| File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Analysis/ScalarEvolution.cpp |
| Warning: | line 10451, column 35 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: |