
| 10114 | if (!isKnownPredicateAt(NoOverflowPred, Start, Last, Context)) | |||
| 10115 | return None; | |||
| 10116 | ||||
| 10117 | // Everything is fine. | |||
| 10118 | return ScalarEvolution::LoopInvariantPredicate(Pred, Start, RHS); | |||
| 10119 | } | |||
| 10120 | ||||
| 10121 | bool ScalarEvolution::isKnownPredicateViaConstantRanges( | |||
| 10122 | ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) { | |||
| 10123 | if (HasSameValue(LHS, RHS)) | |||
| 10124 | return ICmpInst::isTrueWhenEqual(Pred); | |||
| 10125 | ||||
| 10126 | // This code is split out from isKnownPredicate because it is called from | |||
| 10127 | // within isLoopEntryGuardedByCond. | |||
| 10128 | ||||
| 10129 | auto CheckRanges = [&](const ConstantRange &RangeLHS, | |||
| 10130 | const ConstantRange &RangeRHS) { | |||
| 10131 | return RangeLHS.icmp(Pred, RangeRHS); | |||
| 10132 | }; | |||
| 10133 | ||||
| 10134 | // The check at the top of the function catches the case where the values are | |||
| 10135 | // known to be equal. | |||
| 10136 | if (Pred == CmpInst::ICMP_EQ) | |||
| 10137 | return false; | |||
| 10138 | ||||
| 10139 | if (Pred == CmpInst::ICMP_NE) { | |||
| 10140 | if (CheckRanges(getSignedRange(LHS), getSignedRange(RHS)) || | |||
| 10141 | CheckRanges(getUnsignedRange(LHS), getUnsignedRange(RHS))) | |||
| 10142 | return true; | |||
| 10143 | auto *Diff = getMinusSCEV(LHS, RHS); | |||
| 10144 | return !isa<SCEVCouldNotCompute>(Diff) && isKnownNonZero(Diff); | |||
| 10145 | } | |||
| 10146 | ||||
| 10147 | if (CmpInst::isSigned(Pred)) | |||
| 10148 | return CheckRanges(getSignedRange(LHS), getSignedRange(RHS)); | |||
| 10149 | ||||
| 10150 | return CheckRanges(getUnsignedRange(LHS), getUnsignedRange(RHS)); | |||
| 10151 | } | |||
| 10152 | ||||
| 10153 | bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred, | |||
| 10154 | const SCEV *LHS, | |||
| 10155 | const SCEV *RHS) { | |||
| 10156 | // Match X to (A + C1)<ExpectedFlags> and Y to (A + C2)<ExpectedFlags>, where | |||
| 10157 | // C1 and C2 are constant integers. If either X or Y are not add expressions, | |||
| 10158 | // consider them as X + 0 and Y + 0 respectively. C1 and C2 are returned via | |||
| 10159 | // OutC1 and OutC2. | |||
| 10160 | auto MatchBinaryAddToConst = [this](const SCEV *X, const SCEV *Y, | |||
| 10161 | APInt &OutC1, APInt &OutC2, | |||
| 10162 | SCEV::NoWrapFlags ExpectedFlags) { | |||
| 10163 | const SCEV *XNonConstOp, *XConstOp; | |||
| 10164 | const SCEV *YNonConstOp, *YConstOp; | |||
| 10165 | SCEV::NoWrapFlags XFlagsPresent; | |||
| 10166 | SCEV::NoWrapFlags YFlagsPresent; | |||
| 10167 | ||||
| 10168 | if (!splitBinaryAdd(X, XConstOp, XNonConstOp, XFlagsPresent)) { | |||
| 10169 | XConstOp = getZero(X->getType()); | |||
| 10170 | XNonConstOp = X; | |||
| 10171 | XFlagsPresent = ExpectedFlags; | |||
| 10172 | } | |||
| 10173 | if (!isa<SCEVConstant>(XConstOp) || | |||
| 10174 | (XFlagsPresent & ExpectedFlags) != ExpectedFlags) | |||
| 10175 | return false; | |||
| 10176 | ||||
| 10177 | if (!splitBinaryAdd(Y, YConstOp, YNonConstOp, YFlagsPresent)) { | |||
| 10178 | YConstOp = getZero(Y->getType()); | |||
| 10179 | YNonConstOp = Y; | |||
| 10180 | YFlagsPresent = ExpectedFlags; | |||
| 10181 | } | |||
| 10182 | ||||
| 10183 | if (!isa<SCEVConstant>(YConstOp) || | |||
| 10184 | (YFlagsPresent & ExpectedFlags) != ExpectedFlags) | |||
| 10185 | return false; | |||
| 10186 | ||||
| 10187 | if (YNonConstOp != XNonConstOp) | |||
| 10188 | return false; | |||
| 10189 | ||||
| 10190 | OutC1 = cast<SCEVConstant>(XConstOp)->getAPInt(); | |||
| 10191 | OutC2 = cast<SCEVConstant>(YConstOp)->getAPInt(); | |||
| 10192 | ||||
| 10193 | return true; | |||
| 10194 | }; | |||
| 10195 | ||||
| 10196 | APInt C1; | |||
| 10197 | APInt C2; | |||
| 10198 | ||||
| 10199 | switch (Pred) { | |||
| 10200 | default: | |||
| 10201 | break; | |||
| 10202 | ||||
| 10203 | case ICmpInst::ICMP_SGE: | |||
| 10204 | std::swap(LHS, RHS); | |||
| 10205 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10206 | case ICmpInst::ICMP_SLE: | |||
| 10207 | // (X + C1)<nsw> s<= (X + C2)<nsw> if C1 s<= C2. | |||
| 10208 | if (MatchBinaryAddToConst(LHS, RHS, C1, C2, SCEV::FlagNSW) && C1.sle(C2)) | |||
| 10209 | return true; | |||
| 10210 | ||||
| 10211 | break; | |||
| 10212 | ||||
| 10213 | case ICmpInst::ICMP_SGT: | |||
| 10214 | std::swap(LHS, RHS); | |||
| 10215 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10216 | case ICmpInst::ICMP_SLT: | |||
| 10217 | // (X + C1)<nsw> s< (X + C2)<nsw> if C1 s< C2. | |||
| 10218 | if (MatchBinaryAddToConst(LHS, RHS, C1, C2, SCEV::FlagNSW) && C1.slt(C2)) | |||
| 10219 | return true; | |||
| 10220 | ||||
| 10221 | break; | |||
| 10222 | ||||
| 10223 | case ICmpInst::ICMP_UGE: | |||
| 10224 | std::swap(LHS, RHS); | |||
| 10225 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10226 | case ICmpInst::ICMP_ULE: | |||
| 10227 | // (X + C1)<nuw> u<= (X + C2)<nuw> for C1 u<= C2. | |||
| 10228 | if (MatchBinaryAddToConst(RHS, LHS, C2, C1, SCEV::FlagNUW) && C1.ule(C2)) | |||
| 10229 | return true; | |||
| 10230 | ||||
| 10231 | break; | |||
| 10232 | ||||
| 10233 | case ICmpInst::ICMP_UGT: | |||
| 10234 | std::swap(LHS, RHS); | |||
| 10235 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10236 | case ICmpInst::ICMP_ULT: | |||
| 10237 | // (X + C1)<nuw> u< (X + C2)<nuw> if C1 u< C2. | |||
| 10238 | if (MatchBinaryAddToConst(RHS, LHS, C2, C1, SCEV::FlagNUW) && C1.ult(C2)) | |||
| 10239 | return true; | |||
| 10240 | break; | |||
| 10241 | } | |||
| 10242 | ||||
| 10243 | return false; | |||
| 10244 | } | |||
| 10245 | ||||
| 10246 | bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred, | |||
| 10247 | const SCEV *LHS, | |||
| 10248 | const SCEV *RHS) { | |||
| 10249 | if (Pred != ICmpInst::ICMP_ULT || ProvingSplitPredicate) | |||
| 10250 | return false; | |||
| 10251 | ||||
| 10252 | // Allowing arbitrary number of activations of isKnownPredicateViaSplitting on | |||
| 10253 | // the stack can result in exponential time complexity. | |||
| 10254 | SaveAndRestore<bool> Restore(ProvingSplitPredicate, true); | |||
| 10255 | ||||
| 10256 | // If L >= 0 then I `ult` L <=> I >= 0 && I `slt` L | |||
| 10257 | // | |||
| 10258 | // To prove L >= 0 we use isKnownNonNegative whereas to prove I >= 0 we use | |||
| 10259 | // isKnownPredicate. isKnownPredicate is more powerful, but also more | |||
| 10260 | // expensive; and using isKnownNonNegative(RHS) is sufficient for most of the | |||
| 10261 | // interesting cases seen in practice. We can consider "upgrading" L >= 0 to | |||
| 10262 | // use isKnownPredicate later if needed. | |||
| 10263 | return isKnownNonNegative(RHS) && | |||
| 10264 | isKnownPredicate(CmpInst::ICMP_SGE, LHS, getZero(LHS->getType())) && | |||
| 10265 | isKnownPredicate(CmpInst::ICMP_SLT, LHS, RHS); | |||
| 10266 | } | |||
| 10267 | ||||
| 10268 | bool ScalarEvolution::isImpliedViaGuard(const BasicBlock *BB, | |||
| 10269 | ICmpInst::Predicate Pred, | |||
| 10270 | const SCEV *LHS, const SCEV *RHS) { | |||
| 10271 | // No need to even try if we know the module has no guards. | |||
| 10272 | if (!HasGuards) | |||
| 10273 | return false; | |||
| 10274 | ||||
| 10275 | return any_of(*BB, [&](const Instruction &I) { | |||
| 10276 | using namespace llvm::PatternMatch; | |||
| 10277 | ||||
| 10278 | Value *Condition; | |||
| 10279 | return match(&I, m_Intrinsic<Intrinsic::experimental_guard>( | |||
| 10280 | m_Value(Condition))) && | |||
| 10281 | isImpliedCond(Pred, LHS, RHS, Condition, false); | |||
| 10282 | }); | |||
| 10283 | } | |||
| 10284 | ||||
| 10285 | /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is | |||
| 10286 | /// protected by a conditional between LHS and RHS. This is used to | |||
| 10287 | /// to eliminate casts. | |||
| 10288 | bool | |||
| 10289 | ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L, | |||
| 10290 | ICmpInst::Predicate Pred, | |||
| 10291 | const SCEV *LHS, const SCEV *RHS) { | |||
| 10292 | // Interpret a null as meaning no loop, where there is obviously no guard | |||
| 10293 | // (interprocedural conditions notwithstanding). | |||
| 10294 | if (!L) return true; | |||
| 10295 | ||||
| 10296 | if (VerifyIR) | |||
| 10297 | assert(!verifyFunction(*L->getHeader()->getParent(), &dbgs()) &&((void)0) | |||
| 10298 | "This cannot be done on broken IR!")((void)0); | |||
| 10299 | ||||
| 10300 | ||||
| 10301 | if (isKnownViaNonRecursiveReasoning(Pred, LHS, RHS)) | |||
| 10302 | return true; | |||
| 10303 | ||||
| 10304 | BasicBlock *Latch = L->getLoopLatch(); | |||
| 10305 | if (!Latch) | |||
| 10306 | return false; | |||
| 10307 | ||||
| 10308 | BranchInst *LoopContinuePredicate = | |||
| 10309 | dyn_cast<BranchInst>(Latch->getTerminator()); | |||
| 10310 | if (LoopContinuePredicate && LoopContinuePredicate->isConditional() && | |||
| 10311 | isImpliedCond(Pred, LHS, RHS, | |||
| 10312 | LoopContinuePredicate->getCondition(), | |||
| 10313 | LoopContinuePredicate->getSuccessor(0) != L->getHeader())) | |||
| 10314 | return true; | |||
| 10315 | ||||
| 10316 | // We don't want more than one activation of the following loops on the stack | |||
| 10317 | // -- that can lead to O(n!) time complexity. | |||
| 10318 | if (WalkingBEDominatingConds) | |||
| 10319 | return false; | |||
| 10320 | ||||
| 10321 | SaveAndRestore<bool> ClearOnExit(WalkingBEDominatingConds, true); | |||
| 10322 | ||||
| 10323 | // See if we can exploit a trip count to prove the predicate. | |||
| 10324 | const auto &BETakenInfo = getBackedgeTakenInfo(L); | |||
| 10325 | const SCEV *LatchBECount = BETakenInfo.getExact(Latch, this); | |||
| 10326 | if (LatchBECount != getCouldNotCompute()) { | |||
| 10327 | // We know that Latch branches back to the loop header exactly | |||
| 10328 | // LatchBECount times. This means the backdege condition at Latch is | |||
| 10329 | // equivalent to "{0,+,1} u< LatchBECount". | |||
| 10330 | Type *Ty = LatchBECount->getType(); | |||
| 10331 | auto NoWrapFlags = SCEV::NoWrapFlags(SCEV::FlagNUW | SCEV::FlagNW); | |||
| 10332 | const SCEV *LoopCounter = | |||
| 10333 | getAddRecExpr(getZero(Ty), getOne(Ty), L, NoWrapFlags); | |||
| 10334 | if (isImpliedCond(Pred, LHS, RHS, ICmpInst::ICMP_ULT, LoopCounter, | |||
| 10335 | LatchBECount)) | |||
| 10336 | return true; | |||
| 10337 | } | |||
| 10338 | ||||
| 10339 | // Check conditions due to any @llvm.assume intrinsics. | |||
| 10340 | for (auto &AssumeVH : AC.assumptions()) { | |||
| 10341 | if (!AssumeVH) | |||
| 10342 | continue; | |||
| 10343 | auto *CI = cast<CallInst>(AssumeVH); | |||
| 10344 | if (!DT.dominates(CI, Latch->getTerminator())) | |||
| 10345 | continue; | |||
| 10346 | ||||
| 10347 | if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false)) | |||
| 10348 | return true; | |||
| 10349 | } | |||
| 10350 | ||||
| 10351 | // If the loop is not reachable from the entry block, we risk running into an | |||
| 10352 | // infinite loop as we walk up into the dom tree. These loops do not matter | |||
| 10353 | // anyway, so we just return a conservative answer when we see them. | |||
| 10354 | if (!DT.isReachableFromEntry(L->getHeader())) | |||
| 10355 | return false; | |||
| 10356 | ||||
| 10357 | if (isImpliedViaGuard(Latch, Pred, LHS, RHS)) | |||
| 10358 | return true; | |||
| 10359 | ||||
| 10360 | for (DomTreeNode *DTN = DT[Latch], *HeaderDTN = DT[L->getHeader()]; | |||
| 10361 | DTN != HeaderDTN; DTN = DTN->getIDom()) { | |||
| 10362 | assert(DTN && "should reach the loop header before reaching the root!")((void)0); | |||
| 10363 | ||||
| 10364 | BasicBlock *BB = DTN->getBlock(); | |||
| 10365 | if (isImpliedViaGuard(BB, Pred, LHS, RHS)) | |||
| 10366 | return true; | |||
| 10367 | ||||
| 10368 | BasicBlock *PBB = BB->getSinglePredecessor(); | |||
| 10369 | if (!PBB) | |||
| 10370 | continue; | |||
| 10371 | ||||
| 10372 | BranchInst *ContinuePredicate = dyn_cast<BranchInst>(PBB->getTerminator()); | |||
| 10373 | if (!ContinuePredicate || !ContinuePredicate->isConditional()) | |||
| 10374 | continue; | |||
| 10375 | ||||
| 10376 | Value *Condition = ContinuePredicate->getCondition(); | |||
| 10377 | ||||
| 10378 | // If we have an edge `E` within the loop body that dominates the only | |||
| 10379 | // latch, the condition guarding `E` also guards the backedge. This | |||
| 10380 | // reasoning works only for loops with a single latch. | |||
| 10381 | ||||
| 10382 | BasicBlockEdge DominatingEdge(PBB, BB); | |||
| 10383 | if (DominatingEdge.isSingleEdge()) { | |||
| 10384 | // We're constructively (and conservatively) enumerating edges within the | |||
| 10385 | // loop body that dominate the latch. The dominator tree better agree | |||
| 10386 | // with us on this: | |||
| 10387 | assert(DT.dominates(DominatingEdge, Latch) && "should be!")((void)0); | |||
| 10388 | ||||
| 10389 | if (isImpliedCond(Pred, LHS, RHS, Condition, | |||
| 10390 | BB != ContinuePredicate->getSuccessor(0))) | |||
| 10391 | return true; | |||
| 10392 | } | |||
| 10393 | } | |||
| 10394 | ||||
| 10395 | return false; | |||
| 10396 | } | |||
| 10397 | ||||
| 10398 | bool ScalarEvolution::isBasicBlockEntryGuardedByCond(const BasicBlock *BB, | |||
| 10399 | ICmpInst::Predicate Pred, | |||
| 10400 | const SCEV *LHS, | |||
| 10401 | const SCEV *RHS) { | |||
| 10402 | if (VerifyIR) | |||
| 10403 | assert(!verifyFunction(*BB->getParent(), &dbgs()) &&((void)0) | |||
| 10404 | "This cannot be done on broken IR!")((void)0); | |||
| 10405 | ||||
| 10406 | // If we cannot prove strict comparison (e.g. a > b), maybe we can prove | |||
| 10407 | // the facts (a >= b && a != b) separately. A typical situation is when the | |||
| 10408 | // non-strict comparison is known from ranges and non-equality is known from | |||
| 10409 | // dominating predicates. If we are proving strict comparison, we always try | |||
| 10410 | // to prove non-equality and non-strict comparison separately. | |||
| 10411 | auto NonStrictPredicate = ICmpInst::getNonStrictPredicate(Pred); | |||
| 10412 | const bool ProvingStrictComparison = (Pred != NonStrictPredicate); | |||
| 10413 | bool ProvedNonStrictComparison = false; | |||
| 10414 | bool ProvedNonEquality = false; | |||
| 10415 | ||||
| 10416 | auto SplitAndProve = | |||
| 10417 | [&](std::function<bool(ICmpInst::Predicate)> Fn) -> bool { | |||
| 10418 | if (!ProvedNonStrictComparison) | |||
| 10419 | ProvedNonStrictComparison = Fn(NonStrictPredicate); | |||
| 10420 | if (!ProvedNonEquality) | |||
| 10421 | ProvedNonEquality = Fn(ICmpInst::ICMP_NE); | |||
| 10422 | if (ProvedNonStrictComparison && ProvedNonEquality) | |||
| 10423 | return true; | |||
| 10424 | return false; | |||
| 10425 | }; | |||
| 10426 | ||||
| 10427 | if (ProvingStrictComparison) { | |||
| 10428 | auto ProofFn = [&](ICmpInst::Predicate P) { | |||
| 10429 | return isKnownViaNonRecursiveReasoning(P, LHS, RHS); | |||
| 10430 | }; | |||
| 10431 | if (SplitAndProve(ProofFn)) | |||
| 10432 | return true; | |||
| 10433 | } | |||
| 10434 | ||||
| 10435 | // Try to prove (Pred, LHS, RHS) using isImpliedViaGuard. | |||
| 10436 | auto ProveViaGuard = [&](const BasicBlock *Block) { | |||
| 10437 | if (isImpliedViaGuard(Block, Pred, LHS, RHS)) | |||
| 10438 | return true; | |||
| 10439 | if (ProvingStrictComparison) { | |||
| 10440 | auto ProofFn = [&](ICmpInst::Predicate P) { | |||
| 10441 | return isImpliedViaGuard(Block, P, LHS, RHS); | |||
| 10442 | }; | |||
| 10443 | if (SplitAndProve(ProofFn)) | |||
| 10444 | return true; | |||
| 10445 | } | |||
| 10446 | return false; | |||
| 10447 | }; | |||
| 10448 | ||||
| 10449 | // Try to prove (Pred, LHS, RHS) using isImpliedCond. | |||
| 10450 | auto ProveViaCond = [&](const Value *Condition, bool Inverse) { | |||
| 10451 | const Instruction *Context = &BB->front(); | |||
| 10452 | if (isImpliedCond(Pred, LHS, RHS, Condition, Inverse, Context)) | |||
| 10453 | return true; | |||
| 10454 | if (ProvingStrictComparison) { | |||
| 10455 | auto ProofFn = [&](ICmpInst::Predicate P) { | |||
| 10456 | return isImpliedCond(P, LHS, RHS, Condition, Inverse, Context); | |||
| 10457 | }; | |||
| 10458 | if (SplitAndProve(ProofFn)) | |||
| 10459 | return true; | |||
| 10460 | } | |||
| 10461 | return false; | |||
| 10462 | }; | |||
| 10463 | ||||
| 10464 | // Starting at the block's predecessor, climb up the predecessor chain, as long | |||
| 10465 | // as there are predecessors that can be found that have unique successors | |||
| 10466 | // leading to the original block. | |||
| 10467 | const Loop *ContainingLoop = LI.getLoopFor(BB); | |||
| 10468 | const BasicBlock *PredBB; | |||
| 10469 | if (ContainingLoop && ContainingLoop->getHeader() == BB) | |||
| 10470 | PredBB = ContainingLoop->getLoopPredecessor(); | |||
| 10471 | else | |||
| 10472 | PredBB = BB->getSinglePredecessor(); | |||
| 10473 | for (std::pair<const BasicBlock *, const BasicBlock *> Pair(PredBB, BB); | |||
| 10474 | Pair.first; Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) { | |||
| 10475 | if (ProveViaGuard(Pair.first)) | |||
| 10476 | return true; | |||
| 10477 | ||||
| 10478 | const BranchInst *LoopEntryPredicate = | |||
| 10479 | dyn_cast<BranchInst>(Pair.first->getTerminator()); | |||
| 10480 | if (!LoopEntryPredicate || | |||
| 10481 | LoopEntryPredicate->isUnconditional()) | |||
| 10482 | continue; | |||
| 10483 | ||||
| 10484 | if (ProveViaCond(LoopEntryPredicate->getCondition(), | |||
| 10485 | LoopEntryPredicate->getSuccessor(0) != Pair.second)) | |||
| 10486 | return true; | |||
| 10487 | } | |||
| 10488 | ||||
| 10489 | // Check conditions due to any @llvm.assume intrinsics. | |||
| 10490 | for (auto &AssumeVH : AC.assumptions()) { | |||
| 10491 | if (!AssumeVH) | |||
| 10492 | continue; | |||
| 10493 | auto *CI = cast<CallInst>(AssumeVH); | |||
| 10494 | if (!DT.dominates(CI, BB)) | |||
| 10495 | continue; | |||
| 10496 | ||||
| 10497 | if (ProveViaCond(CI->getArgOperand(0), false)) | |||
| 10498 | return true; | |||
| 10499 | } | |||
| 10500 | ||||
| 10501 | return false; | |||
| 10502 | } | |||
| 10503 | ||||
| 10504 | bool ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L, | |||
| 10505 | ICmpInst::Predicate Pred, | |||
| 10506 | const SCEV *LHS, | |||
| 10507 | const SCEV *RHS) { | |||
| 10508 | // Interpret a null as meaning no loop, where there is obviously no guard | |||
| 10509 | // (interprocedural conditions notwithstanding). | |||
| 10510 | if (!L) | |||
| 10511 | return false; | |||
| 10512 | ||||
| 10513 | // Both LHS and RHS must be available at loop entry. | |||
| 10514 | assert(isAvailableAtLoopEntry(LHS, L) &&((void)0) | |||
| 10515 | "LHS is not available at Loop Entry")((void)0); | |||
| 10516 | assert(isAvailableAtLoopEntry(RHS, L) &&((void)0) | |||
| 10517 | "RHS is not available at Loop Entry")((void)0); | |||
| 10518 | ||||
| 10519 | if (isKnownViaNonRecursiveReasoning(Pred, LHS, RHS)) | |||
| 10520 | return true; | |||
| 10521 | ||||
| 10522 | return isBasicBlockEntryGuardedByCond(L->getHeader(), Pred, LHS, RHS); | |||
| 10523 | } | |||
| 10524 | ||||
| 10525 | bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS, | |||
| 10526 | const SCEV *RHS, | |||
| 10527 | const Value *FoundCondValue, bool Inverse, | |||
| 10528 | const Instruction *Context) { | |||
| 10529 | // False conditions implies anything. Do not bother analyzing it further. | |||
| 10530 | if (FoundCondValue == | |||
| 10531 | ConstantInt::getBool(FoundCondValue->getContext(), Inverse)) | |||
| 10532 | return true; | |||
| 10533 | ||||
| 10534 | if (!PendingLoopPredicates.insert(FoundCondValue).second) | |||
| 10535 | return false; | |||
| 10536 | ||||
| 10537 | auto ClearOnExit = | |||
| 10538 | make_scope_exit([&]() { PendingLoopPredicates.erase(FoundCondValue); }); | |||
| 10539 | ||||
| 10540 | // Recursively handle And and Or conditions. | |||
| 10541 | const Value *Op0, *Op1; | |||
| 10542 | if (match(FoundCondValue, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) { | |||
| 10543 | if (!Inverse) | |||
| 10544 | return isImpliedCond(Pred, LHS, RHS, Op0, Inverse, Context) || | |||
| 10545 | isImpliedCond(Pred, LHS, RHS, Op1, Inverse, Context); | |||
| 10546 | } else if (match(FoundCondValue, m_LogicalOr(m_Value(Op0), m_Value(Op1)))) { | |||
| 10547 | if (Inverse) | |||
| 10548 | return isImpliedCond(Pred, LHS, RHS, Op0, Inverse, Context) || | |||
| 10549 | isImpliedCond(Pred, LHS, RHS, Op1, Inverse, Context); | |||
| 10550 | } | |||
| 10551 | ||||
| 10552 | const ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue); | |||
| 10553 | if (!ICI) return false; | |||
| 10554 | ||||
| 10555 | // Now that we found a conditional branch that dominates the loop or controls | |||
| 10556 | // the loop latch. Check to see if it is the comparison we are looking for. | |||
| 10557 | ICmpInst::Predicate FoundPred; | |||
| 10558 | if (Inverse) | |||
| 10559 | FoundPred = ICI->getInversePredicate(); | |||
| 10560 | else | |||
| 10561 | FoundPred = ICI->getPredicate(); | |||
| 10562 | ||||
| 10563 | const SCEV *FoundLHS = getSCEV(ICI->getOperand(0)); | |||
| 10564 | const SCEV *FoundRHS = getSCEV(ICI->getOperand(1)); | |||
| 10565 | ||||
| 10566 | return isImpliedCond(Pred, LHS, RHS, FoundPred, FoundLHS, FoundRHS, Context); | |||
| 10567 | } | |||
| 10568 | ||||
| 10569 | bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS, | |||
| 10570 | const SCEV *RHS, | |||
| 10571 | ICmpInst::Predicate FoundPred, | |||
| 10572 | const SCEV *FoundLHS, const SCEV *FoundRHS, | |||
| 10573 | const Instruction *Context) { | |||
| 10574 | // Balance the types. | |||
| 10575 | if (getTypeSizeInBits(LHS->getType()) < | |||
| 10576 | getTypeSizeInBits(FoundLHS->getType())) { | |||
| 10577 | // For unsigned and equality predicates, try to prove that both found | |||
| 10578 | // operands fit into narrow unsigned range. If so, try to prove facts in | |||
| 10579 | // narrow types. | |||
| 10580 | if (!CmpInst::isSigned(FoundPred) && !FoundLHS->getType()->isPointerTy()) { | |||
| 10581 | auto *NarrowType = LHS->getType(); | |||
| 10582 | auto *WideType = FoundLHS->getType(); | |||
| 10583 | auto BitWidth = getTypeSizeInBits(NarrowType); | |||
| 10584 | const SCEV *MaxValue = getZeroExtendExpr( | |||
| 10585 | getConstant(APInt::getMaxValue(BitWidth)), WideType); | |||
| 10586 | if (isKnownPredicate(ICmpInst::ICMP_ULE, FoundLHS, MaxValue) && | |||
| 10587 | isKnownPredicate(ICmpInst::ICMP_ULE, FoundRHS, MaxValue)) { | |||
| 10588 | const SCEV *TruncFoundLHS = getTruncateExpr(FoundLHS, NarrowType); | |||
| 10589 | const SCEV *TruncFoundRHS = getTruncateExpr(FoundRHS, NarrowType); | |||
| 10590 | if (isImpliedCondBalancedTypes(Pred, LHS, RHS, FoundPred, TruncFoundLHS, | |||
| 10591 | TruncFoundRHS, Context)) | |||
| 10592 | return true; | |||
| 10593 | } | |||
| 10594 | } | |||
| 10595 | ||||
| 10596 | if (LHS->getType()->isPointerTy()) | |||
| 10597 | return false; | |||
| 10598 | if (CmpInst::isSigned(Pred)) { | |||
| 10599 | LHS = getSignExtendExpr(LHS, FoundLHS->getType()); | |||
| 10600 | RHS = getSignExtendExpr(RHS, FoundLHS->getType()); | |||
| 10601 | } else { | |||
| 10602 | LHS = getZeroExtendExpr(LHS, FoundLHS->getType()); | |||
| 10603 | RHS = getZeroExtendExpr(RHS, FoundLHS->getType()); | |||
| 10604 | } | |||
| 10605 | } else if (getTypeSizeInBits(LHS->getType()) > | |||
| 10606 | getTypeSizeInBits(FoundLHS->getType())) { | |||
| 10607 | if (FoundLHS->getType()->isPointerTy()) | |||
| 10608 | return false; | |||
| 10609 | if (CmpInst::isSigned(FoundPred)) { | |||
| 10610 | FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType()); | |||
| 10611 | FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType()); | |||
| 10612 | } else { | |||
| 10613 | FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType()); | |||
| 10614 | FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType()); | |||
| 10615 | } | |||
| 10616 | } | |||
| 10617 | return isImpliedCondBalancedTypes(Pred, LHS, RHS, FoundPred, FoundLHS, | |||
| 10618 | FoundRHS, Context); | |||
| 10619 | } | |||
| 10620 | ||||
| 10621 | bool ScalarEvolution::isImpliedCondBalancedTypes( | |||
| 10622 | ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, | |||
| 10623 | ICmpInst::Predicate FoundPred, const SCEV *FoundLHS, const SCEV *FoundRHS, | |||
| 10624 | const Instruction *Context) { | |||
| 10625 | assert(getTypeSizeInBits(LHS->getType()) ==((void)0) | |||
| 10626 | getTypeSizeInBits(FoundLHS->getType()) &&((void)0) | |||
| 10627 | "Types should be balanced!")((void)0); | |||
| 10628 | // Canonicalize the query to match the way instcombine will have | |||
| 10629 | // canonicalized the comparison. | |||
| 10630 | if (SimplifyICmpOperands(Pred, LHS, RHS)) | |||
| 10631 | if (LHS == RHS) | |||
| 10632 | return CmpInst::isTrueWhenEqual(Pred); | |||
| 10633 | if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS)) | |||
| 10634 | if (FoundLHS == FoundRHS) | |||
| 10635 | return CmpInst::isFalseWhenEqual(FoundPred); | |||
| 10636 | ||||
| 10637 | // Check to see if we can make the LHS or RHS match. | |||
| 10638 | if (LHS == FoundRHS || RHS == FoundLHS) { | |||
| 10639 | if (isa<SCEVConstant>(RHS)) { | |||
| 10640 | std::swap(FoundLHS, FoundRHS); | |||
| 10641 | FoundPred = ICmpInst::getSwappedPredicate(FoundPred); | |||
| 10642 | } else { | |||
| 10643 | std::swap(LHS, RHS); | |||
| 10644 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 10645 | } | |||
| 10646 | } | |||
| 10647 | ||||
| 10648 | // Check whether the found predicate is the same as the desired predicate. | |||
| 10649 | if (FoundPred == Pred) | |||
| 10650 | return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS, Context); | |||
| 10651 | ||||
| 10652 | // Check whether swapping the found predicate makes it the same as the | |||
| 10653 | // desired predicate. | |||
| 10654 | if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) { | |||
| 10655 | // We can write the implication | |||
| 10656 | // 0. LHS Pred RHS <- FoundLHS SwapPred FoundRHS | |||
| 10657 | // using one of the following ways: | |||
| 10658 | // 1. LHS Pred RHS <- FoundRHS Pred FoundLHS | |||
| 10659 | // 2. RHS SwapPred LHS <- FoundLHS SwapPred FoundRHS | |||
| 10660 | // 3. LHS Pred RHS <- ~FoundLHS Pred ~FoundRHS | |||
| 10661 | // 4. ~LHS SwapPred ~RHS <- FoundLHS SwapPred FoundRHS | |||
| 10662 | // Forms 1. and 2. require swapping the operands of one condition. Don't | |||
| 10663 | // do this if it would break canonical constant/addrec ordering. | |||
| 10664 | if (!isa<SCEVConstant>(RHS) && !isa<SCEVAddRecExpr>(LHS)) | |||
| 10665 | return isImpliedCondOperands(FoundPred, RHS, LHS, FoundLHS, FoundRHS, | |||
| 10666 | Context); | |||
| 10667 | if (!isa<SCEVConstant>(FoundRHS) && !isa<SCEVAddRecExpr>(FoundLHS)) | |||
| 10668 | return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS, Context); | |||
| 10669 | ||||
| 10670 | // Don't try to getNotSCEV pointers. | |||
| 10671 | if (LHS->getType()->isPointerTy() || FoundLHS->getType()->isPointerTy()) | |||
| 10672 | return false; | |||
| 10673 | ||||
| 10674 | // There's no clear preference between forms 3. and 4., try both. | |||
| 10675 | return isImpliedCondOperands(FoundPred, getNotSCEV(LHS), getNotSCEV(RHS), | |||
| 10676 | FoundLHS, FoundRHS, Context) || | |||
| 10677 | isImpliedCondOperands(Pred, LHS, RHS, getNotSCEV(FoundLHS), | |||
| 10678 | getNotSCEV(FoundRHS), Context); | |||
| 10679 | } | |||
| 10680 | ||||
| 10681 | // Unsigned comparison is the same as signed comparison when both the operands | |||
| 10682 | // are non-negative. | |||
| 10683 | if (CmpInst::isUnsigned(FoundPred) && | |||
| 10684 | CmpInst::getSignedPredicate(FoundPred) == Pred && | |||
| 10685 | isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS)) | |||
| 10686 | return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS, Context); | |||
| 10687 | ||||
| 10688 | // Check if we can make progress by sharpening ranges. | |||
| 10689 | if (FoundPred == ICmpInst::ICMP_NE && | |||
| 10690 | (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) { | |||
| 10691 | ||||
| 10692 | const SCEVConstant *C = nullptr; | |||
| 10693 | const SCEV *V = nullptr; | |||
| 10694 | ||||
| 10695 | if (isa<SCEVConstant>(FoundLHS)) { | |||
| 10696 | C = cast<SCEVConstant>(FoundLHS); | |||
| 10697 | V = FoundRHS; | |||
| 10698 | } else { | |||
| 10699 | C = cast<SCEVConstant>(FoundRHS); | |||
| 10700 | V = FoundLHS; | |||
| 10701 | } | |||
| 10702 | ||||
| 10703 | // The guarding predicate tells us that C != V. If the known range | |||
| 10704 | // of V is [C, t), we can sharpen the range to [C + 1, t). The | |||
| 10705 | // range we consider has to correspond to same signedness as the | |||
| 10706 | // predicate we're interested in folding. | |||
| 10707 | ||||
| 10708 | APInt Min = ICmpInst::isSigned(Pred) ? | |||
| 10709 | getSignedRangeMin(V) : getUnsignedRangeMin(V); | |||
| 10710 | ||||
| 10711 | if (Min == C->getAPInt()) { | |||
| 10712 | // Given (V >= Min && V != Min) we conclude V >= (Min + 1). | |||
| 10713 | // This is true even if (Min + 1) wraps around -- in case of | |||
| 10714 | // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)). | |||
| 10715 | ||||
| 10716 | APInt SharperMin = Min + 1; | |||
| 10717 | ||||
| 10718 | switch (Pred) { | |||
| 10719 | case ICmpInst::ICMP_SGE: | |||
| 10720 | case ICmpInst::ICMP_UGE: | |||
| 10721 | // We know V `Pred` SharperMin. If this implies LHS `Pred` | |||
| 10722 | // RHS, we're done. | |||
| 10723 | if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(SharperMin), | |||
| 10724 | Context)) | |||
| 10725 | return true; | |||
| 10726 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10727 | ||||
| 10728 | case ICmpInst::ICMP_SGT: | |||
| 10729 | case ICmpInst::ICMP_UGT: | |||
| 10730 | // We know from the range information that (V `Pred` Min || | |||
| 10731 | // V == Min). We know from the guarding condition that !(V | |||
| 10732 | // == Min). This gives us | |||
| 10733 | // | |||
| 10734 | // V `Pred` Min || V == Min && !(V == Min) | |||
| 10735 | // => V `Pred` Min | |||
| 10736 | // | |||
| 10737 | // If V `Pred` Min implies LHS `Pred` RHS, we're done. | |||
| 10738 | ||||
| 10739 | if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min), | |||
| 10740 | Context)) | |||
| 10741 | return true; | |||
| 10742 | break; | |||
| 10743 | ||||
| 10744 | // `LHS < RHS` and `LHS <= RHS` are handled in the same way as `RHS > LHS` and `RHS >= LHS` respectively. | |||
| 10745 | case ICmpInst::ICMP_SLE: | |||
| 10746 | case ICmpInst::ICMP_ULE: | |||
| 10747 | if (isImpliedCondOperands(CmpInst::getSwappedPredicate(Pred), RHS, | |||
| 10748 | LHS, V, getConstant(SharperMin), Context)) | |||
| 10749 | return true; | |||
| 10750 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 10751 | ||||
| 10752 | case ICmpInst::ICMP_SLT: | |||
| 10753 | case ICmpInst::ICMP_ULT: | |||
| 10754 | if (isImpliedCondOperands(CmpInst::getSwappedPredicate(Pred), RHS, | |||
| 10755 | LHS, V, getConstant(Min), Context)) | |||
| 10756 | return true; | |||
| 10757 | break; | |||
| 10758 | ||||
| 10759 | default: | |||
| 10760 | // No change | |||
| 10761 | break; | |||
| 10762 | } | |||
| 10763 | } | |||
| 10764 | } | |||
| 10765 | ||||
| 10766 | // Check whether the actual condition is beyond sufficient. | |||
| 10767 | if (FoundPred == ICmpInst::ICMP_EQ) | |||
| 10768 | if (ICmpInst::isTrueWhenEqual(Pred)) | |||
| 10769 | if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS, Context)) | |||
| 10770 | return true; | |||
| 10771 | if (Pred == ICmpInst::ICMP_NE) | |||
| 10772 | if (!ICmpInst::isTrueWhenEqual(FoundPred)) | |||
| 10773 | if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS, | |||
| 10774 | Context)) | |||
| 10775 | return true; | |||
| 10776 | ||||
| 10777 | // Otherwise assume the worst. | |||
| 10778 | return false; | |||
| 10779 | } | |||
| 10780 | ||||
| 10781 | bool ScalarEvolution::splitBinaryAdd(const SCEV *Expr, | |||
| 10782 | const SCEV *&L, const SCEV *&R, | |||
| 10783 | SCEV::NoWrapFlags &Flags) { | |||
| 10784 | const auto *AE = dyn_cast<SCEVAddExpr>(Expr); | |||
| 10785 | if (!AE || AE->getNumOperands() != 2) | |||
| 10786 | return false; | |||
| 10787 | ||||
| 10788 | L = AE->getOperand(0); | |||
| 10789 | R = AE->getOperand(1); | |||
| 10790 | Flags = AE->getNoWrapFlags(); | |||
| 10791 | return true; | |||
| 10792 | } | |||
| 10793 | ||||
| 10794 | Optional<APInt> ScalarEvolution::computeConstantDifference(const SCEV *More, | |||
| 10795 | const SCEV *Less) { | |||
| 10796 | // We avoid subtracting expressions here because this function is usually | |||
| 10797 | // fairly deep in the call stack (i.e. is called many times). | |||
| 10798 | ||||
| 10799 | // X - X = 0. | |||
| 10800 | if (More == Less) | |||
| 10801 | return APInt(getTypeSizeInBits(More->getType()), 0); | |||
| 10802 | ||||
| 10803 | if (isa<SCEVAddRecExpr>(Less) && isa<SCEVAddRecExpr>(More)) { | |||
| 10804 | const auto *LAR = cast<SCEVAddRecExpr>(Less); | |||
| 10805 | const auto *MAR = cast<SCEVAddRecExpr>(More); | |||
| 10806 | ||||
| 10807 | if (LAR->getLoop() != MAR->getLoop()) | |||
| 10808 | return None; | |||
| 10809 | ||||
| 10810 | // We look at affine expressions only; not for correctness but to keep | |||
| 10811 | // getStepRecurrence cheap. | |||
| 10812 | if (!LAR->isAffine() || !MAR->isAffine()) | |||
| 10813 | return None; | |||
| 10814 | ||||
| 10815 | if (LAR->getStepRecurrence(*this) != MAR->getStepRecurrence(*this)) | |||
| 10816 | return None; | |||
| 10817 | ||||
| 10818 | Less = LAR->getStart(); | |||
| 10819 | More = MAR->getStart(); | |||
| 10820 | ||||
| 10821 | // fall through | |||
| 10822 | } | |||
| 10823 | ||||
| 10824 | if (isa<SCEVConstant>(Less) && isa<SCEVConstant>(More)) { | |||
| 10825 | const auto &M = cast<SCEVConstant>(More)->getAPInt(); | |||
| 10826 | const auto &L = cast<SCEVConstant>(Less)->getAPInt(); | |||
| 10827 | return M - L; | |||
| 10828 | } | |||
| 10829 | ||||
| 10830 | SCEV::NoWrapFlags Flags; | |||
| 10831 | const SCEV *LLess = nullptr, *RLess = nullptr; | |||
| 10832 | const SCEV *LMore = nullptr, *RMore = nullptr; | |||
| 10833 | const SCEVConstant *C1 = nullptr, *C2 = nullptr; | |||
| 10834 | // Compare (X + C1) vs X. | |||
| 10835 | if (splitBinaryAdd(Less, LLess, RLess, Flags)) | |||
| 10836 | if ((C1 = dyn_cast<SCEVConstant>(LLess))) | |||
| 10837 | if (RLess == More) | |||
| 10838 | return -(C1->getAPInt()); | |||
| 10839 | ||||
| 10840 | // Compare X vs (X + C2). | |||
| 10841 | if (splitBinaryAdd(More, LMore, RMore, Flags)) | |||
| 10842 | if ((C2 = dyn_cast<SCEVConstant>(LMore))) | |||
| 10843 | if (RMore == Less) | |||
| 10844 | return C2->getAPInt(); | |||
| 10845 | ||||
| 10846 | // Compare (X + C1) vs (X + C2). | |||
| 10847 | if (C1 && C2 && RLess == RMore) | |||
| 10848 | return C2->getAPInt() - C1->getAPInt(); | |||
| 10849 | ||||
| 10850 | return None; | |||
| 10851 | } | |||
| 10852 | ||||
| 10853 | bool ScalarEvolution::isImpliedCondOperandsViaAddRecStart( | |||
| 10854 | ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, | |||
| 10855 | const SCEV *FoundLHS, const SCEV *FoundRHS, const Instruction *Context) { | |||
| 10856 | // Try to recognize the following pattern: | |||
| 10857 | // | |||
| 10858 | // FoundRHS = ... | |||
| 10859 | // ... | |||
| 10860 | // loop: | |||
| 10861 | // FoundLHS = {Start,+,W} | |||
| 10862 | // context_bb: // Basic block from the same loop | |||
| 10863 | // known(Pred, FoundLHS, FoundRHS) | |||
| 10864 | // | |||
| 10865 | // If some predicate is known in the context of a loop, it is also known on | |||
| 10866 | // each iteration of this loop, including the first iteration. Therefore, in | |||
| 10867 | // this case, `FoundLHS Pred FoundRHS` implies `Start Pred FoundRHS`. Try to | |||
| 10868 | // prove the original pred using this fact. | |||
| 10869 | if (!Context) | |||
| 10870 | return false; | |||
| 10871 | const BasicBlock *ContextBB = Context->getParent(); | |||
| 10872 | // Make sure AR varies in the context block. | |||
| 10873 | if (auto *AR = dyn_cast<SCEVAddRecExpr>(FoundLHS)) { | |||
| 10874 | const Loop *L = AR->getLoop(); | |||
| 10875 | // Make sure that context belongs to the loop and executes on 1st iteration | |||
| 10876 | // (if it ever executes at all). | |||
| 10877 | if (!L->contains(ContextBB) || !DT.dominates(ContextBB, L->getLoopLatch())) | |||
| 10878 | return false; | |||
| 10879 | if (!isAvailableAtLoopEntry(FoundRHS, AR->getLoop())) | |||
| 10880 | return false; | |||
| 10881 | return isImpliedCondOperands(Pred, LHS, RHS, AR->getStart(), FoundRHS); | |||
| 10882 | } | |||
| 10883 | ||||
| 10884 | if (auto *AR = dyn_cast<SCEVAddRecExpr>(FoundRHS)) { | |||
| 10885 | const Loop *L = AR->getLoop(); | |||
| 10886 | // Make sure that context belongs to the loop and executes on 1st iteration | |||
| 10887 | // (if it ever executes at all). | |||
| 10888 | if (!L->contains(ContextBB) || !DT.dominates(ContextBB, L->getLoopLatch())) | |||
| 10889 | return false; | |||
| 10890 | if (!isAvailableAtLoopEntry(FoundLHS, AR->getLoop())) | |||
| 10891 | return false; | |||
| 10892 | return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, AR->getStart()); | |||
| 10893 | } | |||
| 10894 | ||||
| 10895 | return false; | |||
| 10896 | } | |||
| 10897 | ||||
| 10898 | bool ScalarEvolution::isImpliedCondOperandsViaNoOverflow( | |||
| 10899 | ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, | |||
| 10900 | const SCEV *FoundLHS, const SCEV *FoundRHS) { | |||
| 10901 | if (Pred != CmpInst::ICMP_SLT && Pred != CmpInst::ICMP_ULT) | |||
| 10902 | return false; | |||
| 10903 | ||||
| 10904 | const auto *AddRecLHS = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 10905 | if (!AddRecLHS) | |||
| 10906 | return false; | |||
| 10907 | ||||
| 10908 | const auto *AddRecFoundLHS = dyn_cast<SCEVAddRecExpr>(FoundLHS); | |||
| 10909 | if (!AddRecFoundLHS) | |||
| 10910 | return false; | |||
| 10911 | ||||
| 10912 | // We'd like to let SCEV reason about control dependencies, so we constrain | |||
| 10913 | // both the inequalities to be about add recurrences on the same loop. This | |||
| 10914 | // way we can use isLoopEntryGuardedByCond later. | |||
| 10915 | ||||
| 10916 | const Loop *L = AddRecFoundLHS->getLoop(); | |||
| 10917 | if (L != AddRecLHS->getLoop()) | |||
| 10918 | return false; | |||
| 10919 | ||||
| 10920 | // FoundLHS u< FoundRHS u< -C => (FoundLHS + C) u< (FoundRHS + C) ... (1) | |||
| 10921 | // | |||
| 10922 | // FoundLHS s< FoundRHS s< INT_MIN - C => (FoundLHS + C) s< (FoundRHS + C) | |||
| 10923 | // ... (2) | |||
| 10924 | // | |||
| 10925 | // Informal proof for (2), assuming (1) [*]: | |||
| 10926 | // | |||
| 10927 | // We'll also assume (A s< B) <=> ((A + INT_MIN) u< (B + INT_MIN)) ... (3)[**] | |||
| 10928 | // | |||
| 10929 | // Then | |||
| 10930 | // | |||
| 10931 | // FoundLHS s< FoundRHS s< INT_MIN - C | |||
| 10932 | // <=> (FoundLHS + INT_MIN) u< (FoundRHS + INT_MIN) u< -C [ using (3) ] | |||
| 10933 | // <=> (FoundLHS + INT_MIN + C) u< (FoundRHS + INT_MIN + C) [ using (1) ] | |||
| 10934 | // <=> (FoundLHS + INT_MIN + C + INT_MIN) s< | |||
| 10935 | // (FoundRHS + INT_MIN + C + INT_MIN) [ using (3) ] | |||
| 10936 | // <=> FoundLHS + C s< FoundRHS + C | |||
| 10937 | // | |||
| 10938 | // [*]: (1) can be proved by ruling out overflow. | |||
| 10939 | // | |||
| 10940 | // [**]: This can be proved by analyzing all the four possibilities: | |||
| 10941 | // (A s< 0, B s< 0), (A s< 0, B s>= 0), (A s>= 0, B s< 0) and | |||
| 10942 | // (A s>= 0, B s>= 0). | |||
| 10943 | // | |||
| 10944 | // Note: | |||
| 10945 | // Despite (2), "FoundRHS s< INT_MIN - C" does not mean that "FoundRHS + C" | |||
| 10946 | // will not sign underflow. For instance, say FoundLHS = (i8 -128), FoundRHS | |||
| 10947 | // = (i8 -127) and C = (i8 -100). Then INT_MIN - C = (i8 -28), and FoundRHS | |||
| 10948 | // s< (INT_MIN - C). Lack of sign overflow / underflow in "FoundRHS + C" is | |||
| 10949 | // neither necessary nor sufficient to prove "(FoundLHS + C) s< (FoundRHS + | |||
| 10950 | // C)". | |||
| 10951 | ||||
| 10952 | Optional<APInt> LDiff = computeConstantDifference(LHS, FoundLHS); | |||
| 10953 | Optional<APInt> RDiff = computeConstantDifference(RHS, FoundRHS); | |||
| 10954 | if (!LDiff || !RDiff || *LDiff != *RDiff) | |||
| 10955 | return false; | |||
| 10956 | ||||
| 10957 | if (LDiff->isMinValue()) | |||
| 10958 | return true; | |||
| 10959 | ||||
| 10960 | APInt FoundRHSLimit; | |||
| 10961 | ||||
| 10962 | if (Pred == CmpInst::ICMP_ULT) { | |||
| 10963 | FoundRHSLimit = -(*RDiff); | |||
| 10964 | } else { | |||
| 10965 | assert(Pred == CmpInst::ICMP_SLT && "Checked above!")((void)0); | |||
| 10966 | FoundRHSLimit = APInt::getSignedMinValue(getTypeSizeInBits(RHS->getType())) - *RDiff; | |||
| 10967 | } | |||
| 10968 | ||||
| 10969 | // Try to prove (1) or (2), as needed. | |||
| 10970 | return isAvailableAtLoopEntry(FoundRHS, L) && | |||
| 10971 | isLoopEntryGuardedByCond(L, Pred, FoundRHS, | |||
| 10972 | getConstant(FoundRHSLimit)); | |||
| 10973 | } | |||
| 10974 | ||||
| 10975 | bool ScalarEvolution::isImpliedViaMerge(ICmpInst::Predicate Pred, | |||
| 10976 | const SCEV *LHS, const SCEV *RHS, | |||
| 10977 | const SCEV *FoundLHS, | |||
| 10978 | const SCEV *FoundRHS, unsigned Depth) { | |||
| 10979 | const PHINode *LPhi = nullptr, *RPhi = nullptr; | |||
| 10980 | ||||
| 10981 | auto ClearOnExit = make_scope_exit([&]() { | |||
| 10982 | if (LPhi) { | |||
| 10983 | bool Erased = PendingMerges.erase(LPhi); | |||
| 10984 | assert(Erased && "Failed to erase LPhi!")((void)0); | |||
| 10985 | (void)Erased; | |||
| 10986 | } | |||
| 10987 | if (RPhi) { | |||
| 10988 | bool Erased = PendingMerges.erase(RPhi); | |||
| 10989 | assert(Erased && "Failed to erase RPhi!")((void)0); | |||
| 10990 | (void)Erased; | |||
| 10991 | } | |||
| 10992 | }); | |||
| 10993 | ||||
| 10994 | // Find respective Phis and check that they are not being pending. | |||
| 10995 | if (const SCEVUnknown *LU = dyn_cast<SCEVUnknown>(LHS)) | |||
| 10996 | if (auto *Phi = dyn_cast<PHINode>(LU->getValue())) { | |||
| 10997 | if (!PendingMerges.insert(Phi).second) | |||
| 10998 | return false; | |||
| 10999 | LPhi = Phi; | |||
| 11000 | } | |||
| 11001 | if (const SCEVUnknown *RU = dyn_cast<SCEVUnknown>(RHS)) | |||
| 11002 | if (auto *Phi = dyn_cast<PHINode>(RU->getValue())) { | |||
| 11003 | // If we detect a loop of Phi nodes being processed by this method, for | |||
| 11004 | // example: | |||
| 11005 | // | |||
| 11006 | // %a = phi i32 [ %some1, %preheader ], [ %b, %latch ] | |||
| 11007 | // %b = phi i32 [ %some2, %preheader ], [ %a, %latch ] | |||
| 11008 | // | |||
| 11009 | // we don't want to deal with a case that complex, so return conservative | |||
| 11010 | // answer false. | |||
| 11011 | if (!PendingMerges.insert(Phi).second) | |||
| 11012 | return false; | |||
| 11013 | RPhi = Phi; | |||
| 11014 | } | |||
| 11015 | ||||
| 11016 | // If none of LHS, RHS is a Phi, nothing to do here. | |||
| 11017 | if (!LPhi && !RPhi) | |||
| 11018 | return false; | |||
| 11019 | ||||
| 11020 | // If there is a SCEVUnknown Phi we are interested in, make it left. | |||
| 11021 | if (!LPhi) { | |||
| 11022 | std::swap(LHS, RHS); | |||
| 11023 | std::swap(FoundLHS, FoundRHS); | |||
| 11024 | std::swap(LPhi, RPhi); | |||
| 11025 | Pred = ICmpInst::getSwappedPredicate(Pred); | |||
| 11026 | } | |||
| 11027 | ||||
| 11028 | assert(LPhi && "LPhi should definitely be a SCEVUnknown Phi!")((void)0); | |||
| 11029 | const BasicBlock *LBB = LPhi->getParent(); | |||
| 11030 | const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS); | |||
| 11031 | ||||
| 11032 | auto ProvedEasily = [&](const SCEV *S1, const SCEV *S2) { | |||
| 11033 | return isKnownViaNonRecursiveReasoning(Pred, S1, S2) || | |||
| 11034 | isImpliedCondOperandsViaRanges(Pred, S1, S2, FoundLHS, FoundRHS) || | |||
| 11035 | isImpliedViaOperations(Pred, S1, S2, FoundLHS, FoundRHS, Depth); | |||
| 11036 | }; | |||
| 11037 | ||||
| 11038 | if (RPhi && RPhi->getParent() == LBB) { | |||
| 11039 | // Case one: RHS is also a SCEVUnknown Phi from the same basic block. | |||
| 11040 | // If we compare two Phis from the same block, and for each entry block | |||
| 11041 | // the predicate is true for incoming values from this block, then the | |||
| 11042 | // predicate is also true for the Phis. | |||
| 11043 | for (const BasicBlock *IncBB : predecessors(LBB)) { | |||
| 11044 | const SCEV *L = getSCEV(LPhi->getIncomingValueForBlock(IncBB)); | |||
| 11045 | const SCEV *R = getSCEV(RPhi->getIncomingValueForBlock(IncBB)); | |||
| 11046 | if (!ProvedEasily(L, R)) | |||
| 11047 | return false; | |||
| 11048 | } | |||
| 11049 | } else if (RAR && RAR->getLoop()->getHeader() == LBB) { | |||
| 11050 | // Case two: RHS is also a Phi from the same basic block, and it is an | |||
| 11051 | // AddRec. It means that there is a loop which has both AddRec and Unknown | |||
| 11052 | // PHIs, for it we can compare incoming values of AddRec from above the loop | |||
| 11053 | // and latch with their respective incoming values of LPhi. | |||
| 11054 | // TODO: Generalize to handle loops with many inputs in a header. | |||
| 11055 | if (LPhi->getNumIncomingValues() != 2) return false; | |||
| 11056 | ||||
| 11057 | auto *RLoop = RAR->getLoop(); | |||
| 11058 | auto *Predecessor = RLoop->getLoopPredecessor(); | |||
| 11059 | assert(Predecessor && "Loop with AddRec with no predecessor?")((void)0); | |||
| 11060 | const SCEV *L1 = getSCEV(LPhi->getIncomingValueForBlock(Predecessor)); | |||
| 11061 | if (!ProvedEasily(L1, RAR->getStart())) | |||
| 11062 | return false; | |||
| 11063 | auto *Latch = RLoop->getLoopLatch(); | |||
| 11064 | assert(Latch && "Loop with AddRec with no latch?")((void)0); | |||
| 11065 | const SCEV *L2 = getSCEV(LPhi->getIncomingValueForBlock(Latch)); | |||
| 11066 | if (!ProvedEasily(L2, RAR->getPostIncExpr(*this))) | |||
| 11067 | return false; | |||
| 11068 | } else { | |||
| 11069 | // In all other cases go over inputs of LHS and compare each of them to RHS, | |||
| 11070 | // the predicate is true for (LHS, RHS) if it is true for all such pairs. | |||
| 11071 | // At this point RHS is either a non-Phi, or it is a Phi from some block | |||
| 11072 | // different from LBB. | |||
| 11073 | for (const BasicBlock *IncBB : predecessors(LBB)) { | |||
| 11074 | // Check that RHS is available in this block. | |||
| 11075 | if (!dominates(RHS, IncBB)) | |||
| 11076 | return false; | |||
| 11077 | const SCEV *L = getSCEV(LPhi->getIncomingValueForBlock(IncBB)); | |||
| 11078 | // Make sure L does not refer to a value from a potentially previous | |||
| 11079 | // iteration of a loop. | |||
| 11080 | if (!properlyDominates(L, IncBB)) | |||
| 11081 | return false; | |||
| 11082 | if (!ProvedEasily(L, RHS)) | |||
| 11083 | return false; | |||
| 11084 | } | |||
| 11085 | } | |||
| 11086 | return true; | |||
| 11087 | } | |||
| 11088 | ||||
| 11089 | bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred, | |||
| 11090 | const SCEV *LHS, const SCEV *RHS, | |||
| 11091 | const SCEV *FoundLHS, | |||
| 11092 | const SCEV *FoundRHS, | |||
| 11093 | const Instruction *Context) { | |||
| 11094 | if (isImpliedCondOperandsViaRanges(Pred, LHS, RHS, FoundLHS, FoundRHS)) | |||
| 11095 | return true; | |||
| 11096 | ||||
| 11097 | if (isImpliedCondOperandsViaNoOverflow(Pred, LHS, RHS, FoundLHS, FoundRHS)) | |||
| 11098 | return true; | |||
| 11099 | ||||
| 11100 | if (isImpliedCondOperandsViaAddRecStart(Pred, LHS, RHS, FoundLHS, FoundRHS, | |||
| 11101 | Context)) | |||
| 11102 | return true; | |||
| 11103 | ||||
| 11104 | return isImpliedCondOperandsHelper(Pred, LHS, RHS, | |||
| 11105 | FoundLHS, FoundRHS); | |||
| 11106 | } | |||
| 11107 | ||||
| 11108 | /// Is MaybeMinMaxExpr an (U|S)(Min|Max) of Candidate and some other values? | |||
| 11109 | template <typename MinMaxExprType> | |||
| 11110 | static bool IsMinMaxConsistingOf(const SCEV *MaybeMinMaxExpr, | |||
| 11111 | const SCEV *Candidate) { | |||
| 11112 | const MinMaxExprType *MinMaxExpr = dyn_cast<MinMaxExprType>(MaybeMinMaxExpr); | |||
| 11113 | if (!MinMaxExpr) | |||
| 11114 | return false; | |||
| 11115 | ||||
| 11116 | return is_contained(MinMaxExpr->operands(), Candidate); | |||
| 11117 | } | |||
| 11118 | ||||
| 11119 | static bool IsKnownPredicateViaAddRecStart(ScalarEvolution &SE, | |||
| 11120 | ICmpInst::Predicate Pred, | |||
| 11121 | const SCEV *LHS, const SCEV *RHS) { | |||
| 11122 | // If both sides are affine addrecs for the same loop, with equal | |||
| 11123 | // steps, and we know the recurrences don't wrap, then we only | |||
| 11124 | // need to check the predicate on the starting values. | |||
| 11125 | ||||
| 11126 | if (!ICmpInst::isRelational(Pred)) | |||
| 11127 | return false; | |||
| 11128 | ||||
| 11129 | const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 11130 | if (!LAR) | |||
| 11131 | return false; | |||
| 11132 | const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS); | |||
| 11133 | if (!RAR) | |||
| 11134 | return false; | |||
| 11135 | if (LAR->getLoop() != RAR->getLoop()) | |||
| 11136 | return false; | |||
| 11137 | if (!LAR->isAffine() || !RAR->isAffine()) | |||
| 11138 | return false; | |||
| 11139 | ||||
| 11140 | if (LAR->getStepRecurrence(SE) != RAR->getStepRecurrence(SE)) | |||
| 11141 | return false; | |||
| 11142 | ||||
| 11143 | SCEV::NoWrapFlags NW = ICmpInst::isSigned(Pred) ? | |||
| 11144 | SCEV::FlagNSW : SCEV::FlagNUW; | |||
| 11145 | if (!LAR->getNoWrapFlags(NW) || !RAR->getNoWrapFlags(NW)) | |||
| 11146 | return false; | |||
| 11147 | ||||
| 11148 | return SE.isKnownPredicate(Pred, LAR->getStart(), RAR->getStart()); | |||
| 11149 | } | |||
| 11150 | ||||
| 11151 | /// Is LHS `Pred` RHS true on the virtue of LHS or RHS being a Min or Max | |||
| 11152 | /// expression? | |||
| 11153 | static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE, | |||
| 11154 | ICmpInst::Predicate Pred, | |||
| 11155 | const SCEV *LHS, const SCEV *RHS) { | |||
| 11156 | switch (Pred) { | |||
| 11157 | default: | |||
| 11158 | return false; | |||
| 11159 | ||||
| 11160 | case ICmpInst::ICMP_SGE: | |||
| 11161 | std::swap(LHS, RHS); | |||
| 11162 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 11163 | case ICmpInst::ICMP_SLE: | |||
| 11164 | return | |||
| 11165 | // min(A, ...) <= A | |||
| 11166 | IsMinMaxConsistingOf<SCEVSMinExpr>(LHS, RHS) || | |||
| 11167 | // A <= max(A, ...) | |||
| 11168 | IsMinMaxConsistingOf<SCEVSMaxExpr>(RHS, LHS); | |||
| 11169 | ||||
| 11170 | case ICmpInst::ICMP_UGE: | |||
| 11171 | std::swap(LHS, RHS); | |||
| 11172 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 11173 | case ICmpInst::ICMP_ULE: | |||
| 11174 | return | |||
| 11175 | // min(A, ...) <= A | |||
| 11176 | IsMinMaxConsistingOf<SCEVUMinExpr>(LHS, RHS) || | |||
| 11177 | // A <= max(A, ...) | |||
| 11178 | IsMinMaxConsistingOf<SCEVUMaxExpr>(RHS, LHS); | |||
| 11179 | } | |||
| 11180 | ||||
| 11181 | llvm_unreachable("covered switch fell through?!")__builtin_unreachable(); | |||
| 11182 | } | |||
| 11183 | ||||
| 11184 | bool ScalarEvolution::isImpliedViaOperations(ICmpInst::Predicate Pred, | |||
| 11185 | const SCEV *LHS, const SCEV *RHS, | |||
| 11186 | const SCEV *FoundLHS, | |||
| 11187 | const SCEV *FoundRHS, | |||
| 11188 | unsigned Depth) { | |||
| 11189 | assert(getTypeSizeInBits(LHS->getType()) ==((void)0) | |||
| 11190 | getTypeSizeInBits(RHS->getType()) &&((void)0) | |||
| 11191 | "LHS and RHS have different sizes?")((void)0); | |||
| 11192 | assert(getTypeSizeInBits(FoundLHS->getType()) ==((void)0) | |||
| 11193 | getTypeSizeInBits(FoundRHS->getType()) &&((void)0) | |||
| 11194 | "FoundLHS and FoundRHS have different sizes?")((void)0); | |||
| 11195 | // We want to avoid hurting the compile time with analysis of too big trees. | |||
| 11196 | if (Depth > MaxSCEVOperationsImplicationDepth) | |||
| 11197 | return false; | |||
| 11198 | ||||
| 11199 | // We only want to work with GT comparison so far. | |||
| 11200 | if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT) { | |||
| 11201 | Pred = CmpInst::getSwappedPredicate(Pred); | |||
| 11202 | std::swap(LHS, RHS); | |||
| 11203 | std::swap(FoundLHS, FoundRHS); | |||
| 11204 | } | |||
| 11205 | ||||
| 11206 | // For unsigned, try to reduce it to corresponding signed comparison. | |||
| 11207 | if (Pred == ICmpInst::ICMP_UGT) | |||
| 11208 | // We can replace unsigned predicate with its signed counterpart if all | |||
| 11209 | // involved values are non-negative. | |||
| 11210 | // TODO: We could have better support for unsigned. | |||
| 11211 | if (isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS)) { | |||
| 11212 | // Knowing that both FoundLHS and FoundRHS are non-negative, and knowing | |||
| 11213 | // FoundLHS >u FoundRHS, we also know that FoundLHS >s FoundRHS. Let us | |||
| 11214 | // use this fact to prove that LHS and RHS are non-negative. | |||
| 11215 | const SCEV *MinusOne = getMinusOne(LHS->getType()); | |||
| 11216 | if (isImpliedCondOperands(ICmpInst::ICMP_SGT, LHS, MinusOne, FoundLHS, | |||
| 11217 | FoundRHS) && | |||
| 11218 | isImpliedCondOperands(ICmpInst::ICMP_SGT, RHS, MinusOne, FoundLHS, | |||
| 11219 | FoundRHS)) | |||
| 11220 | Pred = ICmpInst::ICMP_SGT; | |||
| 11221 | } | |||
| 11222 | ||||
| 11223 | if (Pred != ICmpInst::ICMP_SGT) | |||
| 11224 | return false; | |||
| 11225 | ||||
| 11226 | auto GetOpFromSExt = [&](const SCEV *S) { | |||
| 11227 | if (auto *Ext = dyn_cast<SCEVSignExtendExpr>(S)) | |||
| 11228 | return Ext->getOperand(); | |||
| 11229 | // TODO: If S is a SCEVConstant then you can cheaply "strip" the sext off | |||
| 11230 | // the constant in some cases. | |||
| 11231 | return S; | |||
| 11232 | }; | |||
| 11233 | ||||
| 11234 | // Acquire values from extensions. | |||
| 11235 | auto *OrigLHS = LHS; | |||
| 11236 | auto *OrigFoundLHS = FoundLHS; | |||
| 11237 | LHS = GetOpFromSExt(LHS); | |||
| 11238 | FoundLHS = GetOpFromSExt(FoundLHS); | |||
| 11239 | ||||
| 11240 | // Is the SGT predicate can be proved trivially or using the found context. | |||
| 11241 | auto IsSGTViaContext = [&](const SCEV *S1, const SCEV *S2) { | |||
| 11242 | return isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_SGT, S1, S2) || | |||
| 11243 | isImpliedViaOperations(ICmpInst::ICMP_SGT, S1, S2, OrigFoundLHS, | |||
| 11244 | FoundRHS, Depth + 1); | |||
| 11245 | }; | |||
| 11246 | ||||
| 11247 | if (auto *LHSAddExpr = dyn_cast<SCEVAddExpr>(LHS)) { | |||
| 11248 | // We want to avoid creation of any new non-constant SCEV. Since we are | |||
| 11249 | // going to compare the operands to RHS, we should be certain that we don't | |||
| 11250 | // need any size extensions for this. So let's decline all cases when the | |||
| 11251 | // sizes of types of LHS and RHS do not match. | |||
| 11252 | // TODO: Maybe try to get RHS from sext to catch more cases? | |||
| 11253 | if (getTypeSizeInBits(LHS->getType()) != getTypeSizeInBits(RHS->getType())) | |||
| 11254 | return false; | |||
| 11255 | ||||
| 11256 | // Should not overflow. | |||
| 11257 | if (!LHSAddExpr->hasNoSignedWrap()) | |||
| 11258 | return false; | |||
| 11259 | ||||
| 11260 | auto *LL = LHSAddExpr->getOperand(0); | |||
| 11261 | auto *LR = LHSAddExpr->getOperand(1); | |||
| 11262 | auto *MinusOne = getMinusOne(RHS->getType()); | |||
| 11263 | ||||
| 11264 | // Checks that S1 >= 0 && S2 > RHS, trivially or using the found context. | |||
| 11265 | auto IsSumGreaterThanRHS = [&](const SCEV *S1, const SCEV *S2) { | |||
| 11266 | return IsSGTViaContext(S1, MinusOne) && IsSGTViaContext(S2, RHS); | |||
| 11267 | }; | |||
| 11268 | // Try to prove the following rule: | |||
| 11269 | // (LHS = LL + LR) && (LL >= 0) && (LR > RHS) => (LHS > RHS). | |||
| 11270 | // (LHS = LL + LR) && (LR >= 0) && (LL > RHS) => (LHS > RHS). | |||
| 11271 | if (IsSumGreaterThanRHS(LL, LR) || IsSumGreaterThanRHS(LR, LL)) | |||
| 11272 | return true; | |||
| 11273 | } else if (auto *LHSUnknownExpr = dyn_cast<SCEVUnknown>(LHS)) { | |||
| 11274 | Value *LL, *LR; | |||
| 11275 | // FIXME: Once we have SDiv implemented, we can get rid of this matching. | |||
| 11276 | ||||
| 11277 | using namespace llvm::PatternMatch; | |||
| 11278 | ||||
| 11279 | if (match(LHSUnknownExpr->getValue(), m_SDiv(m_Value(LL), m_Value(LR)))) { | |||
| 11280 | // Rules for division. | |||
| 11281 | // We are going to perform some comparisons with Denominator and its | |||
| 11282 | // derivative expressions. In general case, creating a SCEV for it may | |||
| 11283 | // lead to a complex analysis of the entire graph, and in particular it | |||
| 11284 | // can request trip count recalculation for the same loop. This would | |||
| 11285 | // cache as SCEVCouldNotCompute to avoid the infinite recursion. To avoid | |||
| 11286 | // this, we only want to create SCEVs that are constants in this section. | |||
| 11287 | // So we bail if Denominator is not a constant. | |||
| 11288 | if (!isa<ConstantInt>(LR)) | |||
| 11289 | return false; | |||
| 11290 | ||||
| 11291 | auto *Denominator = cast<SCEVConstant>(getSCEV(LR)); | |||
| 11292 | ||||
| 11293 | // We want to make sure that LHS = FoundLHS / Denominator. If it is so, | |||
| 11294 | // then a SCEV for the numerator already exists and matches with FoundLHS. | |||
| 11295 | auto *Numerator = getExistingSCEV(LL); | |||
| 11296 | if (!Numerator || Numerator->getType() != FoundLHS->getType()) | |||
| 11297 | return false; | |||
| 11298 | ||||
| 11299 | // Make sure that the numerator matches with FoundLHS and the denominator | |||
| 11300 | // is positive. | |||
| 11301 | if (!HasSameValue(Numerator, FoundLHS) || !isKnownPositive(Denominator)) | |||
| 11302 | return false; | |||
| 11303 | ||||
| 11304 | auto *DTy = Denominator->getType(); | |||
| 11305 | auto *FRHSTy = FoundRHS->getType(); | |||
| 11306 | if (DTy->isPointerTy() != FRHSTy->isPointerTy()) | |||
| 11307 | // One of types is a pointer and another one is not. We cannot extend | |||
| 11308 | // them properly to a wider type, so let us just reject this case. | |||
| 11309 | // TODO: Usage of getEffectiveSCEVType for DTy, FRHSTy etc should help | |||
| 11310 | // to avoid this check. | |||
| 11311 | return false; | |||
| 11312 | ||||
| 11313 | // Given that: | |||
| 11314 | // FoundLHS > FoundRHS, LHS = FoundLHS / Denominator, Denominator > 0. | |||
| 11315 | auto *WTy = getWiderType(DTy, FRHSTy); | |||
| 11316 | auto *DenominatorExt = getNoopOrSignExtend(Denominator, WTy); | |||
| 11317 | auto *FoundRHSExt = getNoopOrSignExtend(FoundRHS, WTy); | |||
| 11318 | ||||
| 11319 | // Try to prove the following rule: | |||
| 11320 | // (FoundRHS > Denominator - 2) && (RHS <= 0) => (LHS > RHS). | |||
| 11321 | // For example, given that FoundLHS > 2. It means that FoundLHS is at | |||
| 11322 | // least 3. If we divide it by Denominator < 4, we will have at least 1. | |||
| 11323 | auto *DenomMinusTwo = getMinusSCEV(DenominatorExt, getConstant(WTy, 2)); | |||
| 11324 | if (isKnownNonPositive(RHS) && | |||
| 11325 | IsSGTViaContext(FoundRHSExt, DenomMinusTwo)) | |||
| 11326 | return true; | |||
| 11327 | ||||
| 11328 | // Try to prove the following rule: | |||
| 11329 | // (FoundRHS > -1 - Denominator) && (RHS < 0) => (LHS > RHS). | |||
| 11330 | // For example, given that FoundLHS > -3. Then FoundLHS is at least -2. | |||
| 11331 | // If we divide it by Denominator > 2, then: | |||
| 11332 | // 1. If FoundLHS is negative, then the result is 0. | |||
| 11333 | // 2. If FoundLHS is non-negative, then the result is non-negative. | |||
| 11334 | // Anyways, the result is non-negative. | |||
| 11335 | auto *MinusOne = getMinusOne(WTy); | |||
| 11336 | auto *NegDenomMinusOne = getMinusSCEV(MinusOne, DenominatorExt); | |||
| 11337 | if (isKnownNegative(RHS) && | |||
| 11338 | IsSGTViaContext(FoundRHSExt, NegDenomMinusOne)) | |||
| 11339 | return true; | |||
| 11340 | } | |||
| 11341 | } | |||
| 11342 | ||||
| 11343 | // If our expression contained SCEVUnknown Phis, and we split it down and now | |||
| 11344 | // need to prove something for them, try to prove the predicate for every | |||
| 11345 | // possible incoming values of those Phis. | |||
| 11346 | if (isImpliedViaMerge(Pred, OrigLHS, RHS, OrigFoundLHS, FoundRHS, Depth + 1)) | |||
| 11347 | return true; | |||
| 11348 | ||||
| 11349 | return false; | |||
| 11350 | } | |||
| 11351 | ||||
| 11352 | static bool isKnownPredicateExtendIdiom(ICmpInst::Predicate Pred, | |||
| 11353 | const SCEV *LHS, const SCEV *RHS) { | |||
| 11354 | // zext x u<= sext x, sext x s<= zext x | |||
| 11355 | switch (Pred) { | |||
| 11356 | case ICmpInst::ICMP_SGE: | |||
| 11357 | std::swap(LHS, RHS); | |||
| 11358 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 11359 | case ICmpInst::ICMP_SLE: { | |||
| 11360 | // If operand >=s 0 then ZExt == SExt. If operand <s 0 then SExt <s ZExt. | |||
| 11361 | const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(LHS); | |||
| 11362 | const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(RHS); | |||
| 11363 | if (SExt && ZExt && SExt->getOperand() == ZExt->getOperand()) | |||
| 11364 | return true; | |||
| 11365 | break; | |||
| 11366 | } | |||
| 11367 | case ICmpInst::ICMP_UGE: | |||
| 11368 | std::swap(LHS, RHS); | |||
| 11369 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 11370 | case ICmpInst::ICMP_ULE: { | |||
| 11371 | // If operand >=s 0 then ZExt == SExt. If operand <s 0 then ZExt <u SExt. | |||
| 11372 | const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(LHS); | |||
| 11373 | const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(RHS); | |||
| 11374 | if (SExt && ZExt && SExt->getOperand() == ZExt->getOperand()) | |||
| 11375 | return true; | |||
| 11376 | break; | |||
| 11377 | } | |||
| 11378 | default: | |||
| 11379 | break; | |||
| 11380 | }; | |||
| 11381 | return false; | |||
| 11382 | } | |||
| 11383 | ||||
| 11384 | bool | |||
| 11385 | ScalarEvolution::isKnownViaNonRecursiveReasoning(ICmpInst::Predicate Pred, | |||
| 11386 | const SCEV *LHS, const SCEV *RHS) { | |||
| 11387 | return isKnownPredicateExtendIdiom(Pred, LHS, RHS) || | |||
| 11388 | isKnownPredicateViaConstantRanges(Pred, LHS, RHS) || | |||
| 11389 | IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) || | |||
| 11390 | IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) || | |||
| 11391 | isKnownPredicateViaNoOverflow(Pred, LHS, RHS); | |||
| 11392 | } | |||
| 11393 | ||||
| 11394 | bool | |||
| 11395 | ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, | |||
| 11396 | const SCEV *LHS, const SCEV *RHS, | |||
| 11397 | const SCEV *FoundLHS, | |||
| 11398 | const SCEV *FoundRHS) { | |||
| 11399 | switch (Pred) { | |||
| 11400 | default: llvm_unreachable("Unexpected ICmpInst::Predicate value!")__builtin_unreachable(); | |||
| 11401 | case ICmpInst::ICMP_EQ: | |||
| 11402 | case ICmpInst::ICMP_NE: | |||
| 11403 | if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS)) | |||
| 11404 | return true; | |||
| 11405 | break; | |||
| 11406 | case ICmpInst::ICMP_SLT: | |||
| 11407 | case ICmpInst::ICMP_SLE: | |||
| 11408 | if (isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_SLE, LHS, FoundLHS) && | |||
| 11409 | isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_SGE, RHS, FoundRHS)) | |||
| 11410 | return true; | |||
| 11411 | break; | |||
| 11412 | case ICmpInst::ICMP_SGT: | |||
| 11413 | case ICmpInst::ICMP_SGE: | |||
| 11414 | if (isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_SGE, LHS, FoundLHS) && | |||
| 11415 | isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_SLE, RHS, FoundRHS)) | |||
| 11416 | return true; | |||
| 11417 | break; | |||
| 11418 | case ICmpInst::ICMP_ULT: | |||
| 11419 | case ICmpInst::ICMP_ULE: | |||
| 11420 | if (isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_ULE, LHS, FoundLHS) && | |||
| 11421 | isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_UGE, RHS, FoundRHS)) | |||
| 11422 | return true; | |||
| 11423 | break; | |||
| 11424 | case ICmpInst::ICMP_UGT: | |||
| 11425 | case ICmpInst::ICMP_UGE: | |||
| 11426 | if (isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_UGE, LHS, FoundLHS) && | |||
| 11427 | isKnownViaNonRecursiveReasoning(ICmpInst::ICMP_ULE, RHS, FoundRHS)) | |||
| 11428 | return true; | |||
| 11429 | break; | |||
| 11430 | } | |||
| 11431 | ||||
| 11432 | // Maybe it can be proved via operations? | |||
| 11433 | if (isImpliedViaOperations(Pred, LHS, RHS, FoundLHS, FoundRHS)) | |||
| 11434 | return true; | |||
| 11435 | ||||
| 11436 | return false; | |||
| 11437 | } | |||
| 11438 | ||||
| 11439 | bool ScalarEvolution::isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred, | |||
| 11440 | const SCEV *LHS, | |||
| 11441 | const SCEV *RHS, | |||
| 11442 | const SCEV *FoundLHS, | |||
| 11443 | const SCEV *FoundRHS) { | |||
| 11444 | if (!isa<SCEVConstant>(RHS) || !isa<SCEVConstant>(FoundRHS)) | |||
| 11445 | // The restriction on `FoundRHS` be lifted easily -- it exists only to | |||
| 11446 | // reduce the compile time impact of this optimization. | |||
| 11447 | return false; | |||
| 11448 | ||||
| 11449 | Optional<APInt> Addend = computeConstantDifference(LHS, FoundLHS); | |||
| 11450 | if (!Addend) | |||
| 11451 | return false; | |||
| 11452 | ||||
| 11453 | const APInt &ConstFoundRHS = cast<SCEVConstant>(FoundRHS)->getAPInt(); | |||
| 11454 | ||||
| 11455 | // `FoundLHSRange` is the range we know `FoundLHS` to be in by virtue of the | |||
| 11456 | // antecedent "`FoundLHS` `Pred` `FoundRHS`". | |||
| 11457 | ConstantRange FoundLHSRange = | |||
| 11458 | ConstantRange::makeExactICmpRegion(Pred, ConstFoundRHS); | |||
| 11459 | ||||
| 11460 | // Since `LHS` is `FoundLHS` + `Addend`, we can compute a range for `LHS`: | |||
| 11461 | ConstantRange LHSRange = FoundLHSRange.add(ConstantRange(*Addend)); | |||
| 11462 | ||||
| 11463 | // We can also compute the range of values for `LHS` that satisfy the | |||
| 11464 | // consequent, "`LHS` `Pred` `RHS`": | |||
| 11465 | const APInt &ConstRHS = cast<SCEVConstant>(RHS)->getAPInt(); | |||
| 11466 | // The antecedent implies the consequent if every value of `LHS` that | |||
| 11467 | // satisfies the antecedent also satisfies the consequent. | |||
| 11468 | return LHSRange.icmp(Pred, ConstRHS); | |||
| 11469 | } | |||
| 11470 | ||||
| 11471 | bool ScalarEvolution::canIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride, | |||
| 11472 | bool IsSigned) { | |||
| 11473 | assert(isKnownPositive(Stride) && "Positive stride expected!")((void)0); | |||
| 11474 | ||||
| 11475 | unsigned BitWidth = getTypeSizeInBits(RHS->getType()); | |||
| 11476 | const SCEV *One = getOne(Stride->getType()); | |||
| 11477 | ||||
| 11478 | if (IsSigned) { | |||
| 11479 | APInt MaxRHS = getSignedRangeMax(RHS); | |||
| 11480 | APInt MaxValue = APInt::getSignedMaxValue(BitWidth); | |||
| 11481 | APInt MaxStrideMinusOne = getSignedRangeMax(getMinusSCEV(Stride, One)); | |||
| 11482 | ||||
| 11483 | // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow! | |||
| 11484 | return (std::move(MaxValue) - MaxStrideMinusOne).slt(MaxRHS); | |||
| 11485 | } | |||
| 11486 | ||||
| 11487 | APInt MaxRHS = getUnsignedRangeMax(RHS); | |||
| 11488 | APInt MaxValue = APInt::getMaxValue(BitWidth); | |||
| 11489 | APInt MaxStrideMinusOne = getUnsignedRangeMax(getMinusSCEV(Stride, One)); | |||
| 11490 | ||||
| 11491 | // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow! | |||
| 11492 | return (std::move(MaxValue) - MaxStrideMinusOne).ult(MaxRHS); | |||
| 11493 | } | |||
| 11494 | ||||
| 11495 | bool ScalarEvolution::canIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride, | |||
| 11496 | bool IsSigned) { | |||
| 11497 | ||||
| 11498 | unsigned BitWidth = getTypeSizeInBits(RHS->getType()); | |||
| 11499 | const SCEV *One = getOne(Stride->getType()); | |||
| 11500 | ||||
| 11501 | if (IsSigned) { | |||
| 11502 | APInt MinRHS = getSignedRangeMin(RHS); | |||
| 11503 | APInt MinValue = APInt::getSignedMinValue(BitWidth); | |||
| 11504 | APInt MaxStrideMinusOne = getSignedRangeMax(getMinusSCEV(Stride, One)); | |||
| 11505 | ||||
| 11506 | // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow! | |||
| 11507 | return (std::move(MinValue) + MaxStrideMinusOne).sgt(MinRHS); | |||
| 11508 | } | |||
| 11509 | ||||
| 11510 | APInt MinRHS = getUnsignedRangeMin(RHS); | |||
| 11511 | APInt MinValue = APInt::getMinValue(BitWidth); | |||
| 11512 | APInt MaxStrideMinusOne = getUnsignedRangeMax(getMinusSCEV(Stride, One)); | |||
| 11513 | ||||
| 11514 | // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow! | |||
| 11515 | return (std::move(MinValue) + MaxStrideMinusOne).ugt(MinRHS); | |||
| 11516 | } | |||
| 11517 | ||||
| 11518 | const SCEV *ScalarEvolution::getUDivCeilSCEV(const SCEV *N, const SCEV *D) { | |||
| 11519 | // umin(N, 1) + floor((N - umin(N, 1)) / D) | |||
| 11520 | // This is equivalent to "1 + floor((N - 1) / D)" for N != 0. The umin | |||
| 11521 | // expression fixes the case of N=0. | |||
| 11522 | const SCEV *MinNOne = getUMinExpr(N, getOne(N->getType())); | |||
| 11523 | const SCEV *NMinusOne = getMinusSCEV(N, MinNOne); | |||
| 11524 | return getAddExpr(MinNOne, getUDivExpr(NMinusOne, D)); | |||
| 11525 | } | |||
| 11526 | ||||
| 11527 | const SCEV *ScalarEvolution::computeMaxBECountForLT(const SCEV *Start, | |||
| 11528 | const SCEV *Stride, | |||
| 11529 | const SCEV *End, | |||
| 11530 | unsigned BitWidth, | |||
| 11531 | bool IsSigned) { | |||
| 11532 | // The logic in this function assumes we can represent a positive stride. | |||
| 11533 | // If we can't, the backedge-taken count must be zero. | |||
| 11534 | if (IsSigned && BitWidth == 1) | |||
| 11535 | return getZero(Stride->getType()); | |||
| 11536 | ||||
| 11537 | // Calculate the maximum backedge count based on the range of values | |||
| 11538 | // permitted by Start, End, and Stride. | |||
| 11539 | APInt MinStart = | |||
| 11540 | IsSigned ? getSignedRangeMin(Start) : getUnsignedRangeMin(Start); | |||
| 11541 | ||||
| 11542 | APInt MinStride = | |||
| 11543 | IsSigned ? getSignedRangeMin(Stride) : getUnsignedRangeMin(Stride); | |||
| 11544 | ||||
| 11545 | // We assume either the stride is positive, or the backedge-taken count | |||
| 11546 | // is zero. So force StrideForMaxBECount to be at least one. | |||
| 11547 | APInt One(BitWidth, 1); | |||
| 11548 | APInt StrideForMaxBECount = IsSigned ? APIntOps::smax(One, MinStride) | |||
| 11549 | : APIntOps::umax(One, MinStride); | |||
| 11550 | ||||
| 11551 | APInt MaxValue = IsSigned ? APInt::getSignedMaxValue(BitWidth) | |||
| 11552 | : APInt::getMaxValue(BitWidth); | |||
| 11553 | APInt Limit = MaxValue - (StrideForMaxBECount - 1); | |||
| 11554 | ||||
| 11555 | // Although End can be a MAX expression we estimate MaxEnd considering only | |||
| 11556 | // the case End = RHS of the loop termination condition. This is safe because | |||
| 11557 | // in the other case (End - Start) is zero, leading to a zero maximum backedge | |||
| 11558 | // taken count. | |||
| 11559 | APInt MaxEnd = IsSigned ? APIntOps::smin(getSignedRangeMax(End), Limit) | |||
| 11560 | : APIntOps::umin(getUnsignedRangeMax(End), Limit); | |||
| 11561 | ||||
| 11562 | // MaxBECount = ceil((max(MaxEnd, MinStart) - MinStart) / Stride) | |||
| 11563 | MaxEnd = IsSigned ? APIntOps::smax(MaxEnd, MinStart) | |||
| 11564 | : APIntOps::umax(MaxEnd, MinStart); | |||
| 11565 | ||||
| 11566 | return getUDivCeilSCEV(getConstant(MaxEnd - MinStart) /* Delta */, | |||
| 11567 | getConstant(StrideForMaxBECount) /* Step */); | |||
| 11568 | } | |||
| 11569 | ||||
| 11570 | ScalarEvolution::ExitLimit | |||
| 11571 | ScalarEvolution::howManyLessThans(const SCEV *LHS, const SCEV *RHS, | |||
| 11572 | const Loop *L, bool IsSigned, | |||
| 11573 | bool ControlsExit, bool AllowPredicates) { | |||
| 11574 | SmallPtrSet<const SCEVPredicate *, 4> Predicates; | |||
| 11575 | ||||
| 11576 | const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 11577 | bool PredicatedIV = false; | |||
| 11578 | ||||
| 11579 | if (!IV && AllowPredicates) { | |||
| 11580 | // Try to make this an AddRec using runtime tests, in the first X | |||
| 11581 | // iterations of this loop, where X is the SCEV expression found by the | |||
| 11582 | // algorithm below. | |||
| 11583 | IV = convertSCEVToAddRecWithPredicates(LHS, L, Predicates); | |||
| 11584 | PredicatedIV = true; | |||
| 11585 | } | |||
| 11586 | ||||
| 11587 | // Avoid weird loops | |||
| 11588 | if (!IV || IV->getLoop() != L || !IV->isAffine()) | |||
| 11589 | return getCouldNotCompute(); | |||
| 11590 | ||||
| 11591 | // A precondition of this method is that the condition being analyzed | |||
| 11592 | // reaches an exiting branch which dominates the latch. Given that, we can | |||
| 11593 | // assume that an increment which violates the nowrap specification and | |||
| 11594 | // produces poison must cause undefined behavior when the resulting poison | |||
| 11595 | // value is branched upon and thus we can conclude that the backedge is | |||
| 11596 | // taken no more often than would be required to produce that poison value. | |||
| 11597 | // Note that a well defined loop can exit on the iteration which violates | |||
| 11598 | // the nowrap specification if there is another exit (either explicit or | |||
| 11599 | // implicit/exceptional) which causes the loop to execute before the | |||
| 11600 | // exiting instruction we're analyzing would trigger UB. | |||
| 11601 | auto WrapType = IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW; | |||
| 11602 | bool NoWrap = ControlsExit && IV->getNoWrapFlags(WrapType); | |||
| 11603 | ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; | |||
| 11604 | ||||
| 11605 | const SCEV *Stride = IV->getStepRecurrence(*this); | |||
| 11606 | ||||
| 11607 | bool PositiveStride = isKnownPositive(Stride); | |||
| 11608 | ||||
| 11609 | // Avoid negative or zero stride values. | |||
| 11610 | if (!PositiveStride) { | |||
| 11611 | // We can compute the correct backedge taken count for loops with unknown | |||
| 11612 | // strides if we can prove that the loop is not an infinite loop with side | |||
| 11613 | // effects. Here's the loop structure we are trying to handle - | |||
| 11614 | // | |||
| 11615 | // i = start | |||
| 11616 | // do { | |||
| 11617 | // A[i] = i; | |||
| 11618 | // i += s; | |||
| 11619 | // } while (i < end); | |||
| 11620 | // | |||
| 11621 | // The backedge taken count for such loops is evaluated as - | |||
| 11622 | // (max(end, start + stride) - start - 1) /u stride | |||
| 11623 | // | |||
| 11624 | // The additional preconditions that we need to check to prove correctness | |||
| 11625 | // of the above formula is as follows - | |||
| 11626 | // | |||
| 11627 | // a) IV is either nuw or nsw depending upon signedness (indicated by the | |||
| 11628 | // NoWrap flag). | |||
| 11629 | // b) loop is single exit with no side effects. | |||
| 11630 | // | |||
| 11631 | // | |||
| 11632 | // Precondition a) implies that if the stride is negative, this is a single | |||
| 11633 | // trip loop. The backedge taken count formula reduces to zero in this case. | |||
| 11634 | // | |||
| 11635 | // Precondition b) implies that if rhs is invariant in L, then unknown | |||
| 11636 | // stride being zero means the backedge can't be taken without UB. | |||
| 11637 | // | |||
| 11638 | // The positive stride case is the same as isKnownPositive(Stride) returning | |||
| 11639 | // true (original behavior of the function). | |||
| 11640 | // | |||
| 11641 | // We want to make sure that the stride is truly unknown as there are edge | |||
| 11642 | // cases where ScalarEvolution propagates no wrap flags to the | |||
| 11643 | // post-increment/decrement IV even though the increment/decrement operation | |||
| 11644 | // itself is wrapping. The computed backedge taken count may be wrong in | |||
| 11645 | // such cases. This is prevented by checking that the stride is not known to | |||
| 11646 | // be either positive or non-positive. For example, no wrap flags are | |||
| 11647 | // propagated to the post-increment IV of this loop with a trip count of 2 - | |||
| 11648 | // | |||
| 11649 | // unsigned char i; | |||
| 11650 | // for(i=127; i<128; i+=129) | |||
| 11651 | // A[i] = i; | |||
| 11652 | // | |||
| 11653 | if (PredicatedIV || !NoWrap || isKnownNonPositive(Stride) || | |||
| 11654 | !loopIsFiniteByAssumption(L)) | |||
| 11655 | return getCouldNotCompute(); | |||
| 11656 | ||||
| 11657 | if (!isKnownNonZero(Stride)) { | |||
| 11658 | // If we have a step of zero, and RHS isn't invariant in L, we don't know | |||
| 11659 | // if it might eventually be greater than start and if so, on which | |||
| 11660 | // iteration. We can't even produce a useful upper bound. | |||
| 11661 | if (!isLoopInvariant(RHS, L)) | |||
| 11662 | return getCouldNotCompute(); | |||
| 11663 | ||||
| 11664 | // We allow a potentially zero stride, but we need to divide by stride | |||
| 11665 | // below. Since the loop can't be infinite and this check must control | |||
| 11666 | // the sole exit, we can infer the exit must be taken on the first | |||
| 11667 | // iteration (e.g. backedge count = 0) if the stride is zero. Given that, | |||
| 11668 | // we know the numerator in the divides below must be zero, so we can | |||
| 11669 | // pick an arbitrary non-zero value for the denominator (e.g. stride) | |||
| 11670 | // and produce the right result. | |||
| 11671 | // FIXME: Handle the case where Stride is poison? | |||
| 11672 | auto wouldZeroStrideBeUB = [&]() { | |||
| 11673 | // Proof by contradiction. Suppose the stride were zero. If we can | |||
| 11674 | // prove that the backedge *is* taken on the first iteration, then since | |||
| 11675 | // we know this condition controls the sole exit, we must have an | |||
| 11676 | // infinite loop. We can't have a (well defined) infinite loop per | |||
| 11677 | // check just above. | |||
| 11678 | // Note: The (Start - Stride) term is used to get the start' term from | |||
| 11679 | // (start' + stride,+,stride). Remember that we only care about the | |||
| 11680 | // result of this expression when stride == 0 at runtime. | |||
| 11681 | auto *StartIfZero = getMinusSCEV(IV->getStart(), Stride); | |||
| 11682 | return isLoopEntryGuardedByCond(L, Cond, StartIfZero, RHS); | |||
| 11683 | }; | |||
| 11684 | if (!wouldZeroStrideBeUB()) { | |||
| 11685 | Stride = getUMaxExpr(Stride, getOne(Stride->getType())); | |||
| 11686 | } | |||
| 11687 | } | |||
| 11688 | } else if (!Stride->isOne() && !NoWrap) { | |||
| 11689 | auto isUBOnWrap = [&]() { | |||
| 11690 | // Can we prove this loop *must* be UB if overflow of IV occurs? | |||
| 11691 | // Reasoning goes as follows: | |||
| 11692 | // * Suppose the IV did self wrap. | |||
| 11693 | // * If Stride evenly divides the iteration space, then once wrap | |||
| 11694 | // occurs, the loop must revisit the same values. | |||
| 11695 | // * We know that RHS is invariant, and that none of those values | |||
| 11696 | // caused this exit to be taken previously. Thus, this exit is | |||
| 11697 | // dynamically dead. | |||
| 11698 | // * If this is the sole exit, then a dead exit implies the loop | |||
| 11699 | // must be infinite if there are no abnormal exits. | |||
| 11700 | // * If the loop were infinite, then it must either not be mustprogress | |||
| 11701 | // or have side effects. Otherwise, it must be UB. | |||
| 11702 | // * It can't (by assumption), be UB so we have contradicted our | |||
| 11703 | // premise and can conclude the IV did not in fact self-wrap. | |||
| 11704 | // From no-self-wrap, we need to then prove no-(un)signed-wrap. This | |||
| 11705 | // follows trivially from the fact that every (un)signed-wrapped, but | |||
| 11706 | // not self-wrapped value must be LT than the last value before | |||
| 11707 | // (un)signed wrap. Since we know that last value didn't exit, nor | |||
| 11708 | // will any smaller one. | |||
| 11709 | ||||
| 11710 | if (!isLoopInvariant(RHS, L)) | |||
| 11711 | return false; | |||
| 11712 | ||||
| 11713 | auto *StrideC = dyn_cast<SCEVConstant>(Stride); | |||
| 11714 | if (!StrideC || !StrideC->getAPInt().isPowerOf2()) | |||
| 11715 | return false; | |||
| 11716 | ||||
| 11717 | if (!ControlsExit || !loopHasNoAbnormalExits(L)) | |||
| 11718 | return false; | |||
| 11719 | ||||
| 11720 | return loopIsFiniteByAssumption(L); | |||
| 11721 | }; | |||
| 11722 | ||||
| 11723 | // Avoid proven overflow cases: this will ensure that the backedge taken | |||
| 11724 | // count will not generate any unsigned overflow. Relaxed no-overflow | |||
| 11725 | // conditions exploit NoWrapFlags, allowing to optimize in presence of | |||
| 11726 | // undefined behaviors like the case of C language. | |||
| 11727 | if (canIVOverflowOnLT(RHS, Stride, IsSigned) && !isUBOnWrap()) | |||
| 11728 | return getCouldNotCompute(); | |||
| 11729 | } | |||
| 11730 | ||||
| 11731 | // On all paths just preceeding, we established the following invariant: | |||
| 11732 | // IV can be assumed not to overflow up to and including the exiting | |||
| 11733 | // iteration. We proved this in one of two ways: | |||
| 11734 | // 1) We can show overflow doesn't occur before the exiting iteration | |||
| 11735 | // 1a) canIVOverflowOnLT, and b) step of one | |||
| 11736 | // 2) We can show that if overflow occurs, the loop must execute UB | |||
| 11737 | // before any possible exit. | |||
| 11738 | // Note that we have not yet proved RHS invariant (in general). | |||
| 11739 | ||||
| 11740 | const SCEV *Start = IV->getStart(); | |||
| 11741 | ||||
| 11742 | // Preserve pointer-typed Start/RHS to pass to isLoopEntryGuardedByCond. | |||
| 11743 | // Use integer-typed versions for actual computation. | |||
| 11744 | const SCEV *OrigStart = Start; | |||
| 11745 | const SCEV *OrigRHS = RHS; | |||
| 11746 | if (Start->getType()->isPointerTy()) { | |||
| 11747 | Start = getLosslessPtrToIntExpr(Start); | |||
| 11748 | if (isa<SCEVCouldNotCompute>(Start)) | |||
| 11749 | return Start; | |||
| 11750 | } | |||
| 11751 | if (RHS->getType()->isPointerTy()) { | |||
| 11752 | RHS = getLosslessPtrToIntExpr(RHS); | |||
| 11753 | if (isa<SCEVCouldNotCompute>(RHS)) | |||
| 11754 | return RHS; | |||
| 11755 | } | |||
| 11756 | ||||
| 11757 | // When the RHS is not invariant, we do not know the end bound of the loop and | |||
| 11758 | // cannot calculate the ExactBECount needed by ExitLimit. However, we can | |||
| 11759 | // calculate the MaxBECount, given the start, stride and max value for the end | |||
| 11760 | // bound of the loop (RHS), and the fact that IV does not overflow (which is | |||
| 11761 | // checked above). | |||
| 11762 | if (!isLoopInvariant(RHS, L)) { | |||
| 11763 | const SCEV *MaxBECount = computeMaxBECountForLT( | |||
| 11764 | Start, Stride, RHS, getTypeSizeInBits(LHS->getType()), IsSigned); | |||
| 11765 | return ExitLimit(getCouldNotCompute() /* ExactNotTaken */, MaxBECount, | |||
| 11766 | false /*MaxOrZero*/, Predicates); | |||
| 11767 | } | |||
| 11768 | ||||
| 11769 | // We use the expression (max(End,Start)-Start)/Stride to describe the | |||
| 11770 | // backedge count, as if the backedge is taken at least once max(End,Start) | |||
| 11771 | // is End and so the result is as above, and if not max(End,Start) is Start | |||
| 11772 | // so we get a backedge count of zero. | |||
| 11773 | const SCEV *BECount = nullptr; | |||
| 11774 | auto *StartMinusStride = getMinusSCEV(OrigStart, Stride); | |||
| 11775 | // Can we prove (max(RHS,Start) > Start - Stride? | |||
| 11776 | if (isLoopEntryGuardedByCond(L, Cond, StartMinusStride, Start) && | |||
| 11777 | isLoopEntryGuardedByCond(L, Cond, StartMinusStride, RHS)) { | |||
| 11778 | // In this case, we can use a refined formula for computing backedge taken | |||
| 11779 | // count. The general formula remains: | |||
| 11780 | // "End-Start /uceiling Stride" where "End = max(RHS,Start)" | |||
| 11781 | // We want to use the alternate formula: | |||
| 11782 | // "((End - 1) - (Start - Stride)) /u Stride" | |||
| 11783 | // Let's do a quick case analysis to show these are equivalent under | |||
| 11784 | // our precondition that max(RHS,Start) > Start - Stride. | |||
| 11785 | // * For RHS <= Start, the backedge-taken count must be zero. | |||
| 11786 | // "((End - 1) - (Start - Stride)) /u Stride" reduces to | |||
| 11787 | // "((Start - 1) - (Start - Stride)) /u Stride" which simplies to | |||
| 11788 | // "Stride - 1 /u Stride" which is indeed zero for all non-zero values | |||
| 11789 | // of Stride. For 0 stride, we've use umin(1,Stride) above, reducing | |||
| 11790 | // this to the stride of 1 case. | |||
| 11791 | // * For RHS >= Start, the backedge count must be "RHS-Start /uceil Stride". | |||
| 11792 | // "((End - 1) - (Start - Stride)) /u Stride" reduces to | |||
| 11793 | // "((RHS - 1) - (Start - Stride)) /u Stride" reassociates to | |||
| 11794 | // "((RHS - (Start - Stride) - 1) /u Stride". | |||
| 11795 | // Our preconditions trivially imply no overflow in that form. | |||
| 11796 | const SCEV *MinusOne = getMinusOne(Stride->getType()); | |||
| 11797 | const SCEV *Numerator = | |||
| 11798 | getMinusSCEV(getAddExpr(RHS, MinusOne), StartMinusStride); | |||
| 11799 | if (!isa<SCEVCouldNotCompute>(Numerator)) { | |||
| 11800 | BECount = getUDivExpr(Numerator, Stride); | |||
| 11801 | } | |||
| 11802 | } | |||
| 11803 | ||||
| 11804 | const SCEV *BECountIfBackedgeTaken = nullptr; | |||
| 11805 | if (!BECount) { | |||
| 11806 | auto canProveRHSGreaterThanEqualStart = [&]() { | |||
| 11807 | auto CondGE = IsSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; | |||
| 11808 | if (isLoopEntryGuardedByCond(L, CondGE, OrigRHS, OrigStart)) | |||
| 11809 | return true; | |||
| 11810 | ||||
| 11811 | // (RHS > Start - 1) implies RHS >= Start. | |||
| 11812 | // * "RHS >= Start" is trivially equivalent to "RHS > Start - 1" if | |||
| 11813 | // "Start - 1" doesn't overflow. | |||
| 11814 | // * For signed comparison, if Start - 1 does overflow, it's equal | |||
| 11815 | // to INT_MAX, and "RHS >s INT_MAX" is trivially false. | |||
| 11816 | // * For unsigned comparison, if Start - 1 does overflow, it's equal | |||
| 11817 | // to UINT_MAX, and "RHS >u UINT_MAX" is trivially false. | |||
| 11818 | // | |||
| 11819 | // FIXME: Should isLoopEntryGuardedByCond do this for us? | |||
| 11820 | auto CondGT = IsSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; | |||
| 11821 | auto *StartMinusOne = getAddExpr(OrigStart, | |||
| 11822 | getMinusOne(OrigStart->getType())); | |||
| 11823 | return isLoopEntryGuardedByCond(L, CondGT, OrigRHS, StartMinusOne); | |||
| 11824 | }; | |||
| 11825 | ||||
| 11826 | // If we know that RHS >= Start in the context of loop, then we know that | |||
| 11827 | // max(RHS, Start) = RHS at this point. | |||
| 11828 | const SCEV *End; | |||
| 11829 | if (canProveRHSGreaterThanEqualStart()) { | |||
| 11830 | End = RHS; | |||
| 11831 | } else { | |||
| 11832 | // If RHS < Start, the backedge will be taken zero times. So in | |||
| 11833 | // general, we can write the backedge-taken count as: | |||
| 11834 | // | |||
| 11835 | // RHS >= Start ? ceil(RHS - Start) / Stride : 0 | |||
| 11836 | // | |||
| 11837 | // We convert it to the following to make it more convenient for SCEV: | |||
| 11838 | // | |||
| 11839 | // ceil(max(RHS, Start) - Start) / Stride | |||
| 11840 | End = IsSigned ? getSMaxExpr(RHS, Start) : getUMaxExpr(RHS, Start); | |||
| 11841 | ||||
| 11842 | // See what would happen if we assume the backedge is taken. This is | |||
| 11843 | // used to compute MaxBECount. | |||
| 11844 | BECountIfBackedgeTaken = getUDivCeilSCEV(getMinusSCEV(RHS, Start), Stride); | |||
| 11845 | } | |||
| 11846 | ||||
| 11847 | // At this point, we know: | |||
| 11848 | // | |||
| 11849 | // 1. If IsSigned, Start <=s End; otherwise, Start <=u End | |||
| 11850 | // 2. The index variable doesn't overflow. | |||
| 11851 | // | |||
| 11852 | // Therefore, we know N exists such that | |||
| 11853 | // (Start + Stride * N) >= End, and computing "(Start + Stride * N)" | |||
| 11854 | // doesn't overflow. | |||
| 11855 | // | |||
| 11856 | // Using this information, try to prove whether the addition in | |||
| 11857 | // "(Start - End) + (Stride - 1)" has unsigned overflow. | |||
| 11858 | const SCEV *One = getOne(Stride->getType()); | |||
| 11859 | bool MayAddOverflow = [&] { | |||
| 11860 | if (auto *StrideC = dyn_cast<SCEVConstant>(Stride)) { | |||
| 11861 | if (StrideC->getAPInt().isPowerOf2()) { | |||
| 11862 | // Suppose Stride is a power of two, and Start/End are unsigned | |||
| 11863 | // integers. Let UMAX be the largest representable unsigned | |||
| 11864 | // integer. | |||
| 11865 | // | |||
| 11866 | // By the preconditions of this function, we know | |||
| 11867 | // "(Start + Stride * N) >= End", and this doesn't overflow. | |||
| 11868 | // As a formula: | |||
| 11869 | // | |||
| 11870 | // End <= (Start + Stride * N) <= UMAX | |||
| 11871 | // | |||
| 11872 | // Subtracting Start from all the terms: | |||
| 11873 | // | |||
| 11874 | // End - Start <= Stride * N <= UMAX - Start | |||
| 11875 | // | |||
| 11876 | // Since Start is unsigned, UMAX - Start <= UMAX. Therefore: | |||
| 11877 | // | |||
| 11878 | // End - Start <= Stride * N <= UMAX | |||
| 11879 | // | |||
| 11880 | // Stride * N is a multiple of Stride. Therefore, | |||
| 11881 | // | |||
| 11882 | // End - Start <= Stride * N <= UMAX - (UMAX mod Stride) | |||
| 11883 | // | |||
| 11884 | // Since Stride is a power of two, UMAX + 1 is divisible by Stride. | |||
| 11885 | // Therefore, UMAX mod Stride == Stride - 1. So we can write: | |||
| 11886 | // | |||
| 11887 | // End - Start <= Stride * N <= UMAX - Stride - 1 | |||
| 11888 | // | |||
| 11889 | // Dropping the middle term: | |||
| 11890 | // | |||
| 11891 | // End - Start <= UMAX - Stride - 1 | |||
| 11892 | // | |||
| 11893 | // Adding Stride - 1 to both sides: | |||
| 11894 | // | |||
| 11895 | // (End - Start) + (Stride - 1) <= UMAX | |||
| 11896 | // | |||
| 11897 | // In other words, the addition doesn't have unsigned overflow. | |||
| 11898 | // | |||
| 11899 | // A similar proof works if we treat Start/End as signed values. | |||
| 11900 | // Just rewrite steps before "End - Start <= Stride * N <= UMAX" to | |||
| 11901 | // use signed max instead of unsigned max. Note that we're trying | |||
| 11902 | // to prove a lack of unsigned overflow in either case. | |||
| 11903 | return false; | |||
| 11904 | } | |||
| 11905 | } | |||
| 11906 | if (Start == Stride || Start == getMinusSCEV(Stride, One)) { | |||
| 11907 | // If Start is equal to Stride, (End - Start) + (Stride - 1) == End - 1. | |||
| 11908 | // If !IsSigned, 0 <u Stride == Start <=u End; so 0 <u End - 1 <u End. | |||
| 11909 | // If IsSigned, 0 <s Stride == Start <=s End; so 0 <s End - 1 <s End. | |||
| 11910 | // | |||
| 11911 | // If Start is equal to Stride - 1, (End - Start) + Stride - 1 == End. | |||
| 11912 | return false; | |||
| 11913 | } | |||
| 11914 | return true; | |||
| 11915 | }(); | |||
| 11916 | ||||
| 11917 | const SCEV *Delta = getMinusSCEV(End, Start); | |||
| 11918 | if (!MayAddOverflow) { | |||
| 11919 | // floor((D + (S - 1)) / S) | |||
| 11920 | // We prefer this formulation if it's legal because it's fewer operations. | |||
| 11921 | BECount = | |||
| 11922 | getUDivExpr(getAddExpr(Delta, getMinusSCEV(Stride, One)), Stride); | |||
| 11923 | } else { | |||
| 11924 | BECount = getUDivCeilSCEV(Delta, Stride); | |||
| 11925 | } | |||
| 11926 | } | |||
| 11927 | ||||
| 11928 | const SCEV *MaxBECount; | |||
| 11929 | bool MaxOrZero = false; | |||
| 11930 | if (isa<SCEVConstant>(BECount)) { | |||
| 11931 | MaxBECount = BECount; | |||
| 11932 | } else if (BECountIfBackedgeTaken && | |||
| 11933 | isa<SCEVConstant>(BECountIfBackedgeTaken)) { | |||
| 11934 | // If we know exactly how many times the backedge will be taken if it's | |||
| 11935 | // taken at least once, then the backedge count will either be that or | |||
| 11936 | // zero. | |||
| 11937 | MaxBECount = BECountIfBackedgeTaken; | |||
| 11938 | MaxOrZero = true; | |||
| 11939 | } else { | |||
| 11940 | MaxBECount = computeMaxBECountForLT( | |||
| 11941 | Start, Stride, RHS, getTypeSizeInBits(LHS->getType()), IsSigned); | |||
| 11942 | } | |||
| 11943 | ||||
| 11944 | if (isa<SCEVCouldNotCompute>(MaxBECount) && | |||
| 11945 | !isa<SCEVCouldNotCompute>(BECount)) | |||
| 11946 | MaxBECount = getConstant(getUnsignedRangeMax(BECount)); | |||
| 11947 | ||||
| 11948 | return ExitLimit(BECount, MaxBECount, MaxOrZero, Predicates); | |||
| 11949 | } | |||
| 11950 | ||||
| 11951 | ScalarEvolution::ExitLimit | |||
| 11952 | ScalarEvolution::howManyGreaterThans(const SCEV *LHS, const SCEV *RHS, | |||
| 11953 | const Loop *L, bool IsSigned, | |||
| 11954 | bool ControlsExit, bool AllowPredicates) { | |||
| 11955 | SmallPtrSet<const SCEVPredicate *, 4> Predicates; | |||
| 11956 | // We handle only IV > Invariant | |||
| 11957 | if (!isLoopInvariant(RHS, L)) | |||
| 11958 | return getCouldNotCompute(); | |||
| 11959 | ||||
| 11960 | const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS); | |||
| 11961 | if (!IV && AllowPredicates) | |||
| 11962 | // Try to make this an AddRec using runtime tests, in the first X | |||
| 11963 | // iterations of this loop, where X is the SCEV expression found by the | |||
| 11964 | // algorithm below. | |||
| 11965 | IV = convertSCEVToAddRecWithPredicates(LHS, L, Predicates); | |||
| 11966 | ||||
| 11967 | // Avoid weird loops | |||
| 11968 | if (!IV || IV->getLoop() != L || !IV->isAffine()) | |||
| 11969 | return getCouldNotCompute(); | |||
| 11970 | ||||
| 11971 | auto WrapType = IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW; | |||
| 11972 | bool NoWrap = ControlsExit && IV->getNoWrapFlags(WrapType); | |||
| 11973 | ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; | |||
| 11974 | ||||
| 11975 | const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this)); | |||
| 11976 | ||||
| 11977 | // Avoid negative or zero stride values | |||
| 11978 | if (!isKnownPositive(Stride)) | |||
| 11979 | return getCouldNotCompute(); | |||
| 11980 | ||||
| 11981 | // Avoid proven overflow cases: this will ensure that the backedge taken count | |||
| 11982 | // will not generate any unsigned overflow. Relaxed no-overflow conditions | |||
| 11983 | // exploit NoWrapFlags, allowing to optimize in presence of undefined | |||
| 11984 | // behaviors like the case of C language. | |||
| 11985 | if (!Stride->isOne() && !NoWrap) | |||
| 11986 | if (canIVOverflowOnGT(RHS, Stride, IsSigned)) | |||
| 11987 | return getCouldNotCompute(); | |||
| 11988 | ||||
| 11989 | const SCEV *Start = IV->getStart(); | |||
| 11990 | const SCEV *End = RHS; | |||
| 11991 | if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS)) { | |||
| 11992 | // If we know that Start >= RHS in the context of loop, then we know that | |||
| 11993 | // min(RHS, Start) = RHS at this point. | |||
| 11994 | if (isLoopEntryGuardedByCond( | |||
| 11995 | L, IsSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE, Start, RHS)) | |||
| 11996 | End = RHS; | |||
| 11997 | else | |||
| 11998 | End = IsSigned ? getSMinExpr(RHS, Start) : getUMinExpr(RHS, Start); | |||
| 11999 | } | |||
| 12000 | ||||
| 12001 | if (Start->getType()->isPointerTy()) { | |||
| 12002 | Start = getLosslessPtrToIntExpr(Start); | |||
| 12003 | if (isa<SCEVCouldNotCompute>(Start)) | |||
| 12004 | return Start; | |||
| 12005 | } | |||
| 12006 | if (End->getType()->isPointerTy()) { | |||
| 12007 | End = getLosslessPtrToIntExpr(End); | |||
| 12008 | if (isa<SCEVCouldNotCompute>(End)) | |||
| 12009 | return End; | |||
| 12010 | } | |||
| 12011 | ||||
| 12012 | // Compute ((Start - End) + (Stride - 1)) / Stride. | |||
| 12013 | // FIXME: This can overflow. Holding off on fixing this for now; | |||
| 12014 | // howManyGreaterThans will hopefully be gone soon. | |||
| 12015 | const SCEV *One = getOne(Stride->getType()); | |||
| 12016 | const SCEV *BECount = getUDivExpr( | |||
| 12017 | getAddExpr(getMinusSCEV(Start, End), getMinusSCEV(Stride, One)), Stride); | |||
| 12018 | ||||
| 12019 | APInt MaxStart = IsSigned ? getSignedRangeMax(Start) | |||
| 12020 | : getUnsignedRangeMax(Start); | |||
| 12021 | ||||
| 12022 | APInt MinStride = IsSigned ? getSignedRangeMin(Stride) | |||
| 12023 | : getUnsignedRangeMin(Stride); | |||
| 12024 | ||||
| 12025 | unsigned BitWidth = getTypeSizeInBits(LHS->getType()); | |||
| 12026 | APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1) | |||
| 12027 | : APInt::getMinValue(BitWidth) + (MinStride - 1); | |||
| 12028 | ||||
| 12029 | // Although End can be a MIN expression we estimate MinEnd considering only | |||
| 12030 | // the case End = RHS. This is safe because in the other case (Start - End) | |||
| 12031 | // is zero, leading to a zero maximum backedge taken count. | |||
| 12032 | APInt MinEnd = | |||
| 12033 | IsSigned ? APIntOps::smax(getSignedRangeMin(RHS), Limit) | |||
| 12034 | : APIntOps::umax(getUnsignedRangeMin(RHS), Limit); | |||
| 12035 | ||||
| 12036 | const SCEV *MaxBECount = isa<SCEVConstant>(BECount) | |||
| 12037 | ? BECount | |||
| 12038 | : getUDivCeilSCEV(getConstant(MaxStart - MinEnd), | |||
| 12039 | getConstant(MinStride)); | |||
| 12040 | ||||
| 12041 | if (isa<SCEVCouldNotCompute>(MaxBECount)) | |||
| 12042 | MaxBECount = BECount; | |||
| 12043 | ||||
| 12044 | return ExitLimit(BECount, MaxBECount, false, Predicates); | |||
| 12045 | } | |||
| 12046 | ||||
| 12047 | const SCEV *SCEVAddRecExpr::getNumIterationsInRange(const ConstantRange &Range, | |||
| 12048 | ScalarEvolution &SE) const { | |||
| 12049 | if (Range.isFullSet()) // Infinite loop. | |||
| 12050 | return SE.getCouldNotCompute(); | |||
| 12051 | ||||
| 12052 | // If the start is a non-zero constant, shift the range to simplify things. | |||
| 12053 | if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart())) | |||
| 12054 | if (!SC->getValue()->isZero()) { | |||
| 12055 | SmallVector<const SCEV *, 4> Operands(operands()); | |||
| 12056 | Operands[0] = SE.getZero(SC->getType()); | |||
| 12057 | const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(), | |||
| 12058 | getNoWrapFlags(FlagNW)); | |||
| 12059 | if (const auto *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted)) | |||
| 12060 | return ShiftedAddRec->getNumIterationsInRange( | |||
| 12061 | Range.subtract(SC->getAPInt()), SE); | |||
| 12062 | // This is strange and shouldn't happen. | |||
| 12063 | return SE.getCouldNotCompute(); | |||
| 12064 | } | |||
| 12065 | ||||
| 12066 | // The only time we can solve this is when we have all constant indices. | |||
| 12067 | // Otherwise, we cannot determine the overflow conditions. | |||
| 12068 | if (any_of(operands(), [](const SCEV *Op) { return !isa<SCEVConstant>(Op); })) | |||
| 12069 | return SE.getCouldNotCompute(); | |||
| 12070 | ||||
| 12071 | // Okay at this point we know that all elements of the chrec are constants and | |||
| 12072 | // that the start element is zero. | |||
| 12073 | ||||
| 12074 | // First check to see if the range contains zero. If not, the first | |||
| 12075 | // iteration exits. | |||
| 12076 | unsigned BitWidth = SE.getTypeSizeInBits(getType()); | |||
| 12077 | if (!Range.contains(APInt(BitWidth, 0))) | |||
| 12078 | return SE.getZero(getType()); | |||
| 12079 | ||||
| 12080 | if (isAffine()) { | |||
| 12081 | // If this is an affine expression then we have this situation: | |||
| 12082 | // Solve {0,+,A} in Range === Ax in Range | |||
| 12083 | ||||
| 12084 | // We know that zero is in the range. If A is positive then we know that | |||
| 12085 | // the upper value of the range must be the first possible exit value. | |||
| 12086 | // If A is negative then the lower of the range is the last possible loop | |||
| 12087 | // value. Also note that we already checked for a full range. | |||
| 12088 | APInt A = cast<SCEVConstant>(getOperand(1))->getAPInt(); | |||
| 12089 | APInt End = A.sge(1) ? (Range.getUpper() - 1) : Range.getLower(); | |||
| 12090 | ||||
| 12091 | // The exit value should be (End+A)/A. | |||
| 12092 | APInt ExitVal = (End + A).udiv(A); | |||
| 12093 | ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal); | |||
| 12094 | ||||
| 12095 | // Evaluate at the exit value. If we really did fall out of the valid | |||
| 12096 | // range, then we computed our trip count, otherwise wrap around or other | |||
| 12097 | // things must have happened. | |||
| 12098 | ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE); | |||
| 12099 | if (Range.contains(Val->getValue())) | |||
| 12100 | return SE.getCouldNotCompute(); // Something strange happened | |||
| 12101 | ||||
| 12102 | // Ensure that the previous value is in the range. This is a sanity check. | |||
| 12103 | assert(Range.contains(((void)0) | |||
| 12104 | EvaluateConstantChrecAtConstant(this,((void)0) | |||
| 12105 | ConstantInt::get(SE.getContext(), ExitVal - 1), SE)->getValue()) &&((void)0) | |||
| 12106 | "Linear scev computation is off in a bad way!")((void)0); | |||
| 12107 | return SE.getConstant(ExitValue); | |||
| 12108 | } | |||
| 12109 | ||||
| 12110 | if (isQuadratic()) { | |||
| 12111 | if (auto S = SolveQuadraticAddRecRange(this, Range, SE)) | |||
| 12112 | return SE.getConstant(S.getValue()); | |||
| 12113 | } | |||
| 12114 | ||||
| 12115 | return SE.getCouldNotCompute(); | |||
| 12116 | } | |||
| 12117 | ||||
| 12118 | const SCEVAddRecExpr * | |||
| 12119 | SCEVAddRecExpr::getPostIncExpr(ScalarEvolution &SE) const { | |||
| 12120 | assert(getNumOperands() > 1 && "AddRec with zero step?")((void)0); | |||
| 12121 | // There is a temptation to just call getAddExpr(this, getStepRecurrence(SE)), | |||
| 12122 | // but in this case we cannot guarantee that the value returned will be an | |||
| 12123 | // AddRec because SCEV does not have a fixed point where it stops | |||
| 12124 | // simplification: it is legal to return ({rec1} + {rec2}). For example, it | |||
| 12125 | // may happen if we reach arithmetic depth limit while simplifying. So we | |||
| 12126 | // construct the returned value explicitly. | |||
| 12127 | SmallVector<const SCEV *, 3> Ops; | |||
| 12128 | // If this is {A,+,B,+,C,...,+,N}, then its step is {B,+,C,+,...,+,N}, and | |||
| 12129 | // (this + Step) is {A+B,+,B+C,+...,+,N}. | |||
| 12130 | for (unsigned i = 0, e = getNumOperands() - 1; i < e; ++i) | |||
| 12131 | Ops.push_back(SE.getAddExpr(getOperand(i), getOperand(i + 1))); | |||
| 12132 | // We know that the last operand is not a constant zero (otherwise it would | |||
| 12133 | // have been popped out earlier). This guarantees us that if the result has | |||
| 12134 | // the same last operand, then it will also not be popped out, meaning that | |||
| 12135 | // the returned value will be an AddRec. | |||
| 12136 | const SCEV *Last = getOperand(getNumOperands() - 1); | |||
| 12137 | assert(!Last->isZero() && "Recurrency with zero step?")((void)0); | |||
| 12138 | Ops.push_back(Last); | |||
| 12139 | return cast<SCEVAddRecExpr>(SE.getAddRecExpr(Ops, getLoop(), | |||
| 12140 | SCEV::FlagAnyWrap)); | |||
| 12141 | } | |||
| 12142 | ||||
| 12143 | // Return true when S contains at least an undef value. | |||
| 12144 | static inline bool containsUndefs(const SCEV *S) { | |||
| 12145 | return SCEVExprContains(S, [](const SCEV *S) { | |||
| 12146 | if (const auto *SU = dyn_cast<SCEVUnknown>(S)) | |||
| 12147 | return isa<UndefValue>(SU->getValue()); | |||
| 12148 | return false; | |||
| 12149 | }); | |||
| 12150 | } | |||
| 12151 | ||||
| 12152 | namespace { | |||
| 12153 | ||||
| 12154 | // Collect all steps of SCEV expressions. | |||
| 12155 | struct SCEVCollectStrides { | |||
| 12156 | ScalarEvolution &SE; | |||
| 12157 | SmallVectorImpl<const SCEV *> &Strides; | |||
| 12158 | ||||
| 12159 | SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S) | |||
| 12160 | : SE(SE), Strides(S) {} | |||
| 12161 | ||||
| 12162 | bool follow(const SCEV *S) { | |||
| 12163 | if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) | |||
| 12164 | Strides.push_back(AR->getStepRecurrence(SE)); | |||
| 12165 | return true; | |||
| 12166 | } | |||
| 12167 | ||||
| 12168 | bool isDone() const { return false; } | |||
| 12169 | }; | |||
| 12170 | ||||
| 12171 | // Collect all SCEVUnknown and SCEVMulExpr expressions. | |||
| 12172 | struct SCEVCollectTerms { | |||
| 12173 | SmallVectorImpl<const SCEV *> &Terms; | |||
| 12174 | ||||
| 12175 | SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T) : Terms(T) {} | |||
| 12176 | ||||
| 12177 | bool follow(const SCEV *S) { | |||
| 12178 | if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S) || | |||
| 12179 | isa<SCEVSignExtendExpr>(S)) { | |||
| 12180 | if (!containsUndefs(S)) | |||
| 12181 | Terms.push_back(S); | |||
| 12182 | ||||
| 12183 | // Stop recursion: once we collected a term, do not walk its operands. | |||
| 12184 | return false; | |||
| 12185 | } | |||
| 12186 | ||||
| 12187 | // Keep looking. | |||
| 12188 | return true; | |||
| 12189 | } | |||
| 12190 | ||||
| 12191 | bool isDone() const { return false; } | |||
| 12192 | }; | |||
| 12193 | ||||
| 12194 | // Check if a SCEV contains an AddRecExpr. | |||
| 12195 | struct SCEVHasAddRec { | |||
| 12196 | bool &ContainsAddRec; | |||
| 12197 | ||||
| 12198 | SCEVHasAddRec(bool &ContainsAddRec) : ContainsAddRec(ContainsAddRec) { | |||
| 12199 | ContainsAddRec = false; | |||
| 12200 | } | |||
| 12201 | ||||
| 12202 | bool follow(const SCEV *S) { | |||
| 12203 | if (isa<SCEVAddRecExpr>(S)) { | |||
| 12204 | ContainsAddRec = true; | |||
| 12205 | ||||
| 12206 | // Stop recursion: once we collected a term, do not walk its operands. | |||
| 12207 | return false; | |||
| 12208 | } | |||
| 12209 | ||||
| 12210 | // Keep looking. | |||
| 12211 | return true; | |||
| 12212 | } | |||
| 12213 | ||||
| 12214 | bool isDone() const { return false; } | |||
| 12215 | }; | |||
| 12216 | ||||
| 12217 | // Find factors that are multiplied with an expression that (possibly as a | |||
| 12218 | // subexpression) contains an AddRecExpr. In the expression: | |||
| 12219 | // | |||
| 12220 | // 8 * (100 + %p * %q * (%a + {0, +, 1}_loop)) | |||
| 12221 | // | |||
| 12222 | // "%p * %q" are factors multiplied by the expression "(%a + {0, +, 1}_loop)" | |||
| 12223 | // that contains the AddRec {0, +, 1}_loop. %p * %q are likely to be array size | |||
| 12224 | // parameters as they form a product with an induction variable. | |||
| 12225 | // | |||
| 12226 | // This collector expects all array size parameters to be in the same MulExpr. | |||
| 12227 | // It might be necessary to later add support for collecting parameters that are | |||
| 12228 | // spread over different nested MulExpr. | |||
| 12229 | struct SCEVCollectAddRecMultiplies { | |||
| 12230 | SmallVectorImpl<const SCEV *> &Terms; | |||
| 12231 | ScalarEvolution &SE; | |||
| 12232 | ||||
| 12233 | SCEVCollectAddRecMultiplies(SmallVectorImpl<const SCEV *> &T, ScalarEvolution &SE) | |||
| 12234 | : Terms(T), SE(SE) {} | |||
| 12235 | ||||
| 12236 | bool follow(const SCEV *S) { | |||
| 12237 | if (auto *Mul = dyn_cast<SCEVMulExpr>(S)) { | |||
| 12238 | bool HasAddRec = false; | |||
| 12239 | SmallVector<const SCEV *, 0> Operands; | |||
| 12240 | for (auto Op : Mul->operands()) { | |||
| 12241 | const SCEVUnknown *Unknown = dyn_cast<SCEVUnknown>(Op); | |||
| 12242 | if (Unknown && !isa<CallInst>(Unknown->getValue())) { | |||
| 12243 | Operands.push_back(Op); | |||
| 12244 | } else if (Unknown) { | |||
| 12245 | HasAddRec = true; | |||
| 12246 | } else { | |||
| 12247 | bool ContainsAddRec = false; | |||
| 12248 | SCEVHasAddRec ContiansAddRec(ContainsAddRec); | |||
| 12249 | visitAll(Op, ContiansAddRec); | |||
| 12250 | HasAddRec |= ContainsAddRec; | |||
| 12251 | } | |||
| 12252 | } | |||
| 12253 | if (Operands.size() == 0) | |||
| 12254 | return true; | |||
| 12255 | ||||
| 12256 | if (!HasAddRec) | |||
| 12257 | return false; | |||
| 12258 | ||||
| 12259 | Terms.push_back(SE.getMulExpr(Operands)); | |||
| 12260 | // Stop recursion: once we collected a term, do not walk its operands. | |||
| 12261 | return false; | |||
| 12262 | } | |||
| 12263 | ||||
| 12264 | // Keep looking. | |||
| 12265 | return true; | |||
| 12266 | } | |||
| 12267 | ||||
| 12268 | bool isDone() const { return false; } | |||
| 12269 | }; | |||
| 12270 | ||||
| 12271 | } // end anonymous namespace | |||
| 12272 | ||||
| 12273 | /// Find parametric terms in this SCEVAddRecExpr. We first for parameters in | |||
| 12274 | /// two places: | |||
| 12275 | /// 1) The strides of AddRec expressions. | |||
| 12276 | /// 2) Unknowns that are multiplied with AddRec expressions. | |||
| 12277 | void ScalarEvolution::collectParametricTerms(const SCEV *Expr, | |||
| 12278 | SmallVectorImpl<const SCEV *> &Terms) { | |||
| 12279 | SmallVector<const SCEV *, 4> Strides; | |||
| 12280 | SCEVCollectStrides StrideCollector(*this, Strides); | |||
| 12281 | visitAll(Expr, StrideCollector); | |||
| 12282 | ||||
| 12283 | LLVM_DEBUG({do { } while (false) | |||
| 12284 | dbgs() << "Strides:\n";do { } while (false) | |||
| 12285 | for (const SCEV *S : Strides)do { } while (false) | |||
| 12286 | dbgs() << *S << "\n";do { } while (false) | |||
| 12287 | })do { } while (false); | |||
| 12288 | ||||
| 12289 | for (const SCEV *S : Strides) { | |||
| 12290 | SCEVCollectTerms TermCollector(Terms); | |||
| 12291 | visitAll(S, TermCollector); | |||
| 12292 | } | |||
| 12293 | ||||
| 12294 | LLVM_DEBUG({do { } while (false) | |||
| 12295 | dbgs() << "Terms:\n";do { } while (false) | |||
| 12296 | for (const SCEV *T : Terms)do { } while (false) | |||
| 12297 | dbgs() << *T << "\n";do { } while (false) | |||
| 12298 | })do { } while (false); | |||
| 12299 | ||||
| 12300 | SCEVCollectAddRecMultiplies MulCollector(Terms, *this); | |||
| 12301 | visitAll(Expr, MulCollector); | |||
| 12302 | } | |||
| 12303 | ||||
| 12304 | static bool findArrayDimensionsRec(ScalarEvolution &SE, | |||
| 12305 | SmallVectorImpl<const SCEV *> &Terms, | |||
| 12306 | SmallVectorImpl<const SCEV *> &Sizes) { | |||
| 12307 | int Last = Terms.size() - 1; | |||
| 12308 | const SCEV *Step = Terms[Last]; | |||
| 12309 | ||||
| 12310 | // End of recursion. | |||
| 12311 | if (Last == 0) { | |||
| 12312 | if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) { | |||
| 12313 | SmallVector<const SCEV *, 2> Qs; | |||
| 12314 | for (const SCEV *Op : M->operands()) | |||
| 12315 | if (!isa<SCEVConstant>(Op)) | |||
| 12316 | Qs.push_back(Op); | |||
| 12317 | ||||
| 12318 | Step = SE.getMulExpr(Qs); | |||
| 12319 | } | |||
| 12320 | ||||
| 12321 | Sizes.push_back(Step); | |||
| 12322 | return true; | |||
| 12323 | } | |||
| 12324 | ||||
| 12325 | for (const SCEV *&Term : Terms) { | |||
| 12326 | // Normalize the terms before the next call to findArrayDimensionsRec. | |||
| 12327 | const SCEV *Q, *R; | |||
| 12328 | SCEVDivision::divide(SE, Term, Step, &Q, &R); | |||
| 12329 | ||||
| 12330 | // Bail out when GCD does not evenly divide one of the terms. | |||
| 12331 | if (!R->isZero()) | |||
| 12332 | return false; | |||
| 12333 | ||||
| 12334 | Term = Q; | |||
| 12335 | } | |||
| 12336 | ||||
| 12337 | // Remove all SCEVConstants. | |||
| 12338 | erase_if(Terms, [](const SCEV *E) { return isa<SCEVConstant>(E); }); | |||
| 12339 | ||||
| 12340 | if (Terms.size() > 0) | |||
| 12341 | if (!findArrayDimensionsRec(SE, Terms, Sizes)) | |||
| 12342 | return false; | |||
| 12343 | ||||
| 12344 | Sizes.push_back(Step); | |||
| 12345 | return true; | |||
| 12346 | } | |||
| 12347 | ||||
| 12348 | // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter. | |||
| 12349 | static inline bool containsParameters(SmallVectorImpl<const SCEV *> &Terms) { | |||
| 12350 | for (const SCEV *T : Terms) | |||
| 12351 | if (SCEVExprContains(T, [](const SCEV *S) { return isa<SCEVUnknown>(S); })) | |||
| 12352 | return true; | |||
| 12353 | ||||
| 12354 | return false; | |||
| 12355 | } | |||
| 12356 | ||||
| 12357 | // Return the number of product terms in S. | |||
| 12358 | static inline int numberOfTerms(const SCEV *S) { | |||
| 12359 | if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S)) | |||
| 12360 | return Expr->getNumOperands(); | |||
| 12361 | return 1; | |||
| 12362 | } | |||
| 12363 | ||||
| 12364 | static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) { | |||
| 12365 | if (isa<SCEVConstant>(T)) | |||
| 12366 | return nullptr; | |||
| 12367 | ||||
| 12368 | if (isa<SCEVUnknown>(T)) | |||
| 12369 | return T; | |||
| 12370 | ||||
| 12371 | if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) { | |||
| 12372 | SmallVector<const SCEV *, 2> Factors; | |||
| 12373 | for (const SCEV *Op : M->operands()) | |||
| 12374 | if (!isa<SCEVConstant>(Op)) | |||
| 12375 | Factors.push_back(Op); | |||
| 12376 | ||||
| 12377 | return SE.getMulExpr(Factors); | |||
| 12378 | } | |||
| 12379 | ||||
| 12380 | return T; | |||
| 12381 | } | |||
| 12382 | ||||
| 12383 | /// Return the size of an element read or written by Inst. | |||
| 12384 | const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) { | |||
| 12385 | Type *Ty; | |||
| 12386 | if (StoreInst *Store = dyn_cast<StoreInst>(Inst)) | |||
| 12387 | Ty = Store->getValueOperand()->getType(); | |||
| 12388 | else if (LoadInst *Load = dyn_cast<LoadInst>(Inst)) | |||
| 12389 | Ty = Load->getType(); | |||
| 12390 | else | |||
| 12391 | return nullptr; | |||
| 12392 | ||||
| 12393 | Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty)); | |||
| 12394 | return getSizeOfExpr(ETy, Ty); | |||
| 12395 | } | |||
| 12396 | ||||
| 12397 | void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms, | |||
| 12398 | SmallVectorImpl<const SCEV *> &Sizes, | |||
| 12399 | const SCEV *ElementSize) { | |||
| 12400 | if (Terms.size() < 1 || !ElementSize) | |||
| 12401 | return; | |||
| 12402 | ||||
| 12403 | // Early return when Terms do not contain parameters: we do not delinearize | |||
| 12404 | // non parametric SCEVs. | |||
| 12405 | if (!containsParameters(Terms)) | |||
| 12406 | return; | |||
| 12407 | ||||
| 12408 | LLVM_DEBUG({do { } while (false) | |||
| 12409 | dbgs() << "Terms:\n";do { } while (false) | |||
| 12410 | for (const SCEV *T : Terms)do { } while (false) | |||
| 12411 | dbgs() << *T << "\n";do { } while (false) | |||
| 12412 | })do { } while (false); | |||
| 12413 | ||||
| 12414 | // Remove duplicates. | |||
| 12415 | array_pod_sort(Terms.begin(), Terms.end()); | |||
| 12416 | Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end()); | |||
| 12417 | ||||
| 12418 | // Put larger terms first. | |||
| 12419 | llvm::sort(Terms, [](const SCEV *LHS, const SCEV *RHS) { | |||
| 12420 | return numberOfTerms(LHS) > numberOfTerms(RHS); | |||
| 12421 | }); | |||
| 12422 | ||||
| 12423 | // Try to divide all terms by the element size. If term is not divisible by | |||
| 12424 | // element size, proceed with the original term. | |||
| 12425 | for (const SCEV *&Term : Terms) { | |||
| 12426 | const SCEV *Q, *R; | |||
| 12427 | SCEVDivision::divide(*this, Term, ElementSize, &Q, &R); | |||
| 12428 | if (!Q->isZero()) | |||
| 12429 | Term = Q; | |||
| 12430 | } | |||
| 12431 | ||||
| 12432 | SmallVector<const SCEV *, 4> NewTerms; | |||
| 12433 | ||||
| 12434 | // Remove constant factors. | |||
| 12435 | for (const SCEV *T : Terms) | |||
| 12436 | if (const SCEV *NewT = removeConstantFactors(*this, T)) | |||
| 12437 | NewTerms.push_back(NewT); | |||
| 12438 | ||||
| 12439 | LLVM_DEBUG({do { } while (false) | |||
| 12440 | dbgs() << "Terms after sorting:\n";do { } while (false) | |||
| 12441 | for (const SCEV *T : NewTerms)do { } while (false) | |||
| 12442 | dbgs() << *T << "\n";do { } while (false) | |||
| 12443 | })do { } while (false); | |||
| 12444 | ||||
| 12445 | if (NewTerms.empty() || !findArrayDimensionsRec(*this, NewTerms, Sizes)) { | |||
| 12446 | Sizes.clear(); | |||
| 12447 | return; | |||
| 12448 | } | |||
| 12449 | ||||
| 12450 | // The last element to be pushed into Sizes is the size of an element. | |||
| 12451 | Sizes.push_back(ElementSize); | |||
| 12452 | ||||
| 12453 | LLVM_DEBUG({do { } while (false) | |||
| 12454 | dbgs() << "Sizes:\n";do { } while (false) | |||
| 12455 | for (const SCEV *S : Sizes)do { } while (false) | |||
| 12456 | dbgs() << *S << "\n";do { } while (false) | |||
| 12457 | })do { } while (false); | |||
| 12458 | } | |||
| 12459 | ||||
| 12460 | void ScalarEvolution::computeAccessFunctions( | |||
| 12461 | const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts, | |||
| 12462 | SmallVectorImpl<const SCEV *> &Sizes) { | |||
| 12463 | // Early exit in case this SCEV is not an affine multivariate function. | |||
| 12464 | if (Sizes.empty()) | |||
| 12465 | return; | |||
| 12466 | ||||
| 12467 | if (auto *AR = dyn_cast<SCEVAddRecExpr>(Expr)) | |||
| 12468 | if (!AR->isAffine()) | |||
| 12469 | return; | |||
| 12470 | ||||
| 12471 | const SCEV *Res = Expr; | |||
| 12472 | int Last = Sizes.size() - 1; | |||
| 12473 | for (int i = Last; i >= 0; i--) { | |||
| 12474 | const SCEV *Q, *R; | |||
| 12475 | SCEVDivision::divide(*this, Res, Sizes[i], &Q, &R); | |||
| 12476 | ||||
| 12477 | LLVM_DEBUG({do { } while (false) | |||
| 12478 | dbgs() << "Res: " << *Res << "\n";do { } while (false) | |||
| 12479 | dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";do { } while (false) | |||
| 12480 | dbgs() << "Res divided by Sizes[i]:\n";do { } while (false) | |||
| 12481 | dbgs() << "Quotient: " << *Q << "\n";do { } while (false) | |||
| 12482 | dbgs() << "Remainder: " << *R << "\n";do { } while (false) | |||
| 12483 | })do { } while (false); | |||
| 12484 | ||||
| 12485 | Res = Q; | |||
| 12486 | ||||
| 12487 | // Do not record the last subscript corresponding to the size of elements in | |||
| 12488 | // the array. | |||
| 12489 | if (i == Last) { | |||
| 12490 | ||||
| 12491 | // Bail out if the remainder is too complex. | |||
| 12492 | if (isa<SCEVAddRecExpr>(R)) { | |||
| 12493 | Subscripts.clear(); | |||
| 12494 | Sizes.clear(); | |||
| 12495 | return; | |||
| 12496 | } | |||
| 12497 | ||||
| 12498 | continue; | |||
| 12499 | } | |||
| 12500 | ||||
| 12501 | // Record the access function for the current subscript. | |||
| 12502 | Subscripts.push_back(R); | |||
| 12503 | } | |||
| 12504 | ||||
| 12505 | // Also push in last position the remainder of the last division: it will be | |||
| 12506 | // the access function of the innermost dimension. | |||
| 12507 | Subscripts.push_back(Res); | |||
| 12508 | ||||
| 12509 | std::reverse(Subscripts.begin(), Subscripts.end()); | |||
| 12510 | ||||
| 12511 | LLVM_DEBUG({do { } while (false) | |||
| 12512 | dbgs() << "Subscripts:\n";do { } while (false) | |||
| 12513 | for (const SCEV *S : Subscripts)do { } while (false) | |||
| 12514 | dbgs() << *S << "\n";do { } while (false) | |||
| 12515 | })do { } while (false); | |||
| 12516 | } | |||
| 12517 | ||||
| 12518 | /// Splits the SCEV into two vectors of SCEVs representing the subscripts and | |||
| 12519 | /// sizes of an array access. Returns the remainder of the delinearization that | |||
| 12520 | /// is the offset start of the array. The SCEV->delinearize algorithm computes | |||
| 12521 | /// the multiples of SCEV coefficients: that is a pattern matching of sub | |||
| 12522 | /// expressions in the stride and base of a SCEV corresponding to the | |||
| 12523 | /// computation of a GCD (greatest common divisor) of base and stride. When | |||
| 12524 | /// SCEV->delinearize fails, it returns the SCEV unchanged. | |||
| 12525 | /// | |||
| 12526 | /// For example: when analyzing the memory access A[i][j][k] in this loop nest | |||
| 12527 | /// | |||
| 12528 | /// void foo(long n, long m, long o, double A[n][m][o]) { | |||
| 12529 | /// | |||
| 12530 | /// for (long i = 0; i < n; i++) | |||
| 12531 | /// for (long j = 0; j < m; j++) | |||
| 12532 | /// for (long k = 0; k < o; k++) | |||
| 12533 | /// A[i][j][k] = 1.0; | |||
| 12534 | /// } | |||
| 12535 | /// | |||
| 12536 | /// the delinearization input is the following AddRec SCEV: | |||
| 12537 | /// | |||
| 12538 | /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k> | |||
| 12539 | /// | |||
| 12540 | /// From this SCEV, we are able to say that the base offset of the access is %A | |||
| 12541 | /// because it appears as an offset that does not divide any of the strides in | |||
| 12542 | /// the loops: | |||
| 12543 | /// | |||
| 12544 | /// CHECK: Base offset: %A | |||
| 12545 | /// | |||
| 12546 | /// and then SCEV->delinearize determines the size of some of the dimensions of | |||
| 12547 | /// the array as these are the multiples by which the strides are happening: | |||
| 12548 | /// | |||
| 12549 | /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes. | |||
| 12550 | /// | |||
| 12551 | /// Note that the outermost dimension remains of UnknownSize because there are | |||
| 12552 | /// no strides that would help identifying the size of the last dimension: when | |||
| 12553 | /// the array has been statically allocated, one could compute the size of that | |||
| 12554 | /// dimension by dividing the overall size of the array by the size of the known | |||
| 12555 | /// dimensions: %m * %o * 8. | |||
| 12556 | /// | |||
| 12557 | /// Finally delinearize provides the access functions for the array reference | |||
| 12558 | /// that does correspond to A[i][j][k] of the above C testcase: | |||
| 12559 | /// | |||
| 12560 | /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>] | |||
| 12561 | /// | |||
| 12562 | /// The testcases are checking the output of a function pass: | |||
| 12563 | /// DelinearizationPass that walks through all loads and stores of a function | |||
| 12564 | /// asking for the SCEV of the memory access with respect to all enclosing | |||
| 12565 | /// loops, calling SCEV->delinearize on that and printing the results. | |||
| 12566 | void ScalarEvolution::delinearize(const SCEV *Expr, | |||
| 12567 | SmallVectorImpl<const SCEV *> &Subscripts, | |||
| 12568 | SmallVectorImpl<const SCEV *> &Sizes, | |||
| 12569 | const SCEV *ElementSize) { | |||
| 12570 | // First step: collect parametric terms. | |||
| 12571 | SmallVector<const SCEV *, 4> Terms; | |||
| 12572 | collectParametricTerms(Expr, Terms); | |||
| 12573 | ||||
| 12574 | if (Terms.empty()) | |||
| 12575 | return; | |||
| 12576 | ||||
| 12577 | // Second step: find subscript sizes. | |||
| 12578 | findArrayDimensions(Terms, Sizes, ElementSize); | |||
| 12579 | ||||
| 12580 | if (Sizes.empty()) | |||
| 12581 | return; | |||
| 12582 | ||||
| 12583 | // Third step: compute the access functions for each subscript. | |||
| 12584 | computeAccessFunctions(Expr, Subscripts, Sizes); | |||
| 12585 | ||||
| 12586 | if (Subscripts.empty()) | |||
| 12587 | return; | |||
| 12588 | ||||
| 12589 | LLVM_DEBUG({do { } while (false) | |||
| 12590 | dbgs() << "succeeded to delinearize " << *Expr << "\n";do { } while (false) | |||
| 12591 | dbgs() << "ArrayDecl[UnknownSize]";do { } while (false) | |||
| 12592 | for (const SCEV *S : Sizes)do { } while (false) | |||
| 12593 | dbgs() << "[" << *S << "]";do { } while (false) | |||
| 12594 | ||||
| 12595 | dbgs() << "\nArrayRef";do { } while (false) | |||
| 12596 | for (const SCEV *S : Subscripts)do { } while (false) | |||
| 12597 | dbgs() << "[" << *S << "]";do { } while (false) | |||
| 12598 | dbgs() << "\n";do { } while (false) | |||
| 12599 | })do { } while (false); | |||
| 12600 | } | |||
| 12601 | ||||
| 12602 | bool ScalarEvolution::getIndexExpressionsFromGEP( | |||
| 12603 | const GetElementPtrInst *GEP, SmallVectorImpl<const SCEV *> &Subscripts, | |||
| 12604 | SmallVectorImpl<int> &Sizes) { | |||
| 12605 | assert(Subscripts.empty() && Sizes.empty() &&((void)0) | |||
| 12606 | "Expected output lists to be empty on entry to this function.")((void)0); | |||
| 12607 | assert(GEP && "getIndexExpressionsFromGEP called with a null GEP")((void)0); | |||
| 12608 | Type *Ty = nullptr; | |||
| 12609 | bool DroppedFirstDim = false; | |||
| 12610 | for (unsigned i = 1; i < GEP->getNumOperands(); i++) { | |||
| 12611 | const SCEV *Expr = getSCEV(GEP->getOperand(i)); | |||
| 12612 | if (i == 1) { | |||
| 12613 | Ty = GEP->getSourceElementType(); | |||
| 12614 | if (auto *Const = dyn_cast<SCEVConstant>(Expr)) | |||
| 12615 | if (Const->getValue()->isZero()) { | |||
| 12616 | DroppedFirstDim = true; | |||
| 12617 | continue; | |||
| 12618 | } | |||
| 12619 | Subscripts.push_back(Expr); | |||
| 12620 | continue; | |||
| 12621 | } | |||
| 12622 | ||||
| 12623 | auto *ArrayTy = dyn_cast<ArrayType>(Ty); | |||
| 12624 | if (!ArrayTy) { | |||
| 12625 | Subscripts.clear(); | |||
| 12626 | Sizes.clear(); | |||
| 12627 | return false; | |||
| 12628 | } | |||
| 12629 | ||||
| 12630 | Subscripts.push_back(Expr); | |||
| 12631 | if (!(DroppedFirstDim && i == 2)) | |||
| 12632 | Sizes.push_back(ArrayTy->getNumElements()); | |||
| 12633 | ||||
| 12634 | Ty = ArrayTy->getElementType(); | |||
| 12635 | } | |||
| 12636 | return !Subscripts.empty(); | |||
| 12637 | } | |||
| 12638 | ||||
| 12639 | //===----------------------------------------------------------------------===// | |||
| 12640 | // SCEVCallbackVH Class Implementation | |||
| 12641 | //===----------------------------------------------------------------------===// | |||
| 12642 | ||||
| 12643 | void ScalarEvolution::SCEVCallbackVH::deleted() { | |||
| 12644 | assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!")((void)0); | |||
| 12645 | if (PHINode *PN = dyn_cast<PHINode>(getValPtr())) | |||
| 12646 | SE->ConstantEvolutionLoopExitValue.erase(PN); | |||
| 12647 | SE->eraseValueFromMap(getValPtr()); | |||
| 12648 | // this now dangles! | |||
| 12649 | } | |||
| 12650 | ||||
| 12651 | void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) { | |||
| 12652 | assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!")((void)0); | |||
| 12653 | ||||
| 12654 | // Forget all the expressions associated with users of the old value, | |||
| 12655 | // so that future queries will recompute the expressions using the new | |||
| 12656 | // value. | |||
| 12657 | Value *Old = getValPtr(); | |||
| 12658 | SmallVector<User *, 16> Worklist(Old->users()); | |||
| 12659 | SmallPtrSet<User *, 8> Visited; | |||
| 12660 | while (!Worklist.empty()) { | |||
| 12661 | User *U = Worklist.pop_back_val(); | |||
| 12662 | // Deleting the Old value will cause this to dangle. Postpone | |||
| 12663 | // that until everything else is done. | |||
| 12664 | if (U == Old) | |||
| 12665 | continue; | |||
| 12666 | if (!Visited.insert(U).second) | |||
| 12667 | continue; | |||
| 12668 | if (PHINode *PN = dyn_cast<PHINode>(U)) | |||
| 12669 | SE->ConstantEvolutionLoopExitValue.erase(PN); | |||
| 12670 | SE->eraseValueFromMap(U); | |||
| 12671 | llvm::append_range(Worklist, U->users()); | |||
| 12672 | } | |||
| 12673 | // Delete the Old value. | |||
| 12674 | if (PHINode *PN = dyn_cast<PHINode>(Old)) | |||
| 12675 | SE->ConstantEvolutionLoopExitValue.erase(PN); | |||
| 12676 | SE->eraseValueFromMap(Old); | |||
| 12677 | // this now dangles! | |||
| 12678 | } | |||
| 12679 | ||||
| 12680 | ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se) | |||
| 12681 | : CallbackVH(V), SE(se) {} | |||
| 12682 | ||||
| 12683 | //===----------------------------------------------------------------------===// | |||
| 12684 | // ScalarEvolution Class Implementation | |||
| 12685 | //===----------------------------------------------------------------------===// | |||
| 12686 | ||||
| 12687 | ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI, | |||
| 12688 | AssumptionCache &AC, DominatorTree &DT, | |||
| 12689 | LoopInfo &LI) | |||
| 12690 | : F(F), TLI(TLI), AC(AC), DT(DT), LI(LI), | |||
| 12691 | CouldNotCompute(new SCEVCouldNotCompute()), ValuesAtScopes(64), | |||
| 12692 | LoopDispositions(64), BlockDispositions(64) { | |||
| 12693 | // To use guards for proving predicates, we need to scan every instruction in | |||
| 12694 | // relevant basic blocks, and not just terminators. Doing this is a waste of | |||
| 12695 | // time if the IR does not actually contain any calls to | |||
| 12696 | // @llvm.experimental.guard, so do a quick check and remember this beforehand. | |||
| 12697 | // | |||
| 12698 | // This pessimizes the case where a pass that preserves ScalarEvolution wants | |||
| 12699 | // to _add_ guards to the module when there weren't any before, and wants | |||
| 12700 | // ScalarEvolution to optimize based on those guards. For now we prefer to be | |||
| 12701 | // efficient in lieu of being smart in that rather obscure case. | |||
| 12702 | ||||
| 12703 | auto *GuardDecl = F.getParent()->getFunction( | |||
| 12704 | Intrinsic::getName(Intrinsic::experimental_guard)); | |||
| 12705 | HasGuards = GuardDecl && !GuardDecl->use_empty(); | |||
| 12706 | } | |||
| 12707 | ||||
| 12708 | ScalarEvolution::ScalarEvolution(ScalarEvolution &&Arg) | |||
| 12709 | : F(Arg.F), HasGuards(Arg.HasGuards), TLI(Arg.TLI), AC(Arg.AC), DT(Arg.DT), | |||
| 12710 | LI(Arg.LI), CouldNotCompute(std::move(Arg.CouldNotCompute)), | |||
| 12711 | ValueExprMap(std::move(Arg.ValueExprMap)), | |||
| 12712 | PendingLoopPredicates(std::move(Arg.PendingLoopPredicates)), | |||
| 12713 | PendingPhiRanges(std::move(Arg.PendingPhiRanges)), | |||
| 12714 | PendingMerges(std::move(Arg.PendingMerges)), | |||
| 12715 | MinTrailingZerosCache(std::move(Arg.MinTrailingZerosCache)), | |||
| 12716 | BackedgeTakenCounts(std::move(Arg.BackedgeTakenCounts)), | |||
| 12717 | PredicatedBackedgeTakenCounts( | |||
| 12718 | std::move(Arg.PredicatedBackedgeTakenCounts)), | |||
| 12719 | ConstantEvolutionLoopExitValue( | |||
| 12720 | std::move(Arg.ConstantEvolutionLoopExitValue)), | |||
| 12721 | ValuesAtScopes(std::move(Arg.ValuesAtScopes)), | |||
| 12722 | LoopDispositions(std::move(Arg.LoopDispositions)), | |||
| 12723 | LoopPropertiesCache(std::move(Arg.LoopPropertiesCache)), | |||
| 12724 | BlockDispositions(std::move(Arg.BlockDispositions)), | |||
| 12725 | UnsignedRanges(std::move(Arg.UnsignedRanges)), | |||
| 12726 | SignedRanges(std::move(Arg.SignedRanges)), | |||
| 12727 | UniqueSCEVs(std::move(Arg.UniqueSCEVs)), | |||
| 12728 | UniquePreds(std::move(Arg.UniquePreds)), | |||
| 12729 | SCEVAllocator(std::move(Arg.SCEVAllocator)), | |||
| 12730 | LoopUsers(std::move(Arg.LoopUsers)), | |||
| 12731 | PredicatedSCEVRewrites(std::move(Arg.PredicatedSCEVRewrites)), | |||
| 12732 | FirstUnknown(Arg.FirstUnknown) { | |||
| 12733 | Arg.FirstUnknown = nullptr; | |||
| 12734 | } | |||
| 12735 | ||||
| 12736 | ScalarEvolution::~ScalarEvolution() { | |||
| 12737 | // Iterate through all the SCEVUnknown instances and call their | |||
| 12738 | // destructors, so that they release their references to their values. | |||
| 12739 | for (SCEVUnknown *U = FirstUnknown; U;) { | |||
| 12740 | SCEVUnknown *Tmp = U; | |||
| 12741 | U = U->Next; | |||
| 12742 | Tmp->~SCEVUnknown(); | |||
| 12743 | } | |||
| 12744 | FirstUnknown = nullptr; | |||
| 12745 | ||||
| 12746 | ExprValueMap.clear(); | |||
| 12747 | ValueExprMap.clear(); | |||
| 12748 | HasRecMap.clear(); | |||
| 12749 | BackedgeTakenCounts.clear(); | |||
| 12750 | PredicatedBackedgeTakenCounts.clear(); | |||
| 12751 | ||||
| 12752 | assert(PendingLoopPredicates.empty() && "isImpliedCond garbage")((void)0); | |||
| 12753 | assert(PendingPhiRanges.empty() && "getRangeRef garbage")((void)0); | |||
| 12754 | assert(PendingMerges.empty() && "isImpliedViaMerge garbage")((void)0); | |||
| 12755 | assert(!WalkingBEDominatingConds && "isLoopBackedgeGuardedByCond garbage!")((void)0); | |||
| 12756 | assert(!ProvingSplitPredicate && "ProvingSplitPredicate garbage!")((void)0); | |||
| 12757 | } | |||
| 12758 | ||||
| 12759 | bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) { | |||
| 12760 | return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L)); | |||
| 12761 | } | |||
| 12762 | ||||
| 12763 | static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE, | |||
| 12764 | const Loop *L) { | |||
| 12765 | // Print all inner loops first | |||
| 12766 | for (Loop *I : *L) | |||
| 12767 | PrintLoopInfo(OS, SE, I); | |||
| 12768 | ||||
| 12769 | OS << "Loop "; | |||
| 12770 | L->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12771 | OS << ": "; | |||
| 12772 | ||||
| 12773 | SmallVector<BasicBlock *, 8> ExitingBlocks; | |||
| 12774 | L->getExitingBlocks(ExitingBlocks); | |||
| 12775 | if (ExitingBlocks.size() != 1) | |||
| 12776 | OS << "<multiple exits> "; | |||
| 12777 | ||||
| 12778 | if (SE->hasLoopInvariantBackedgeTakenCount(L)) | |||
| 12779 | OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L) << "\n"; | |||
| 12780 | else | |||
| 12781 | OS << "Unpredictable backedge-taken count.\n"; | |||
| 12782 | ||||
| 12783 | if (ExitingBlocks.size() > 1) | |||
| 12784 | for (BasicBlock *ExitingBlock : ExitingBlocks) { | |||
| 12785 | OS << " exit count for " << ExitingBlock->getName() << ": " | |||
| 12786 | << *SE->getExitCount(L, ExitingBlock) << "\n"; | |||
| 12787 | } | |||
| 12788 | ||||
| 12789 | OS << "Loop "; | |||
| 12790 | L->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12791 | OS << ": "; | |||
| 12792 | ||||
| 12793 | if (!isa<SCEVCouldNotCompute>(SE->getConstantMaxBackedgeTakenCount(L))) { | |||
| 12794 | OS << "max backedge-taken count is " << *SE->getConstantMaxBackedgeTakenCount(L); | |||
| 12795 | if (SE->isBackedgeTakenCountMaxOrZero(L)) | |||
| 12796 | OS << ", actual taken count either this or zero."; | |||
| 12797 | } else { | |||
| 12798 | OS << "Unpredictable max backedge-taken count. "; | |||
| 12799 | } | |||
| 12800 | ||||
| 12801 | OS << "\n" | |||
| 12802 | "Loop "; | |||
| 12803 | L->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12804 | OS << ": "; | |||
| 12805 | ||||
| 12806 | SCEVUnionPredicate Pred; | |||
| 12807 | auto PBT = SE->getPredicatedBackedgeTakenCount(L, Pred); | |||
| 12808 | if (!isa<SCEVCouldNotCompute>(PBT)) { | |||
| 12809 | OS << "Predicated backedge-taken count is " << *PBT << "\n"; | |||
| 12810 | OS << " Predicates:\n"; | |||
| 12811 | Pred.print(OS, 4); | |||
| 12812 | } else { | |||
| 12813 | OS << "Unpredictable predicated backedge-taken count. "; | |||
| 12814 | } | |||
| 12815 | OS << "\n"; | |||
| 12816 | ||||
| 12817 | if (SE->hasLoopInvariantBackedgeTakenCount(L)) { | |||
| 12818 | OS << "Loop "; | |||
| 12819 | L->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12820 | OS << ": "; | |||
| 12821 | OS << "Trip multiple is " << SE->getSmallConstantTripMultiple(L) << "\n"; | |||
| 12822 | } | |||
| 12823 | } | |||
| 12824 | ||||
| 12825 | static StringRef loopDispositionToStr(ScalarEvolution::LoopDisposition LD) { | |||
| 12826 | switch (LD) { | |||
| 12827 | case ScalarEvolution::LoopVariant: | |||
| 12828 | return "Variant"; | |||
| 12829 | case ScalarEvolution::LoopInvariant: | |||
| 12830 | return "Invariant"; | |||
| 12831 | case ScalarEvolution::LoopComputable: | |||
| 12832 | return "Computable"; | |||
| 12833 | } | |||
| 12834 | llvm_unreachable("Unknown ScalarEvolution::LoopDisposition kind!")__builtin_unreachable(); | |||
| 12835 | } | |||
| 12836 | ||||
| 12837 | void ScalarEvolution::print(raw_ostream &OS) const { | |||
| 12838 | // ScalarEvolution's implementation of the print method is to print | |||
| 12839 | // out SCEV values of all instructions that are interesting. Doing | |||
| 12840 | // this potentially causes it to create new SCEV objects though, | |||
| 12841 | // which technically conflicts with the const qualifier. This isn't | |||
| 12842 | // observable from outside the class though, so casting away the | |||
| 12843 | // const isn't dangerous. | |||
| 12844 | ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this); | |||
| 12845 | ||||
| 12846 | if (ClassifyExpressions) { | |||
| 12847 | OS << "Classifying expressions for: "; | |||
| 12848 | F.printAsOperand(OS, /*PrintType=*/false); | |||
| 12849 | OS << "\n"; | |||
| 12850 | for (Instruction &I : instructions(F)) | |||
| 12851 | if (isSCEVable(I.getType()) && !isa<CmpInst>(I)) { | |||
| 12852 | OS << I << '\n'; | |||
| 12853 | OS << " --> "; | |||
| 12854 | const SCEV *SV = SE.getSCEV(&I); | |||
| 12855 | SV->print(OS); | |||
| 12856 | if (!isa<SCEVCouldNotCompute>(SV)) { | |||
| 12857 | OS << " U: "; | |||
| 12858 | SE.getUnsignedRange(SV).print(OS); | |||
| 12859 | OS << " S: "; | |||
| 12860 | SE.getSignedRange(SV).print(OS); | |||
| 12861 | } | |||
| 12862 | ||||
| 12863 | const Loop *L = LI.getLoopFor(I.getParent()); | |||
| 12864 | ||||
| 12865 | const SCEV *AtUse = SE.getSCEVAtScope(SV, L); | |||
| 12866 | if (AtUse != SV) { | |||
| 12867 | OS << " --> "; | |||
| 12868 | AtUse->print(OS); | |||
| 12869 | if (!isa<SCEVCouldNotCompute>(AtUse)) { | |||
| 12870 | OS << " U: "; | |||
| 12871 | SE.getUnsignedRange(AtUse).print(OS); | |||
| 12872 | OS << " S: "; | |||
| 12873 | SE.getSignedRange(AtUse).print(OS); | |||
| 12874 | } | |||
| 12875 | } | |||
| 12876 | ||||
| 12877 | if (L) { | |||
| 12878 | OS << "\t\t" "Exits: "; | |||
| 12879 | const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop()); | |||
| 12880 | if (!SE.isLoopInvariant(ExitValue, L)) { | |||
| 12881 | OS << "<<Unknown>>"; | |||
| 12882 | } else { | |||
| 12883 | OS << *ExitValue; | |||
| 12884 | } | |||
| 12885 | ||||
| 12886 | bool First = true; | |||
| 12887 | for (auto *Iter = L; Iter; Iter = Iter->getParentLoop()) { | |||
| 12888 | if (First) { | |||
| 12889 | OS << "\t\t" "LoopDispositions: { "; | |||
| 12890 | First = false; | |||
| 12891 | } else { | |||
| 12892 | OS << ", "; | |||
| 12893 | } | |||
| 12894 | ||||
| 12895 | Iter->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12896 | OS << ": " << loopDispositionToStr(SE.getLoopDisposition(SV, Iter)); | |||
| 12897 | } | |||
| 12898 | ||||
| 12899 | for (auto *InnerL : depth_first(L)) { | |||
| 12900 | if (InnerL == L) | |||
| 12901 | continue; | |||
| 12902 | if (First) { | |||
| 12903 | OS << "\t\t" "LoopDispositions: { "; | |||
| 12904 | First = false; | |||
| 12905 | } else { | |||
| 12906 | OS << ", "; | |||
| 12907 | } | |||
| 12908 | ||||
| 12909 | InnerL->getHeader()->printAsOperand(OS, /*PrintType=*/false); | |||
| 12910 | OS << ": " << loopDispositionToStr(SE.getLoopDisposition(SV, InnerL)); | |||
| 12911 | } | |||
| 12912 | ||||
| 12913 | OS << " }"; | |||
| 12914 | } | |||
| 12915 | ||||
| 12916 | OS << "\n"; | |||
| 12917 | } | |||
| 12918 | } | |||
| 12919 | ||||
| 12920 | OS << "Determining loop execution counts for: "; | |||
| 12921 | F.printAsOperand(OS, /*PrintType=*/false); | |||
| 12922 | OS << "\n"; | |||
| 12923 | for (Loop *I : LI) | |||
| 12924 | PrintLoopInfo(OS, &SE, I); | |||
| 12925 | } | |||
| 12926 | ||||
| 12927 | ScalarEvolution::LoopDisposition | |||
| 12928 | ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) { | |||
| 12929 | auto &Values = LoopDispositions[S]; | |||
| 12930 | for (auto &V : Values) { | |||
| 12931 | if (V.getPointer() == L) | |||
| 12932 | return V.getInt(); | |||
| 12933 | } | |||
| 12934 | Values.emplace_back(L, LoopVariant); | |||
| 12935 | LoopDisposition D = computeLoopDisposition(S, L); | |||
| 12936 | auto &Values2 = LoopDispositions[S]; | |||
| 12937 | for (auto &V : make_range(Values2.rbegin(), Values2.rend())) { | |||
| 12938 | if (V.getPointer() == L) { | |||
| 12939 | V.setInt(D); | |||
| 12940 | break; | |||
| 12941 | } | |||
| 12942 | } | |||
| 12943 | return D; | |||
| 12944 | } | |||
| 12945 | ||||
| 12946 | ScalarEvolution::LoopDisposition | |||
| 12947 | ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) { | |||
| 12948 | switch (S->getSCEVType()) { | |||
| 12949 | case scConstant: | |||
| 12950 | return LoopInvariant; | |||
| 12951 | case scPtrToInt: | |||
| 12952 | case scTruncate: | |||
| 12953 | case scZeroExtend: | |||
| 12954 | case scSignExtend: | |||
| 12955 | return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L); | |||
| 12956 | case scAddRecExpr: { | |||
| 12957 | const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S); | |||
| 12958 | ||||
| 12959 | // If L is the addrec's loop, it's computable. | |||
| 12960 | if (AR->getLoop() == L) | |||
| 12961 | return LoopComputable; | |||
| 12962 | ||||
| 12963 | // Add recurrences are never invariant in the function-body (null loop). | |||
| 12964 | if (!L) | |||
| 12965 | return LoopVariant; | |||
| 12966 | ||||
| 12967 | // Everything that is not defined at loop entry is variant. | |||
| 12968 | if (DT.dominates(L->getHeader(), AR->getLoop()->getHeader())) | |||
| 12969 | return LoopVariant; | |||
| 12970 | assert(!L->contains(AR->getLoop()) && "Containing loop's header does not"((void)0) | |||
| 12971 | " dominate the contained loop's header?")((void)0); | |||
| 12972 | ||||
| 12973 | // This recurrence is invariant w.r.t. L if AR's loop contains L. | |||
| 12974 | if (AR->getLoop()->contains(L)) | |||
| 12975 | return LoopInvariant; | |||
| 12976 | ||||
| 12977 | // This recurrence is variant w.r.t. L if any of its operands | |||
| 12978 | // are variant. | |||
| 12979 | for (auto *Op : AR->operands()) | |||
| 12980 | if (!isLoopInvariant(Op, L)) | |||
| 12981 | return LoopVariant; | |||
| 12982 | ||||
| 12983 | // Otherwise it's loop-invariant. | |||
| 12984 | return LoopInvariant; | |||
| 12985 | } | |||
| 12986 | case scAddExpr: | |||
| 12987 | case scMulExpr: | |||
| 12988 | case scUMaxExpr: | |||
| 12989 | case scSMaxExpr: | |||
| 12990 | case scUMinExpr: | |||
| 12991 | case scSMinExpr: { | |||
| 12992 | bool HasVarying = false; | |||
| 12993 | for (auto *Op : cast<SCEVNAryExpr>(S)->operands()) { | |||
| 12994 | LoopDisposition D = getLoopDisposition(Op, L); | |||
| 12995 | if (D == LoopVariant) | |||
| 12996 | return LoopVariant; | |||
| 12997 | if (D == LoopComputable) | |||
| 12998 | HasVarying = true; | |||
| 12999 | } | |||
| 13000 | return HasVarying ? LoopComputable : LoopInvariant; | |||
| 13001 | } | |||
| 13002 | case scUDivExpr: { | |||
| 13003 | const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S); | |||
| 13004 | LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L); | |||
| 13005 | if (LD == LoopVariant) | |||
| 13006 | return LoopVariant; | |||
| 13007 | LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L); | |||
| 13008 | if (RD == LoopVariant) | |||
| 13009 | return LoopVariant; | |||
| 13010 | return (LD == LoopInvariant && RD == LoopInvariant) ? | |||
| 13011 | LoopInvariant : LoopComputable; | |||
| 13012 | } | |||
| 13013 | case scUnknown: | |||
| 13014 | // All non-instruction values are loop invariant. All instructions are loop | |||
| 13015 | // invariant if they are not contained in the specified loop. | |||
| 13016 | // Instructions are never considered invariant in the function body | |||
| 13017 | // (null loop) because they are defined within the "loop". | |||
| 13018 | if (auto *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) | |||
| 13019 | return (L && !L->contains(I)) ? LoopInvariant : LoopVariant; | |||
| 13020 | return LoopInvariant; | |||
| 13021 | case scCouldNotCompute: | |||
| 13022 | llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")__builtin_unreachable(); | |||
| 13023 | } | |||
| 13024 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 13025 | } | |||
| 13026 | ||||
| 13027 | bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) { | |||
| 13028 | return getLoopDisposition(S, L) == LoopInvariant; | |||
| 13029 | } | |||
| 13030 | ||||
| 13031 | bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) { | |||
| 13032 | return getLoopDisposition(S, L) == LoopComputable; | |||
| 13033 | } | |||
| 13034 | ||||
| 13035 | ScalarEvolution::BlockDisposition | |||
| 13036 | ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) { | |||
| 13037 | auto &Values = BlockDispositions[S]; | |||
| 13038 | for (auto &V : Values) { | |||
| 13039 | if (V.getPointer() == BB) | |||
| 13040 | return V.getInt(); | |||
| 13041 | } | |||
| 13042 | Values.emplace_back(BB, DoesNotDominateBlock); | |||
| 13043 | BlockDisposition D = computeBlockDisposition(S, BB); | |||
| 13044 | auto &Values2 = BlockDispositions[S]; | |||
| 13045 | for (auto &V : make_range(Values2.rbegin(), Values2.rend())) { | |||
| 13046 | if (V.getPointer() == BB) { | |||
| 13047 | V.setInt(D); | |||
| 13048 | break; | |||
| 13049 | } | |||
| 13050 | } | |||
| 13051 | return D; | |||
| 13052 | } | |||
| 13053 | ||||
| 13054 | ScalarEvolution::BlockDisposition | |||
| 13055 | ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) { | |||
| 13056 | switch (S->getSCEVType()) { | |||
| 13057 | case scConstant: | |||
| 13058 | return ProperlyDominatesBlock; | |||
| 13059 | case scPtrToInt: | |||
| 13060 | case scTruncate: | |||
| 13061 | case scZeroExtend: | |||
| 13062 | case scSignExtend: | |||
| 13063 | return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB); | |||
| 13064 | case scAddRecExpr: { | |||
| 13065 | // This uses a "dominates" query instead of "properly dominates" query | |||
| 13066 | // to test for proper dominance too, because the instruction which | |||
| 13067 | // produces the addrec's value is a PHI, and a PHI effectively properly | |||
| 13068 | // dominates its entire containing block. | |||
| 13069 | const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S); | |||
| 13070 | if (!DT.dominates(AR->getLoop()->getHeader(), BB)) | |||
| 13071 | return DoesNotDominateBlock; | |||
| 13072 | ||||
| 13073 | // Fall through into SCEVNAryExpr handling. | |||
| 13074 | LLVM_FALLTHROUGH[[gnu::fallthrough]]; | |||
| 13075 | } | |||
| 13076 | case scAddExpr: | |||
| 13077 | case scMulExpr: | |||
| 13078 | case scUMaxExpr: | |||
| 13079 | case scSMaxExpr: | |||
| 13080 | case scUMinExpr: | |||
| 13081 | case scSMinExpr: { | |||
| 13082 | const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S); | |||
| 13083 | bool Proper = true; | |||
| 13084 | for (const SCEV *NAryOp : NAry->operands()) { | |||
| 13085 | BlockDisposition D = getBlockDisposition(NAryOp, BB); | |||
| 13086 | if (D == DoesNotDominateBlock) | |||
| 13087 | return DoesNotDominateBlock; | |||
| 13088 | if (D == DominatesBlock) | |||
| 13089 | Proper = false; | |||
| 13090 | } | |||
| 13091 | return Proper ? ProperlyDominatesBlock : DominatesBlock; | |||
| 13092 | } | |||
| 13093 | case scUDivExpr: { | |||
| 13094 | const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S); | |||
| 13095 | const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS(); | |||
| 13096 | BlockDisposition LD = getBlockDisposition(LHS, BB); | |||
| 13097 | if (LD == DoesNotDominateBlock) | |||
| 13098 | return DoesNotDominateBlock; | |||
| 13099 | BlockDisposition RD = getBlockDisposition(RHS, BB); | |||
| 13100 | if (RD == DoesNotDominateBlock) | |||
| 13101 | return DoesNotDominateBlock; | |||
| 13102 | return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ? | |||
| 13103 | ProperlyDominatesBlock : DominatesBlock; | |||
| 13104 | } | |||
| 13105 | case scUnknown: | |||
| 13106 | if (Instruction *I = | |||
| 13107 | dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) { | |||
| 13108 | if (I->getParent() == BB) | |||
| 13109 | return DominatesBlock; | |||
| 13110 | if (DT.properlyDominates(I->getParent(), BB)) | |||
| 13111 | return ProperlyDominatesBlock; | |||
| 13112 | return DoesNotDominateBlock; | |||
| 13113 | } | |||
| 13114 | return ProperlyDominatesBlock; | |||
| 13115 | case scCouldNotCompute: | |||
| 13116 | llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")__builtin_unreachable(); | |||
| 13117 | } | |||
| 13118 | llvm_unreachable("Unknown SCEV kind!")__builtin_unreachable(); | |||
| 13119 | } | |||
| 13120 | ||||
| 13121 | bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) { | |||
| 13122 | return getBlockDisposition(S, BB) >= DominatesBlock; | |||
| 13123 | } | |||
| 13124 | ||||
| 13125 | bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) { | |||
| 13126 | return getBlockDisposition(S, BB) == ProperlyDominatesBlock; | |||
| 13127 | } | |||
| 13128 | ||||
| 13129 | bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const { | |||
| 13130 | return SCEVExprContains(S, [&](const SCEV *Expr) { return Expr == Op; }); | |||
| 13131 | } | |||
| 13132 | ||||
| 13133 | void | |||
| 13134 | ScalarEvolution::forgetMemoizedResults(const SCEV *S) { | |||
| 13135 | ValuesAtScopes.erase(S); | |||
| 13136 | LoopDispositions.erase(S); | |||
| 13137 | BlockDispositions.erase(S); | |||
| 13138 | UnsignedRanges.erase(S); | |||
| 13139 | SignedRanges.erase(S); | |||
| 13140 | ExprValueMap.erase(S); | |||
| 13141 | HasRecMap.erase(S); | |||
| 13142 | MinTrailingZerosCache.erase(S); | |||
| 13143 | ||||
| 13144 | for (auto I = PredicatedSCEVRewrites.begin(); | |||
| 13145 | I != PredicatedSCEVRewrites.end();) { | |||
| 13146 | std::pair<const SCEV *, const Loop *> Entry = I->first; | |||
| 13147 | if (Entry.first == S) | |||
| 13148 | PredicatedSCEVRewrites.erase(I++); | |||
| 13149 | else | |||
| 13150 | ++I; | |||
| 13151 | } | |||
| 13152 | ||||
| 13153 | auto RemoveSCEVFromBackedgeMap = | |||
| 13154 | [S](DenseMap<const Loop *, BackedgeTakenInfo> &Map) { | |||
| 13155 | for (auto I = Map.begin(), E = Map.end(); I != E;) { | |||
| 13156 | BackedgeTakenInfo &BEInfo = I->second; | |||
| 13157 | if (BEInfo.hasOperand(S)) | |||
| 13158 | Map.erase(I++); | |||
| 13159 | else | |||
| 13160 | ++I; | |||
| 13161 | } | |||
| 13162 | }; | |||
| 13163 | ||||
| 13164 | RemoveSCEVFromBackedgeMap(BackedgeTakenCounts); | |||
| 13165 | RemoveSCEVFromBackedgeMap(PredicatedBackedgeTakenCounts); | |||
| 13166 | } | |||
| 13167 | ||||
| 13168 | void | |||
| 13169 | ScalarEvolution::getUsedLoops(const SCEV *S, | |||
| 13170 | SmallPtrSetImpl<const Loop *> &LoopsUsed) { | |||
| 13171 | struct FindUsedLoops { | |||
| 13172 | FindUsedLoops(SmallPtrSetImpl<const Loop *> &LoopsUsed) | |||
| 13173 | : LoopsUsed(LoopsUsed) {} | |||
| 13174 | SmallPtrSetImpl<const Loop *> &LoopsUsed; | |||
| 13175 | bool follow(const SCEV *S) { | |||
| 13176 | if (auto *AR = dyn_cast<SCEVAddRecExpr>(S)) | |||
| 13177 | LoopsUsed.insert(AR->getLoop()); | |||
| 13178 | return true; | |||
| 13179 | } | |||
| 13180 | ||||
| 13181 | bool isDone() const { return false; } | |||
| 13182 | }; | |||
| 13183 | ||||
| 13184 | FindUsedLoops F(LoopsUsed); | |||
| 13185 | SCEVTraversal<FindUsedLoops>(F).visitAll(S); | |||
| 13186 | } | |||
| 13187 | ||||
| 13188 | void ScalarEvolution::addToLoopUseLists(const SCEV *S) { | |||
| 13189 | SmallPtrSet<const Loop *, 8> LoopsUsed; | |||
| 13190 | getUsedLoops(S, LoopsUsed); | |||
| 13191 | for (auto *L : LoopsUsed) | |||
| 13192 | LoopUsers[L].push_back(S); | |||
| 13193 | } | |||
| 13194 | ||||
| 13195 | void ScalarEvolution::verify() const { | |||
| 13196 | ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this); | |||
| 13197 | ScalarEvolution SE2(F, TLI, AC, DT, LI); | |||
| 13198 | ||||
| 13199 | SmallVector<Loop *, 8> LoopStack(LI.begin(), LI.end()); | |||
| 13200 | ||||
| 13201 | // Map's SCEV expressions from one ScalarEvolution "universe" to another. | |||
| 13202 | struct SCEVMapper : public SCEVRewriteVisitor<SCEVMapper> { | |||
| 13203 | SCEVMapper(ScalarEvolution &SE) : SCEVRewriteVisitor<SCEVMapper>(SE) {} | |||
| 13204 | ||||
| 13205 | const SCEV *visitConstant(const SCEVConstant *Constant) { | |||
| 13206 | return SE.getConstant(Constant->getAPInt()); | |||
| 13207 | } | |||
| 13208 | ||||
| 13209 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 13210 | return SE.getUnknown(Expr->getValue()); | |||
| 13211 | } | |||
| 13212 | ||||
| 13213 | const SCEV *visitCouldNotCompute(const SCEVCouldNotCompute *Expr) { | |||
| 13214 | return SE.getCouldNotCompute(); | |||
| 13215 | } | |||
| 13216 | }; | |||
| 13217 | ||||
| 13218 | SCEVMapper SCM(SE2); | |||
| 13219 | ||||
| 13220 | while (!LoopStack.empty()) { | |||
| 13221 | auto *L = LoopStack.pop_back_val(); | |||
| 13222 | llvm::append_range(LoopStack, *L); | |||
| 13223 | ||||
| 13224 | auto *CurBECount = SCM.visit( | |||
| 13225 | const_cast<ScalarEvolution *>(this)->getBackedgeTakenCount(L)); | |||
| 13226 | auto *NewBECount = SE2.getBackedgeTakenCount(L); | |||
| 13227 | ||||
| 13228 | if (CurBECount == SE2.getCouldNotCompute() || | |||
| 13229 | NewBECount == SE2.getCouldNotCompute()) { | |||
| 13230 | // NB! This situation is legal, but is very suspicious -- whatever pass | |||
| 13231 | // change the loop to make a trip count go from could not compute to | |||
| 13232 | // computable or vice-versa *should have* invalidated SCEV. However, we | |||
| 13233 | // choose not to assert here (for now) since we don't want false | |||
| 13234 | // positives. | |||
| 13235 | continue; | |||
| 13236 | } | |||
| 13237 | ||||
| 13238 | if (containsUndefs(CurBECount) || containsUndefs(NewBECount)) { | |||
| 13239 | // SCEV treats "undef" as an unknown but consistent value (i.e. it does | |||
| 13240 | // not propagate undef aggressively). This means we can (and do) fail | |||
| 13241 | // verification in cases where a transform makes the trip count of a loop | |||
| 13242 | // go from "undef" to "undef+1" (say). The transform is fine, since in | |||
| 13243 | // both cases the loop iterates "undef" times, but SCEV thinks we | |||
| 13244 | // increased the trip count of the loop by 1 incorrectly. | |||
| 13245 | continue; | |||
| 13246 | } | |||
| 13247 | ||||
| 13248 | if (SE.getTypeSizeInBits(CurBECount->getType()) > | |||
| 13249 | SE.getTypeSizeInBits(NewBECount->getType())) | |||
| 13250 | NewBECount = SE2.getZeroExtendExpr(NewBECount, CurBECount->getType()); | |||
| 13251 | else if (SE.getTypeSizeInBits(CurBECount->getType()) < | |||
| 13252 | SE.getTypeSizeInBits(NewBECount->getType())) | |||
| 13253 | CurBECount = SE2.getZeroExtendExpr(CurBECount, NewBECount->getType()); | |||
| 13254 | ||||
| 13255 | const SCEV *Delta = SE2.getMinusSCEV(CurBECount, NewBECount); | |||
| 13256 | ||||
| 13257 | // Unless VerifySCEVStrict is set, we only compare constant deltas. | |||
| 13258 | if ((VerifySCEVStrict || isa<SCEVConstant>(Delta)) && !Delta->isZero()) { | |||
| 13259 | dbgs() << "Trip Count for " << *L << " Changed!\n"; | |||
| 13260 | dbgs() << "Old: " << *CurBECount << "\n"; | |||
| 13261 | dbgs() << "New: " << *NewBECount << "\n"; | |||
| 13262 | dbgs() << "Delta: " << *Delta << "\n"; | |||
| 13263 | std::abort(); | |||
| 13264 | } | |||
| 13265 | } | |||
| 13266 | ||||
| 13267 | // Collect all valid loops currently in LoopInfo. | |||
| 13268 | SmallPtrSet<Loop *, 32> ValidLoops; | |||
| 13269 | SmallVector<Loop *, 32> Worklist(LI.begin(), LI.end()); | |||
| 13270 | while (!Worklist.empty()) { | |||
| 13271 | Loop *L = Worklist.pop_back_val(); | |||
| 13272 | if (ValidLoops.contains(L)) | |||
| 13273 | continue; | |||
| 13274 | ValidLoops.insert(L); | |||
| 13275 | Worklist.append(L->begin(), L->end()); | |||
| 13276 | } | |||
| 13277 | // Check for SCEV expressions referencing invalid/deleted loops. | |||
| 13278 | for (auto &KV : ValueExprMap) { | |||
| 13279 | auto *AR = dyn_cast<SCEVAddRecExpr>(KV.second); | |||
| 13280 | if (!AR) | |||
| 13281 | continue; | |||
| 13282 | assert(ValidLoops.contains(AR->getLoop()) &&((void)0) | |||
| 13283 | "AddRec references invalid loop")((void)0); | |||
| 13284 | } | |||
| 13285 | } | |||
| 13286 | ||||
| 13287 | bool ScalarEvolution::invalidate( | |||
| 13288 | Function &F, const PreservedAnalyses &PA, | |||
| 13289 | FunctionAnalysisManager::Invalidator &Inv) { | |||
| 13290 | // Invalidate the ScalarEvolution object whenever it isn't preserved or one | |||
| 13291 | // of its dependencies is invalidated. | |||
| 13292 | auto PAC = PA.getChecker<ScalarEvolutionAnalysis>(); | |||
| 13293 | return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) || | |||
| 13294 | Inv.invalidate<AssumptionAnalysis>(F, PA) || | |||
| 13295 | Inv.invalidate<DominatorTreeAnalysis>(F, PA) || | |||
| 13296 | Inv.invalidate<LoopAnalysis>(F, PA); | |||
| 13297 | } | |||
| 13298 | ||||
| 13299 | AnalysisKey ScalarEvolutionAnalysis::Key; | |||
| 13300 | ||||
| 13301 | ScalarEvolution ScalarEvolutionAnalysis::run(Function &F, | |||
| 13302 | FunctionAnalysisManager &AM) { | |||
| 13303 | return ScalarEvolution(F, AM.getResult<TargetLibraryAnalysis>(F), | |||
| 13304 | AM.getResult<AssumptionAnalysis>(F), | |||
| 13305 | AM.getResult<DominatorTreeAnalysis>(F), | |||
| 13306 | AM.getResult<LoopAnalysis>(F)); | |||
| 13307 | } | |||
| 13308 | ||||
| 13309 | PreservedAnalyses | |||
| 13310 | ScalarEvolutionVerifierPass::run(Function &F, FunctionAnalysisManager &AM) { | |||
| 13311 | AM.getResult<ScalarEvolutionAnalysis>(F).verify(); | |||
| 13312 | return PreservedAnalyses::all(); | |||
| 13313 | } | |||
| 13314 | ||||
| 13315 | PreservedAnalyses | |||
| 13316 | ScalarEvolutionPrinterPass::run(Function &F, FunctionAnalysisManager &AM) { | |||
| 13317 | // For compatibility with opt's -analyze feature under legacy pass manager | |||
| 13318 | // which was not ported to NPM. This keeps tests using | |||
| 13319 | // update_analyze_test_checks.py working. | |||
| 13320 | OS << "Printing analysis 'Scalar Evolution Analysis' for function '" | |||
| 13321 | << F.getName() << "':\n"; | |||
| 13322 | AM.getResult<ScalarEvolutionAnalysis>(F).print(OS); | |||
| 13323 | return PreservedAnalyses::all(); | |||
| 13324 | } | |||
| 13325 | ||||
| 13326 | INITIALIZE_PASS_BEGIN(ScalarEvolutionWrapperPass, "scalar-evolution",static void *initializeScalarEvolutionWrapperPassPassOnce(PassRegistry &Registry) { | |||
| 13327 | "Scalar Evolution Analysis", false, true)static void *initializeScalarEvolutionWrapperPassPassOnce(PassRegistry &Registry) { | |||
| 13328 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | |||
| 13329 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | |||
| 13330 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | |||
| 13331 | INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry); | |||
| 13332 | INITIALIZE_PASS_END(ScalarEvolutionWrapperPass, "scalar-evolution",PassInfo *PI = new PassInfo( "Scalar Evolution Analysis", "scalar-evolution" , &ScalarEvolutionWrapperPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<ScalarEvolutionWrapperPass>), false, true ); Registry.registerPass(*PI, true); return PI; } static llvm ::once_flag InitializeScalarEvolutionWrapperPassPassFlag; void llvm::initializeScalarEvolutionWrapperPassPass(PassRegistry & Registry) { llvm::call_once(InitializeScalarEvolutionWrapperPassPassFlag , initializeScalarEvolutionWrapperPassPassOnce, std::ref(Registry )); } | |||
| 13333 | "Scalar Evolution Analysis", false, true)PassInfo *PI = new PassInfo( "Scalar Evolution Analysis", "scalar-evolution" , &ScalarEvolutionWrapperPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<ScalarEvolutionWrapperPass>), false, true ); Registry.registerPass(*PI, true); return PI; } static llvm ::once_flag InitializeScalarEvolutionWrapperPassPassFlag; void llvm::initializeScalarEvolutionWrapperPassPass(PassRegistry & Registry) { llvm::call_once(InitializeScalarEvolutionWrapperPassPassFlag , initializeScalarEvolutionWrapperPassPassOnce, std::ref(Registry )); } | |||
| 13334 | ||||
| 13335 | char ScalarEvolutionWrapperPass::ID = 0; | |||
| 13336 | ||||
| 13337 | ScalarEvolutionWrapperPass::ScalarEvolutionWrapperPass() : FunctionPass(ID) { | |||
| 13338 | initializeScalarEvolutionWrapperPassPass(*PassRegistry::getPassRegistry()); | |||
| 13339 | } | |||
| 13340 | ||||
| 13341 | bool ScalarEvolutionWrapperPass::runOnFunction(Function &F) { | |||
| 13342 | SE.reset(new ScalarEvolution( | |||
| 13343 | F, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F), | |||
| 13344 | getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F), | |||
| 13345 | getAnalysis<DominatorTreeWrapperPass>().getDomTree(), | |||
| 13346 | getAnalysis<LoopInfoWrapperPass>().getLoopInfo())); | |||
| 13347 | return false; | |||
| 13348 | } | |||
| 13349 | ||||
| 13350 | void ScalarEvolutionWrapperPass::releaseMemory() { SE.reset(); } | |||
| 13351 | ||||
| 13352 | void ScalarEvolutionWrapperPass::print(raw_ostream &OS, const Module *) const { | |||
| 13353 | SE->print(OS); | |||
| 13354 | } | |||
| 13355 | ||||
| 13356 | void ScalarEvolutionWrapperPass::verifyAnalysis() const { | |||
| 13357 | if (!VerifySCEV) | |||
| 13358 | return; | |||
| 13359 | ||||
| 13360 | SE->verify(); | |||
| 13361 | } | |||
| 13362 | ||||
| 13363 | void ScalarEvolutionWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { | |||
| 13364 | AU.setPreservesAll(); | |||
| 13365 | AU.addRequiredTransitive<AssumptionCacheTracker>(); | |||
| 13366 | AU.addRequiredTransitive<LoopInfoWrapperPass>(); | |||
| 13367 | AU.addRequiredTransitive<DominatorTreeWrapperPass>(); | |||
| 13368 | AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>(); | |||
| 13369 | } | |||
| 13370 | ||||
| 13371 | const SCEVPredicate *ScalarEvolution::getEqualPredicate(const SCEV *LHS, | |||
| 13372 | const SCEV *RHS) { | |||
| 13373 | FoldingSetNodeID ID; | |||
| 13374 | assert(LHS->getType() == RHS->getType() &&((void)0) | |||
| 13375 | "Type mismatch between LHS and RHS")((void)0); | |||
| 13376 | // Unique this node based on the arguments | |||
| 13377 | ID.AddInteger(SCEVPredicate::P_Equal); | |||
| 13378 | ID.AddPointer(LHS); | |||
| 13379 | ID.AddPointer(RHS); | |||
| 13380 | void *IP = nullptr; | |||
| 13381 | if (const auto *S = UniquePreds.FindNodeOrInsertPos(ID, IP)) | |||
| 13382 | return S; | |||
| 13383 | SCEVEqualPredicate *Eq = new (SCEVAllocator) | |||
| 13384 | SCEVEqualPredicate(ID.Intern(SCEVAllocator), LHS, RHS); | |||
| 13385 | UniquePreds.InsertNode(Eq, IP); | |||
| 13386 | return Eq; | |||
| 13387 | } | |||
| 13388 | ||||
| 13389 | const SCEVPredicate *ScalarEvolution::getWrapPredicate( | |||
| 13390 | const SCEVAddRecExpr *AR, | |||
| 13391 | SCEVWrapPredicate::IncrementWrapFlags AddedFlags) { | |||
| 13392 | FoldingSetNodeID ID; | |||
| 13393 | // Unique this node based on the arguments | |||
| 13394 | ID.AddInteger(SCEVPredicate::P_Wrap); | |||
| 13395 | ID.AddPointer(AR); | |||
| 13396 | ID.AddInteger(AddedFlags); | |||
| 13397 | void *IP = nullptr; | |||
| 13398 | if (const auto *S = UniquePreds.FindNodeOrInsertPos(ID, IP)) | |||
| 13399 | return S; | |||
| 13400 | auto *OF = new (SCEVAllocator) | |||
| 13401 | SCEVWrapPredicate(ID.Intern(SCEVAllocator), AR, AddedFlags); | |||
| 13402 | UniquePreds.InsertNode(OF, IP); | |||
| 13403 | return OF; | |||
| 13404 | } | |||
| 13405 | ||||
| 13406 | namespace { | |||
| 13407 | ||||
| 13408 | class SCEVPredicateRewriter : public SCEVRewriteVisitor<SCEVPredicateRewriter> { | |||
| 13409 | public: | |||
| 13410 | ||||
| 13411 | /// Rewrites \p S in the context of a loop L and the SCEV predication | |||
| 13412 | /// infrastructure. | |||
| 13413 | /// | |||
| 13414 | /// If \p Pred is non-null, the SCEV expression is rewritten to respect the | |||
| 13415 | /// equivalences present in \p Pred. | |||
| 13416 | /// | |||
| 13417 | /// If \p NewPreds is non-null, rewrite is free to add further predicates to | |||
| 13418 | /// \p NewPreds such that the result will be an AddRecExpr. | |||
| 13419 | static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE, | |||
| 13420 | SmallPtrSetImpl<const SCEVPredicate *> *NewPreds, | |||
| 13421 | SCEVUnionPredicate *Pred) { | |||
| 13422 | SCEVPredicateRewriter Rewriter(L, SE, NewPreds, Pred); | |||
| 13423 | return Rewriter.visit(S); | |||
| 13424 | } | |||
| 13425 | ||||
| 13426 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 13427 | if (Pred) { | |||
| 13428 | auto ExprPreds = Pred->getPredicatesForExpr(Expr); | |||
| 13429 | for (auto *Pred : ExprPreds) | |||
| 13430 | if (const auto *IPred = dyn_cast<SCEVEqualPredicate>(Pred)) | |||
| 13431 | if (IPred->getLHS() == Expr) | |||
| 13432 | return IPred->getRHS(); | |||
| 13433 | } | |||
| 13434 | return convertToAddRecWithPreds(Expr); | |||
| 13435 | } | |||
| 13436 | ||||
| 13437 | const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) { | |||
| 13438 | const SCEV *Operand = visit(Expr->getOperand()); | |||
| 13439 | const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Operand); | |||
| 13440 | if (AR && AR->getLoop() == L && AR->isAffine()) { | |||
| 13441 | // This couldn't be folded because the operand didn't have the nuw | |||
| 13442 | // flag. Add the nusw flag as an assumption that we could make. | |||
| 13443 | const SCEV *Step = AR->getStepRecurrence(SE); | |||
| 13444 | Type *Ty = Expr->getType(); | |||
| 13445 | if (addOverflowAssumption(AR, SCEVWrapPredicate::IncrementNUSW)) | |||
| 13446 | return SE.getAddRecExpr(SE.getZeroExtendExpr(AR->getStart(), Ty), | |||
| 13447 | SE.getSignExtendExpr(Step, Ty), L, | |||
| 13448 | AR->getNoWrapFlags()); | |||
| 13449 | } | |||
| 13450 | return SE.getZeroExtendExpr(Operand, Expr->getType()); | |||
| 13451 | } | |||
| 13452 | ||||
| 13453 | const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) { | |||
| 13454 | const SCEV *Operand = visit(Expr->getOperand()); | |||
| 13455 | const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Operand); | |||
| 13456 | if (AR && AR->getLoop() == L && AR->isAffine()) { | |||
| 13457 | // This couldn't be folded because the operand didn't have the nsw | |||
| 13458 | // flag. Add the nssw flag as an assumption that we could make. | |||
| 13459 | const SCEV *Step = AR->getStepRecurrence(SE); | |||
| 13460 | Type *Ty = Expr->getType(); | |||
| 13461 | if (addOverflowAssumption(AR, SCEVWrapPredicate::IncrementNSSW)) | |||
| 13462 | return SE.getAddRecExpr(SE.getSignExtendExpr(AR->getStart(), Ty), | |||
| 13463 | SE.getSignExtendExpr(Step, Ty), L, | |||
| 13464 | AR->getNoWrapFlags()); | |||
| 13465 | } | |||
| 13466 | return SE.getSignExtendExpr(Operand, Expr->getType()); | |||
| 13467 | } | |||
| 13468 | ||||
| 13469 | private: | |||
| 13470 | explicit SCEVPredicateRewriter(const Loop *L, ScalarEvolution &SE, | |||
| 13471 | SmallPtrSetImpl<const SCEVPredicate *> *NewPreds, | |||
| 13472 | SCEVUnionPredicate *Pred) | |||
| 13473 | : SCEVRewriteVisitor(SE), NewPreds(NewPreds), Pred(Pred), L(L) {} | |||
| 13474 | ||||
| 13475 | bool addOverflowAssumption(const SCEVPredicate *P) { | |||
| 13476 | if (!NewPreds) { | |||
| 13477 | // Check if we've already made this assumption. | |||
| 13478 | return Pred && Pred->implies(P); | |||
| 13479 | } | |||
| 13480 | NewPreds->insert(P); | |||
| 13481 | return true; | |||
| 13482 | } | |||
| 13483 | ||||
| 13484 | bool addOverflowAssumption(const SCEVAddRecExpr *AR, | |||
| 13485 | SCEVWrapPredicate::IncrementWrapFlags AddedFlags) { | |||
| 13486 | auto *A = SE.getWrapPredicate(AR, AddedFlags); | |||
| 13487 | return addOverflowAssumption(A); | |||
| 13488 | } | |||
| 13489 | ||||
| 13490 | // If \p Expr represents a PHINode, we try to see if it can be represented | |||
| 13491 | // as an AddRec, possibly under a predicate (PHISCEVPred). If it is possible | |||
| 13492 | // to add this predicate as a runtime overflow check, we return the AddRec. | |||
| 13493 | // If \p Expr does not meet these conditions (is not a PHI node, or we | |||
| 13494 | // couldn't create an AddRec for it, or couldn't add the predicate), we just | |||
| 13495 | // return \p Expr. | |||
| 13496 | const SCEV *convertToAddRecWithPreds(const SCEVUnknown *Expr) { | |||
| 13497 | if (!isa<PHINode>(Expr->getValue())) | |||
| 13498 | return Expr; | |||
| 13499 | Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>> | |||
| 13500 | PredicatedRewrite = SE.createAddRecFromPHIWithCasts(Expr); | |||
| 13501 | if (!PredicatedRewrite) | |||
| 13502 | return Expr; | |||
| 13503 | for (auto *P : PredicatedRewrite->second){ | |||
| 13504 | // Wrap predicates from outer loops are not supported. | |||
| 13505 | if (auto *WP = dyn_cast<const SCEVWrapPredicate>(P)) { | |||
| 13506 | auto *AR = cast<const SCEVAddRecExpr>(WP->getExpr()); | |||
| 13507 | if (L != AR->getLoop()) | |||
| 13508 | return Expr; | |||
| 13509 | } | |||
| 13510 | if (!addOverflowAssumption(P)) | |||
| 13511 | return Expr; | |||
| 13512 | } | |||
| 13513 | return PredicatedRewrite->first; | |||
| 13514 | } | |||
| 13515 | ||||
| 13516 | SmallPtrSetImpl<const SCEVPredicate *> *NewPreds; | |||
| 13517 | SCEVUnionPredicate *Pred; | |||
| 13518 | const Loop *L; | |||
| 13519 | }; | |||
| 13520 | ||||
| 13521 | } // end anonymous namespace | |||
| 13522 | ||||
| 13523 | const SCEV *ScalarEvolution::rewriteUsingPredicate(const SCEV *S, const Loop *L, | |||
| 13524 | SCEVUnionPredicate &Preds) { | |||
| 13525 | return SCEVPredicateRewriter::rewrite(S, L, *this, nullptr, &Preds); | |||
| 13526 | } | |||
| 13527 | ||||
| 13528 | const SCEVAddRecExpr *ScalarEvolution::convertSCEVToAddRecWithPredicates( | |||
| 13529 | const SCEV *S, const Loop *L, | |||
| 13530 | SmallPtrSetImpl<const SCEVPredicate *> &Preds) { | |||
| 13531 | SmallPtrSet<const SCEVPredicate *, 4> TransformPreds; | |||
| 13532 | S = SCEVPredicateRewriter::rewrite(S, L, *this, &TransformPreds, nullptr); | |||
| 13533 | auto *AddRec = dyn_cast<SCEVAddRecExpr>(S); | |||
| 13534 | ||||
| 13535 | if (!AddRec) | |||
| 13536 | return nullptr; | |||
| 13537 | ||||
| 13538 | // Since the transformation was successful, we can now transfer the SCEV | |||
| 13539 | // predicates. | |||
| 13540 | for (auto *P : TransformPreds) | |||
| 13541 | Preds.insert(P); | |||
| 13542 | ||||
| 13543 | return AddRec; | |||
| 13544 | } | |||
| 13545 | ||||
| 13546 | /// SCEV predicates | |||
| 13547 | SCEVPredicate::SCEVPredicate(const FoldingSetNodeIDRef ID, | |||
| 13548 | SCEVPredicateKind Kind) | |||
| 13549 | : FastID(ID), Kind(Kind) {} | |||
| 13550 | ||||
| 13551 | SCEVEqualPredicate::SCEVEqualPredicate(const FoldingSetNodeIDRef ID, | |||
| 13552 | const SCEV *LHS, const SCEV *RHS) | |||
| 13553 | : SCEVPredicate(ID, P_Equal), LHS(LHS), RHS(RHS) { | |||
| 13554 | assert(LHS->getType() == RHS->getType() && "LHS and RHS types don't match")((void)0); | |||
| 13555 | assert(LHS != RHS && "LHS and RHS are the same SCEV")((void)0); | |||
| 13556 | } | |||
| 13557 | ||||
| 13558 | bool SCEVEqualPredicate::implies(const SCEVPredicate *N) const { | |||
| 13559 | const auto *Op = dyn_cast<SCEVEqualPredicate>(N); | |||
| 13560 | ||||
| 13561 | if (!Op) | |||
| 13562 | return false; | |||
| 13563 | ||||
| 13564 | return Op->LHS == LHS && Op->RHS == RHS; | |||
| 13565 | } | |||
| 13566 | ||||
| 13567 | bool SCEVEqualPredicate::isAlwaysTrue() const { return false; } | |||
| 13568 | ||||
| 13569 | const SCEV *SCEVEqualPredicate::getExpr() const { return LHS; } | |||
| 13570 | ||||
| 13571 | void SCEVEqualPredicate::print(raw_ostream &OS, unsigned Depth) const { | |||
| 13572 | OS.indent(Depth) << "Equal predicate: " << *LHS << " == " << *RHS << "\n"; | |||
| 13573 | } | |||
| 13574 | ||||
| 13575 | SCEVWrapPredicate::SCEVWrapPredicate(const FoldingSetNodeIDRef ID, | |||
| 13576 | const SCEVAddRecExpr *AR, | |||
| 13577 | IncrementWrapFlags Flags) | |||
| 13578 | : SCEVPredicate(ID, P_Wrap), AR(AR), Flags(Flags) {} | |||
| 13579 | ||||
| 13580 | const SCEV *SCEVWrapPredicate::getExpr() const { return AR; } | |||
| 13581 | ||||
| 13582 | bool SCEVWrapPredicate::implies(const SCEVPredicate *N) const { | |||
| 13583 | const auto *Op = dyn_cast<SCEVWrapPredicate>(N); | |||
| 13584 | ||||
| 13585 | return Op && Op->AR == AR && setFlags(Flags, Op->Flags) == Flags; | |||
| 13586 | } | |||
| 13587 | ||||
| 13588 | bool SCEVWrapPredicate::isAlwaysTrue() const { | |||
| 13589 | SCEV::NoWrapFlags ScevFlags = AR->getNoWrapFlags(); | |||
| 13590 | IncrementWrapFlags IFlags = Flags; | |||
| 13591 | ||||
| 13592 | if (ScalarEvolution::setFlags(ScevFlags, SCEV::FlagNSW) == ScevFlags) | |||
| 13593 | IFlags = clearFlags(IFlags, IncrementNSSW); | |||
| 13594 | ||||
| 13595 | return IFlags == IncrementAnyWrap; | |||
| 13596 | } | |||
| 13597 | ||||
| 13598 | void SCEVWrapPredicate::print(raw_ostream &OS, unsigned Depth) const { | |||
| 13599 | OS.indent(Depth) << *getExpr() << " Added Flags: "; | |||
| 13600 | if (SCEVWrapPredicate::IncrementNUSW & getFlags()) | |||
| 13601 | OS << "<nusw>"; | |||
| 13602 | if (SCEVWrapPredicate::IncrementNSSW & getFlags()) | |||
| 13603 | OS << "<nssw>"; | |||
| 13604 | OS << "\n"; | |||
| 13605 | } | |||
| 13606 | ||||
| 13607 | SCEVWrapPredicate::IncrementWrapFlags | |||
| 13608 | SCEVWrapPredicate::getImpliedFlags(const SCEVAddRecExpr *AR, | |||
| 13609 | ScalarEvolution &SE) { | |||
| 13610 | IncrementWrapFlags ImpliedFlags = IncrementAnyWrap; | |||
| 13611 | SCEV::NoWrapFlags StaticFlags = AR->getNoWrapFlags(); | |||
| 13612 | ||||
| 13613 | // We can safely transfer the NSW flag as NSSW. | |||
| 13614 | if (ScalarEvolution::setFlags(StaticFlags, SCEV::FlagNSW) == StaticFlags) | |||
| 13615 | ImpliedFlags = IncrementNSSW; | |||
| 13616 | ||||
| 13617 | if (ScalarEvolution::setFlags(StaticFlags, SCEV::FlagNUW) == StaticFlags) { | |||
| 13618 | // If the increment is positive, the SCEV NUW flag will also imply the | |||
| 13619 | // WrapPredicate NUSW flag. | |||
| 13620 | if (const auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(SE))) | |||
| 13621 | if (Step->getValue()->getValue().isNonNegative()) | |||
| 13622 | ImpliedFlags = setFlags(ImpliedFlags, IncrementNUSW); | |||
| 13623 | } | |||
| 13624 | ||||
| 13625 | return ImpliedFlags; | |||
| 13626 | } | |||
| 13627 | ||||
| 13628 | /// Union predicates don't get cached so create a dummy set ID for it. | |||
| 13629 | SCEVUnionPredicate::SCEVUnionPredicate() | |||
| 13630 | : SCEVPredicate(FoldingSetNodeIDRef(nullptr, 0), P_Union) {} | |||
| 13631 | ||||
| 13632 | bool SCEVUnionPredicate::isAlwaysTrue() const { | |||
| 13633 | return all_of(Preds, | |||
| 13634 | [](const SCEVPredicate *I) { return I->isAlwaysTrue(); }); | |||
| 13635 | } | |||
| 13636 | ||||
| 13637 | ArrayRef<const SCEVPredicate *> | |||
| 13638 | SCEVUnionPredicate::getPredicatesForExpr(const SCEV *Expr) { | |||
| 13639 | auto I = SCEVToPreds.find(Expr); | |||
| 13640 | if (I == SCEVToPreds.end()) | |||
| 13641 | return ArrayRef<const SCEVPredicate *>(); | |||
| 13642 | return I->second; | |||
| 13643 | } | |||
| 13644 | ||||
| 13645 | bool SCEVUnionPredicate::implies(const SCEVPredicate *N) const { | |||
| 13646 | if (const auto *Set = dyn_cast<SCEVUnionPredicate>(N)) | |||
| 13647 | return all_of(Set->Preds, | |||
| 13648 | [this](const SCEVPredicate *I) { return this->implies(I); }); | |||
| 13649 | ||||
| 13650 | auto ScevPredsIt = SCEVToPreds.find(N->getExpr()); | |||
| 13651 | if (ScevPredsIt == SCEVToPreds.end()) | |||
| 13652 | return false; | |||
| 13653 | auto &SCEVPreds = ScevPredsIt->second; | |||
| 13654 | ||||
| 13655 | return any_of(SCEVPreds, | |||
| 13656 | [N](const SCEVPredicate *I) { return I->implies(N); }); | |||
| 13657 | } | |||
| 13658 | ||||
| 13659 | const SCEV *SCEVUnionPredicate::getExpr() const { return nullptr; } | |||
| 13660 | ||||
| 13661 | void SCEVUnionPredicate::print(raw_ostream &OS, unsigned Depth) const { | |||
| 13662 | for (auto Pred : Preds) | |||
| 13663 | Pred->print(OS, Depth); | |||
| 13664 | } | |||
| 13665 | ||||
| 13666 | void SCEVUnionPredicate::add(const SCEVPredicate *N) { | |||
| 13667 | if (const auto *Set = dyn_cast<SCEVUnionPredicate>(N)) { | |||
| 13668 | for (auto Pred : Set->Preds) | |||
| 13669 | add(Pred); | |||
| 13670 | return; | |||
| 13671 | } | |||
| 13672 | ||||
| 13673 | if (implies(N)) | |||
| 13674 | return; | |||
| 13675 | ||||
| 13676 | const SCEV *Key = N->getExpr(); | |||
| 13677 | assert(Key && "Only SCEVUnionPredicate doesn't have an "((void)0) | |||
| 13678 | " associated expression!")((void)0); | |||
| 13679 | ||||
| 13680 | SCEVToPreds[Key].push_back(N); | |||
| 13681 | Preds.push_back(N); | |||
| 13682 | } | |||
| 13683 | ||||
| 13684 | PredicatedScalarEvolution::PredicatedScalarEvolution(ScalarEvolution &SE, | |||
| 13685 | Loop &L) | |||
| 13686 | : SE(SE), L(L) {} | |||
| 13687 | ||||
| 13688 | const SCEV *PredicatedScalarEvolution::getSCEV(Value *V) { | |||
| 13689 | const SCEV *Expr = SE.getSCEV(V); | |||
| 13690 | RewriteEntry &Entry = RewriteMap[Expr]; | |||
| 13691 | ||||
| 13692 | // If we already have an entry and the version matches, return it. | |||
| 13693 | if (Entry.second && Generation == Entry.first) | |||
| 13694 | return Entry.second; | |||
| 13695 | ||||
| 13696 | // We found an entry but it's stale. Rewrite the stale entry | |||
| 13697 | // according to the current predicate. | |||
| 13698 | if (Entry.second) | |||
| 13699 | Expr = Entry.second; | |||
| 13700 | ||||
| 13701 | const SCEV *NewSCEV = SE.rewriteUsingPredicate(Expr, &L, Preds); | |||
| 13702 | Entry = {Generation, NewSCEV}; | |||
| 13703 | ||||
| 13704 | return NewSCEV; | |||
| 13705 | } | |||
| 13706 | ||||
| 13707 | const SCEV *PredicatedScalarEvolution::getBackedgeTakenCount() { | |||
| 13708 | if (!BackedgeCount) { | |||
| ||||
| 13709 | SCEVUnionPredicate BackedgePred; | |||
| 13710 | BackedgeCount = SE.getPredicatedBackedgeTakenCount(&L, BackedgePred); | |||
| 13711 | addPredicate(BackedgePred); | |||
| 13712 | } | |||
| 13713 | return BackedgeCount; | |||
| 13714 | } | |||
| 13715 | ||||
| 13716 | void PredicatedScalarEvolution::addPredicate(const SCEVPredicate &Pred) { | |||
| 13717 | if (Preds.implies(&Pred)) | |||
| 13718 | return; | |||
| 13719 | Preds.add(&Pred); | |||
| 13720 | updateGeneration(); | |||
| 13721 | } | |||
| 13722 | ||||
| 13723 | const SCEVUnionPredicate &PredicatedScalarEvolution::getUnionPredicate() const { | |||
| 13724 | return Preds; | |||
| 13725 | } | |||
| 13726 | ||||
| 13727 | void PredicatedScalarEvolution::updateGeneration() { | |||
| 13728 | // If the generation number wrapped recompute everything. | |||
| 13729 | if (++Generation == 0) { | |||
| 13730 | for (auto &II : RewriteMap) { | |||
| 13731 | const SCEV *Rewritten = II.second.second; | |||
| 13732 | II.second = {Generation, SE.rewriteUsingPredicate(Rewritten, &L, Preds)}; | |||
| 13733 | } | |||
| 13734 | } | |||
| 13735 | } | |||
| 13736 | ||||
| 13737 | void PredicatedScalarEvolution::setNoOverflow( | |||
| 13738 | Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags) { | |||
| 13739 | const SCEV *Expr = getSCEV(V); | |||
| 13740 | const auto *AR = cast<SCEVAddRecExpr>(Expr); | |||
| 13741 | ||||
| 13742 | auto ImpliedFlags = SCEVWrapPredicate::getImpliedFlags(AR, SE); | |||
| 13743 | ||||
| 13744 | // Clear the statically implied flags. | |||
| 13745 | Flags = SCEVWrapPredicate::clearFlags(Flags, ImpliedFlags); | |||
| 13746 | addPredicate(*SE.getWrapPredicate(AR, Flags)); | |||
| 13747 | ||||
| 13748 | auto II = FlagsMap.insert({V, Flags}); | |||
| 13749 | if (!II.second) | |||
| 13750 | II.first->second = SCEVWrapPredicate::setFlags(Flags, II.first->second); | |||
| 13751 | } | |||
| 13752 | ||||
| 13753 | bool PredicatedScalarEvolution::hasNoOverflow( | |||
| 13754 | Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags) { | |||
| 13755 | const SCEV *Expr = getSCEV(V); | |||
| 13756 | const auto *AR = cast<SCEVAddRecExpr>(Expr); | |||
| 13757 | ||||
| 13758 | Flags = SCEVWrapPredicate::clearFlags( | |||
| 13759 | Flags, SCEVWrapPredicate::getImpliedFlags(AR, SE)); | |||
| 13760 | ||||
| 13761 | auto II = FlagsMap.find(V); | |||
| 13762 | ||||
| 13763 | if (II != FlagsMap.end()) | |||
| 13764 | Flags = SCEVWrapPredicate::clearFlags(Flags, II->second); | |||
| 13765 | ||||
| 13766 | return Flags == SCEVWrapPredicate::IncrementAnyWrap; | |||
| 13767 | } | |||
| 13768 | ||||
| 13769 | const SCEVAddRecExpr *PredicatedScalarEvolution::getAsAddRec(Value *V) { | |||
| 13770 | const SCEV *Expr = this->getSCEV(V); | |||
| 13771 | SmallPtrSet<const SCEVPredicate *, 4> NewPreds; | |||
| 13772 | auto *New = SE.convertSCEVToAddRecWithPredicates(Expr, &L, NewPreds); | |||
| 13773 | ||||
| 13774 | if (!New) | |||
| 13775 | return nullptr; | |||
| 13776 | ||||
| 13777 | for (auto *P : NewPreds) | |||
| 13778 | Preds.add(P); | |||
| 13779 | ||||
| 13780 | updateGeneration(); | |||
| 13781 | RewriteMap[SE.getSCEV(V)] = {Generation, New}; | |||
| 13782 | return New; | |||
| 13783 | } | |||
| 13784 | ||||
| 13785 | PredicatedScalarEvolution::PredicatedScalarEvolution( | |||
| 13786 | const PredicatedScalarEvolution &Init) | |||
| 13787 | : RewriteMap(Init.RewriteMap), SE(Init.SE), L(Init.L), Preds(Init.Preds), | |||
| 13788 | Generation(Init.Generation), BackedgeCount(Init.BackedgeCount) { | |||
| 13789 | for (auto I : Init.FlagsMap) | |||
| 13790 | FlagsMap.insert(I); | |||
| 13791 | } | |||
| 13792 | ||||
| 13793 | void PredicatedScalarEvolution::print(raw_ostream &OS, unsigned Depth) const { | |||
| 13794 | // For each block. | |||
| 13795 | for (auto *BB : L.getBlocks()) | |||
| 13796 | for (auto &I : *BB) { | |||
| 13797 | if (!SE.isSCEVable(I.getType())) | |||
| 13798 | continue; | |||
| 13799 | ||||
| 13800 | auto *Expr = SE.getSCEV(&I); | |||
| 13801 | auto II = RewriteMap.find(Expr); | |||
| 13802 | ||||
| 13803 | if (II == RewriteMap.end()) | |||
| 13804 | continue; | |||
| 13805 | ||||
| 13806 | // Don't print things that are not interesting. | |||
| 13807 | if (II->second.second == Expr) | |||
| 13808 | continue; | |||
| 13809 | ||||
| 13810 | OS.indent(Depth) << "[PSE]" << I << ":\n"; | |||
| 13811 | OS.indent(Depth + 2) << *Expr << "\n"; | |||
| 13812 | OS.indent(Depth + 2) << "--> " << *II->second.second << "\n"; | |||
| 13813 | } | |||
| 13814 | } | |||
| 13815 | ||||
| 13816 | // Match the mathematical pattern A - (A / B) * B, where A and B can be | |||
| 13817 | // arbitrary expressions. Also match zext (trunc A to iB) to iY, which is used | |||
| 13818 | // for URem with constant power-of-2 second operands. | |||
| 13819 | // It's not always easy, as A and B can be folded (imagine A is X / 2, and B is | |||
| 13820 | // 4, A / B becomes X / 8). | |||
| 13821 | bool ScalarEvolution::matchURem(const SCEV *Expr, const SCEV *&LHS, | |||
| 13822 | const SCEV *&RHS) { | |||
| 13823 | // Try to match 'zext (trunc A to iB) to iY', which is used | |||
| 13824 | // for URem with constant power-of-2 second operands. Make sure the size of | |||
| 13825 | // the operand A matches the size of the whole expressions. | |||
| 13826 | if (const auto *ZExt = dyn_cast<SCEVZeroExtendExpr>(Expr)) | |||
| 13827 | if (const auto *Trunc = dyn_cast<SCEVTruncateExpr>(ZExt->getOperand(0))) { | |||
| 13828 | LHS = Trunc->getOperand(); | |||
| 13829 | // Bail out if the type of the LHS is larger than the type of the | |||
| 13830 | // expression for now. | |||
| 13831 | if (getTypeSizeInBits(LHS->getType()) > | |||
| 13832 | getTypeSizeInBits(Expr->getType())) | |||
| 13833 | return false; | |||
| 13834 | if (LHS->getType() != Expr->getType()) | |||
| 13835 | LHS = getZeroExtendExpr(LHS, Expr->getType()); | |||
| 13836 | RHS = getConstant(APInt(getTypeSizeInBits(Expr->getType()), 1) | |||
| 13837 | << getTypeSizeInBits(Trunc->getType())); | |||
| 13838 | return true; | |||
| 13839 | } | |||
| 13840 | const auto *Add = dyn_cast<SCEVAddExpr>(Expr); | |||
| 13841 | if (Add == nullptr || Add->getNumOperands() != 2) | |||
| 13842 | return false; | |||
| 13843 | ||||
| 13844 | const SCEV *A = Add->getOperand(1); | |||
| 13845 | const auto *Mul = dyn_cast<SCEVMulExpr>(Add->getOperand(0)); | |||
| 13846 | ||||
| 13847 | if (Mul == nullptr) | |||
| 13848 | return false; | |||
| 13849 | ||||
| 13850 | const auto MatchURemWithDivisor = [&](const SCEV *B) { | |||
| 13851 | // (SomeExpr + (-(SomeExpr / B) * B)). | |||
| 13852 | if (Expr == getURemExpr(A, B)) { | |||
| 13853 | LHS = A; | |||
| 13854 | RHS = B; | |||
| 13855 | return true; | |||
| 13856 | } | |||
| 13857 | return false; | |||
| 13858 | }; | |||
| 13859 | ||||
| 13860 | // (SomeExpr + (-1 * (SomeExpr / B) * B)). | |||
| 13861 | if (Mul->getNumOperands() == 3 && isa<SCEVConstant>(Mul->getOperand(0))) | |||
| 13862 | return MatchURemWithDivisor(Mul->getOperand(1)) || | |||
| 13863 | MatchURemWithDivisor(Mul->getOperand(2)); | |||
| 13864 | ||||
| 13865 | // (SomeExpr + ((-SomeExpr / B) * B)) or (SomeExpr + ((SomeExpr / B) * -B)). | |||
| 13866 | if (Mul->getNumOperands() == 2) | |||
| 13867 | return MatchURemWithDivisor(Mul->getOperand(1)) || | |||
| 13868 | MatchURemWithDivisor(Mul->getOperand(0)) || | |||
| 13869 | MatchURemWithDivisor(getNegativeSCEV(Mul->getOperand(1))) || | |||
| 13870 | MatchURemWithDivisor(getNegativeSCEV(Mul->getOperand(0))); | |||
| 13871 | return false; | |||
| 13872 | } | |||
| 13873 | ||||
| 13874 | const SCEV * | |||
| 13875 | ScalarEvolution::computeSymbolicMaxBackedgeTakenCount(const Loop *L) { | |||
| 13876 | SmallVector<BasicBlock*, 16> ExitingBlocks; | |||
| 13877 | L->getExitingBlocks(ExitingBlocks); | |||
| 13878 | ||||
| 13879 | // Form an expression for the maximum exit count possible for this loop. We | |||
| 13880 | // merge the max and exact information to approximate a version of | |||
| 13881 | // getConstantMaxBackedgeTakenCount which isn't restricted to just constants. | |||
| 13882 | SmallVector<const SCEV*, 4> ExitCounts; | |||
| 13883 | for (BasicBlock *ExitingBB : ExitingBlocks) { | |||
| 13884 | const SCEV *ExitCount = getExitCount(L, ExitingBB); | |||
| 13885 | if (isa<SCEVCouldNotCompute>(ExitCount)) | |||
| 13886 | ExitCount = getExitCount(L, ExitingBB, | |||
| 13887 | ScalarEvolution::ConstantMaximum); | |||
| 13888 | if (!isa<SCEVCouldNotCompute>(ExitCount)) { | |||
| 13889 | assert(DT.dominates(ExitingBB, L->getLoopLatch()) &&((void)0) | |||
| 13890 | "We should only have known counts for exiting blocks that "((void)0) | |||
| 13891 | "dominate latch!")((void)0); | |||
| 13892 | ExitCounts.push_back(ExitCount); | |||
| 13893 | } | |||
| 13894 | } | |||
| 13895 | if (ExitCounts.empty()) | |||
| 13896 | return getCouldNotCompute(); | |||
| 13897 | return getUMinFromMismatchedTypes(ExitCounts); | |||
| 13898 | } | |||
| 13899 | ||||
| 13900 | /// This rewriter is similar to SCEVParameterRewriter (it replaces SCEVUnknown | |||
| 13901 | /// components following the Map (Value -> SCEV)), but skips AddRecExpr because | |||
| 13902 | /// we cannot guarantee that the replacement is loop invariant in the loop of | |||
| 13903 | /// the AddRec. | |||
| 13904 | class SCEVLoopGuardRewriter : public SCEVRewriteVisitor<SCEVLoopGuardRewriter> { | |||
| 13905 | ValueToSCEVMapTy ⤅ | |||
| 13906 | ||||
| 13907 | public: | |||
| 13908 | SCEVLoopGuardRewriter(ScalarEvolution &SE, ValueToSCEVMapTy &M) | |||
| 13909 | : SCEVRewriteVisitor(SE), Map(M) {} | |||
| 13910 | ||||
| 13911 | const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { return Expr; } | |||
| 13912 | ||||
| 13913 | const SCEV *visitUnknown(const SCEVUnknown *Expr) { | |||
| 13914 | auto I = Map.find(Expr->getValue()); | |||
| 13915 | if (I == Map.end()) | |||
| 13916 | return Expr; | |||
| 13917 | return I->second; | |||
| 13918 | } | |||
| 13919 | }; | |||
| 13920 | ||||
| 13921 | const SCEV *ScalarEvolution::applyLoopGuards(const SCEV *Expr, const Loop *L) { | |||
| 13922 | auto CollectCondition = [&](ICmpInst::Predicate Predicate, const SCEV *LHS, | |||
| 13923 | const SCEV *RHS, ValueToSCEVMapTy &RewriteMap) { | |||
| 13924 | // If we have LHS == 0, check if LHS is computing a property of some unknown | |||
| 13925 | // SCEV %v which we can rewrite %v to express explicitly. | |||
| 13926 | const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS); | |||
| 13927 | if (Predicate == CmpInst::ICMP_EQ && RHSC && | |||
| 13928 | RHSC->getValue()->isNullValue()) { | |||
| 13929 | // If LHS is A % B, i.e. A % B == 0, rewrite A to (A /u B) * B to | |||
| 13930 | // explicitly express that. | |||
| 13931 | const SCEV *URemLHS = nullptr; | |||
| 13932 | const SCEV *URemRHS = nullptr; | |||
| 13933 | if (matchURem(LHS, URemLHS, URemRHS)) { | |||
| 13934 | if (const SCEVUnknown *LHSUnknown = dyn_cast<SCEVUnknown>(URemLHS)) { | |||
| 13935 | Value *V = LHSUnknown->getValue(); | |||
| 13936 | auto Multiple = | |||
| 13937 | getMulExpr(getUDivExpr(URemLHS, URemRHS), URemRHS, | |||
| 13938 | (SCEV::NoWrapFlags)(SCEV::FlagNUW | SCEV::FlagNSW)); | |||
| 13939 | RewriteMap[V] = Multiple; | |||
| 13940 | return; | |||
| 13941 | } | |||
| 13942 | } | |||
| 13943 | } | |||
| 13944 | ||||
| 13945 | if (!isa<SCEVUnknown>(LHS) && isa<SCEVUnknown>(RHS)) { | |||
| 13946 | std::swap(LHS, RHS); | |||
| 13947 | Predicate = CmpInst::getSwappedPredicate(Predicate); | |||
| 13948 | } | |||
| 13949 | ||||
| 13950 | // Check for a condition of the form (-C1 + X < C2). InstCombine will | |||
| 13951 | // create this form when combining two checks of the form (X u< C2 + C1) and | |||
| 13952 | // (X >=u C1). | |||
| 13953 | auto MatchRangeCheckIdiom = [this, Predicate, LHS, RHS, &RewriteMap]() { | |||
| 13954 | auto *AddExpr = dyn_cast<SCEVAddExpr>(LHS); | |||
| 13955 | if (!AddExpr || AddExpr->getNumOperands() != 2) | |||
| 13956 | return false; | |||
| 13957 | ||||
| 13958 | auto *C1 = dyn_cast<SCEVConstant>(AddExpr->getOperand(0)); | |||
| 13959 | auto *LHSUnknown = dyn_cast<SCEVUnknown>(AddExpr->getOperand(1)); | |||
| 13960 | auto *C2 = dyn_cast<SCEVConstant>(RHS); | |||
| 13961 | if (!C1 || !C2 || !LHSUnknown) | |||
| 13962 | return false; | |||
| 13963 | ||||
| 13964 | auto ExactRegion = | |||
| 13965 | ConstantRange::makeExactICmpRegion(Predicate, C2->getAPInt()) | |||
| 13966 | .sub(C1->getAPInt()); | |||
| 13967 | ||||
| 13968 | // Bail out, unless we have a non-wrapping, monotonic range. | |||
| 13969 | if (ExactRegion.isWrappedSet() || ExactRegion.isFullSet()) | |||
| 13970 | return false; | |||
| 13971 | auto I = RewriteMap.find(LHSUnknown->getValue()); | |||
| 13972 | const SCEV *RewrittenLHS = I != RewriteMap.end() ? I->second : LHSUnknown; | |||
| 13973 | RewriteMap[LHSUnknown->getValue()] = getUMaxExpr( | |||
| 13974 | getConstant(ExactRegion.getUnsignedMin()), | |||
| 13975 | getUMinExpr(RewrittenLHS, getConstant(ExactRegion.getUnsignedMax()))); | |||
| 13976 | return true; | |||
| 13977 | }; | |||
| 13978 | if (MatchRangeCheckIdiom()) | |||
| 13979 | return; | |||
| 13980 | ||||
| 13981 | // For now, limit to conditions that provide information about unknown | |||
| 13982 | // expressions. RHS also cannot contain add recurrences. | |||
| 13983 | auto *LHSUnknown = dyn_cast<SCEVUnknown>(LHS); | |||
| 13984 | if (!LHSUnknown || containsAddRecurrence(RHS)) | |||
| 13985 | return; | |||
| 13986 | ||||
| 13987 | // Check whether LHS has already been rewritten. In that case we want to | |||
| 13988 | // chain further rewrites onto the already rewritten value. | |||
| 13989 | auto I = RewriteMap.find(LHSUnknown->getValue()); | |||
| 13990 | const SCEV *RewrittenLHS = I != RewriteMap.end() ? I->second : LHS; | |||
| 13991 | const SCEV *RewrittenRHS = nullptr; | |||
| 13992 | switch (Predicate) { | |||
| 13993 | case CmpInst::ICMP_ULT: | |||
| 13994 | RewrittenRHS = | |||
| 13995 | getUMinExpr(RewrittenLHS, getMinusSCEV(RHS, getOne(RHS->getType()))); | |||
| 13996 | break; | |||
| 13997 | case CmpInst::ICMP_SLT: | |||
| 13998 | RewrittenRHS = | |||
| 13999 | getSMinExpr(RewrittenLHS, getMinusSCEV(RHS, getOne(RHS->getType()))); | |||
| 14000 | break; | |||
| 14001 | case CmpInst::ICMP_ULE: | |||
| 14002 | RewrittenRHS = getUMinExpr(RewrittenLHS, RHS); | |||
| 14003 | break; | |||
| 14004 | case CmpInst::ICMP_SLE: | |||
| 14005 | RewrittenRHS = getSMinExpr(RewrittenLHS, RHS); | |||
| 14006 | break; | |||
| 14007 | case CmpInst::ICMP_UGT: | |||
| 14008 | RewrittenRHS = | |||
| 14009 | getUMaxExpr(RewrittenLHS, getAddExpr(RHS, getOne(RHS->getType()))); | |||
| 14010 | break; | |||
| 14011 | case CmpInst::ICMP_SGT: | |||
| 14012 | RewrittenRHS = | |||
| 14013 | getSMaxExpr(RewrittenLHS, getAddExpr(RHS, getOne(RHS->getType()))); | |||
| 14014 | break; | |||
| 14015 | case CmpInst::ICMP_UGE: | |||
| 14016 | RewrittenRHS = getUMaxExpr(RewrittenLHS, RHS); | |||
| 14017 | break; | |||
| 14018 | case CmpInst::ICMP_SGE: | |||
| 14019 | RewrittenRHS = getSMaxExpr(RewrittenLHS, RHS); | |||
| 14020 | break; | |||
| 14021 | case CmpInst::ICMP_EQ: | |||
| 14022 | if (isa<SCEVConstant>(RHS)) | |||
| 14023 | RewrittenRHS = RHS; | |||
| 14024 | break; | |||
| 14025 | case CmpInst::ICMP_NE: | |||
| 14026 | if (isa<SCEVConstant>(RHS) && | |||
| 14027 | cast<SCEVConstant>(RHS)->getValue()->isNullValue()) | |||
| 14028 | RewrittenRHS = getUMaxExpr(RewrittenLHS, getOne(RHS->getType())); | |||
| 14029 | break; | |||
| 14030 | default: | |||
| 14031 | break; | |||
| 14032 | } | |||
| 14033 | ||||
| 14034 | if (RewrittenRHS) | |||
| 14035 | RewriteMap[LHSUnknown->getValue()] = RewrittenRHS; | |||
| 14036 | }; | |||
| 14037 | // Starting at the loop predecessor, climb up the predecessor chain, as long | |||
| 14038 | // as there are predecessors that can be found that have unique successors | |||
| 14039 | // leading to the original header. | |||
| 14040 | // TODO: share this logic with isLoopEntryGuardedByCond. | |||
| 14041 | ValueToSCEVMapTy RewriteMap; | |||
| 14042 | for (std::pair<const BasicBlock *, const BasicBlock *> Pair( | |||
| 14043 | L->getLoopPredecessor(), L->getHeader()); | |||
| 14044 | Pair.first; Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) { | |||
| 14045 | ||||
| 14046 | const BranchInst *LoopEntryPredicate = | |||
| 14047 | dyn_cast<BranchInst>(Pair.first->getTerminator()); | |||
| 14048 | if (!LoopEntryPredicate || LoopEntryPredicate->isUnconditional()) | |||
| 14049 | continue; | |||
| 14050 | ||||
| 14051 | bool EnterIfTrue = LoopEntryPredicate->getSuccessor(0) == Pair.second; | |||
| 14052 | SmallVector<Value *, 8> Worklist; | |||
| 14053 | SmallPtrSet<Value *, 8> Visited; | |||
| 14054 | Worklist.push_back(LoopEntryPredicate->getCondition()); | |||
| 14055 | while (!Worklist.empty()) { | |||
| 14056 | Value *Cond = Worklist.pop_back_val(); | |||
| 14057 | if (!Visited.insert(Cond).second) | |||
| 14058 | continue; | |||
| 14059 | ||||
| 14060 | if (auto *Cmp = dyn_cast<ICmpInst>(Cond)) { | |||
| 14061 | auto Predicate = | |||
| 14062 | EnterIfTrue ? Cmp->getPredicate() : Cmp->getInversePredicate(); | |||
| 14063 | CollectCondition(Predicate, getSCEV(Cmp->getOperand(0)), | |||
| 14064 | getSCEV(Cmp->getOperand(1)), RewriteMap); | |||
| 14065 | continue; | |||
| 14066 | } | |||
| 14067 | ||||
| 14068 | Value *L, *R; | |||
| 14069 | if (EnterIfTrue ? match(Cond, m_LogicalAnd(m_Value(L), m_Value(R))) | |||
| 14070 | : match(Cond, m_LogicalOr(m_Value(L), m_Value(R)))) { | |||
| 14071 | Worklist.push_back(L); | |||
| 14072 | Worklist.push_back(R); | |||
| 14073 | } | |||
| 14074 | } | |||
| 14075 | } | |||
| 14076 | ||||
| 14077 | // Also collect information from assumptions dominating the loop. | |||
| 14078 | for (auto &AssumeVH : AC.assumptions()) { | |||
| 14079 | if (!AssumeVH) | |||
| 14080 | continue; | |||
| 14081 | auto *AssumeI = cast<CallInst>(AssumeVH); | |||
| 14082 | auto *Cmp = dyn_cast<ICmpInst>(AssumeI->getOperand(0)); | |||
| 14083 | if (!Cmp || !DT.dominates(AssumeI, L->getHeader())) | |||
| 14084 | continue; | |||
| 14085 | CollectCondition(Cmp->getPredicate(), getSCEV(Cmp->getOperand(0)), | |||
| 14086 | getSCEV(Cmp->getOperand(1)), RewriteMap); | |||
| 14087 | } | |||
| 14088 | ||||
| 14089 | if (RewriteMap.empty()) | |||
| 14090 | return Expr; | |||
| 14091 | SCEVLoopGuardRewriter Rewriter(*this, RewriteMap); | |||
| 14092 | return Rewriter.visit(Expr); | |||
| 14093 | } |