| File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/Scalar/LICM.cpp |
| Warning: | line 1173, column 22 Called C++ object pointer is null |
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| 1 | //===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===// | |||
| 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 pass performs loop invariant code motion, attempting to remove as much | |||
| 10 | // code from the body of a loop as possible. It does this by either hoisting | |||
| 11 | // code into the preheader block, or by sinking code to the exit blocks if it is | |||
| 12 | // safe. This pass also promotes must-aliased memory locations in the loop to | |||
| 13 | // live in registers, thus hoisting and sinking "invariant" loads and stores. | |||
| 14 | // | |||
| 15 | // Hoisting operations out of loops is a canonicalization transform. It | |||
| 16 | // enables and simplifies subsequent optimizations in the middle-end. | |||
| 17 | // Rematerialization of hoisted instructions to reduce register pressure is the | |||
| 18 | // responsibility of the back-end, which has more accurate information about | |||
| 19 | // register pressure and also handles other optimizations than LICM that | |||
| 20 | // increase live-ranges. | |||
| 21 | // | |||
| 22 | // This pass uses alias analysis for two purposes: | |||
| 23 | // | |||
| 24 | // 1. Moving loop invariant loads and calls out of loops. If we can determine | |||
| 25 | // that a load or call inside of a loop never aliases anything stored to, | |||
| 26 | // we can hoist it or sink it like any other instruction. | |||
| 27 | // 2. Scalar Promotion of Memory - If there is a store instruction inside of | |||
| 28 | // the loop, we try to move the store to happen AFTER the loop instead of | |||
| 29 | // inside of the loop. This can only happen if a few conditions are true: | |||
| 30 | // A. The pointer stored through is loop invariant | |||
| 31 | // B. There are no stores or loads in the loop which _may_ alias the | |||
| 32 | // pointer. There are no calls in the loop which mod/ref the pointer. | |||
| 33 | // If these conditions are true, we can promote the loads and stores in the | |||
| 34 | // loop of the pointer to use a temporary alloca'd variable. We then use | |||
| 35 | // the SSAUpdater to construct the appropriate SSA form for the value. | |||
| 36 | // | |||
| 37 | //===----------------------------------------------------------------------===// | |||
| 38 | ||||
| 39 | #include "llvm/Transforms/Scalar/LICM.h" | |||
| 40 | #include "llvm/ADT/SetOperations.h" | |||
| 41 | #include "llvm/ADT/Statistic.h" | |||
| 42 | #include "llvm/Analysis/AliasAnalysis.h" | |||
| 43 | #include "llvm/Analysis/AliasSetTracker.h" | |||
| 44 | #include "llvm/Analysis/BasicAliasAnalysis.h" | |||
| 45 | #include "llvm/Analysis/BlockFrequencyInfo.h" | |||
| 46 | #include "llvm/Analysis/CaptureTracking.h" | |||
| 47 | #include "llvm/Analysis/ConstantFolding.h" | |||
| 48 | #include "llvm/Analysis/GlobalsModRef.h" | |||
| 49 | #include "llvm/Analysis/GuardUtils.h" | |||
| 50 | #include "llvm/Analysis/LazyBlockFrequencyInfo.h" | |||
| 51 | #include "llvm/Analysis/Loads.h" | |||
| 52 | #include "llvm/Analysis/LoopInfo.h" | |||
| 53 | #include "llvm/Analysis/LoopIterator.h" | |||
| 54 | #include "llvm/Analysis/LoopPass.h" | |||
| 55 | #include "llvm/Analysis/MemoryBuiltins.h" | |||
| 56 | #include "llvm/Analysis/MemorySSA.h" | |||
| 57 | #include "llvm/Analysis/MemorySSAUpdater.h" | |||
| 58 | #include "llvm/Analysis/MustExecute.h" | |||
| 59 | #include "llvm/Analysis/OptimizationRemarkEmitter.h" | |||
| 60 | #include "llvm/Analysis/ScalarEvolution.h" | |||
| 61 | #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h" | |||
| 62 | #include "llvm/Analysis/TargetLibraryInfo.h" | |||
| 63 | #include "llvm/Analysis/ValueTracking.h" | |||
| 64 | #include "llvm/IR/CFG.h" | |||
| 65 | #include "llvm/IR/Constants.h" | |||
| 66 | #include "llvm/IR/DataLayout.h" | |||
| 67 | #include "llvm/IR/DebugInfoMetadata.h" | |||
| 68 | #include "llvm/IR/DerivedTypes.h" | |||
| 69 | #include "llvm/IR/Dominators.h" | |||
| 70 | #include "llvm/IR/Instructions.h" | |||
| 71 | #include "llvm/IR/IntrinsicInst.h" | |||
| 72 | #include "llvm/IR/LLVMContext.h" | |||
| 73 | #include "llvm/IR/Metadata.h" | |||
| 74 | #include "llvm/IR/PatternMatch.h" | |||
| 75 | #include "llvm/IR/PredIteratorCache.h" | |||
| 76 | #include "llvm/InitializePasses.h" | |||
| 77 | #include "llvm/Support/CommandLine.h" | |||
| 78 | #include "llvm/Support/Debug.h" | |||
| 79 | #include "llvm/Support/raw_ostream.h" | |||
| 80 | #include "llvm/Transforms/Scalar.h" | |||
| 81 | #include "llvm/Transforms/Scalar/LoopPassManager.h" | |||
| 82 | #include "llvm/Transforms/Utils/AssumeBundleBuilder.h" | |||
| 83 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | |||
| 84 | #include "llvm/Transforms/Utils/Local.h" | |||
| 85 | #include "llvm/Transforms/Utils/LoopUtils.h" | |||
| 86 | #include "llvm/Transforms/Utils/SSAUpdater.h" | |||
| 87 | #include <algorithm> | |||
| 88 | #include <utility> | |||
| 89 | using namespace llvm; | |||
| 90 | ||||
| 91 | #define DEBUG_TYPE"licm" "licm" | |||
| 92 | ||||
| 93 | STATISTIC(NumCreatedBlocks, "Number of blocks created")static llvm::Statistic NumCreatedBlocks = {"licm", "NumCreatedBlocks" , "Number of blocks created"}; | |||
| 94 | STATISTIC(NumClonedBranches, "Number of branches cloned")static llvm::Statistic NumClonedBranches = {"licm", "NumClonedBranches" , "Number of branches cloned"}; | |||
| 95 | STATISTIC(NumSunk, "Number of instructions sunk out of loop")static llvm::Statistic NumSunk = {"licm", "NumSunk", "Number of instructions sunk out of loop" }; | |||
| 96 | STATISTIC(NumHoisted, "Number of instructions hoisted out of loop")static llvm::Statistic NumHoisted = {"licm", "NumHoisted", "Number of instructions hoisted out of loop" }; | |||
| 97 | STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk")static llvm::Statistic NumMovedLoads = {"licm", "NumMovedLoads" , "Number of load insts hoisted or sunk"}; | |||
| 98 | STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk")static llvm::Statistic NumMovedCalls = {"licm", "NumMovedCalls" , "Number of call insts hoisted or sunk"}; | |||
| 99 | STATISTIC(NumPromoted, "Number of memory locations promoted to registers")static llvm::Statistic NumPromoted = {"licm", "NumPromoted", "Number of memory locations promoted to registers" }; | |||
| 100 | ||||
| 101 | /// Memory promotion is enabled by default. | |||
| 102 | static cl::opt<bool> | |||
| 103 | DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false), | |||
| 104 | cl::desc("Disable memory promotion in LICM pass")); | |||
| 105 | ||||
| 106 | static cl::opt<bool> ControlFlowHoisting( | |||
| 107 | "licm-control-flow-hoisting", cl::Hidden, cl::init(false), | |||
| 108 | cl::desc("Enable control flow (and PHI) hoisting in LICM")); | |||
| 109 | ||||
| 110 | static cl::opt<unsigned> HoistSinkColdnessThreshold( | |||
| 111 | "licm-coldness-threshold", cl::Hidden, cl::init(4), | |||
| 112 | cl::desc("Relative coldness Threshold of hoisting/sinking destination " | |||
| 113 | "block for LICM to be considered beneficial")); | |||
| 114 | ||||
| 115 | static cl::opt<uint32_t> MaxNumUsesTraversed( | |||
| 116 | "licm-max-num-uses-traversed", cl::Hidden, cl::init(8), | |||
| 117 | cl::desc("Max num uses visited for identifying load " | |||
| 118 | "invariance in loop using invariant start (default = 8)")); | |||
| 119 | ||||
| 120 | // Default value of zero implies we use the regular alias set tracker mechanism | |||
| 121 | // instead of the cross product using AA to identify aliasing of the memory | |||
| 122 | // location we are interested in. | |||
| 123 | static cl::opt<int> | |||
| 124 | LICMN2Theshold("licm-n2-threshold", cl::Hidden, cl::init(0), | |||
| 125 | cl::desc("How many instruction to cross product using AA")); | |||
| 126 | ||||
| 127 | // Experimental option to allow imprecision in LICM in pathological cases, in | |||
| 128 | // exchange for faster compile. This is to be removed if MemorySSA starts to | |||
| 129 | // address the same issue. This flag applies only when LICM uses MemorySSA | |||
| 130 | // instead on AliasSetTracker. LICM calls MemorySSAWalker's | |||
| 131 | // getClobberingMemoryAccess, up to the value of the Cap, getting perfect | |||
| 132 | // accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess, | |||
| 133 | // which may not be precise, since optimizeUses is capped. The result is | |||
| 134 | // correct, but we may not get as "far up" as possible to get which access is | |||
| 135 | // clobbering the one queried. | |||
| 136 | cl::opt<unsigned> llvm::SetLicmMssaOptCap( | |||
| 137 | "licm-mssa-optimization-cap", cl::init(100), cl::Hidden, | |||
| 138 | cl::desc("Enable imprecision in LICM in pathological cases, in exchange " | |||
| 139 | "for faster compile. Caps the MemorySSA clobbering calls.")); | |||
| 140 | ||||
| 141 | // Experimentally, memory promotion carries less importance than sinking and | |||
| 142 | // hoisting. Limit when we do promotion when using MemorySSA, in order to save | |||
| 143 | // compile time. | |||
| 144 | cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap( | |||
| 145 | "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden, | |||
| 146 | cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no " | |||
| 147 | "effect. When MSSA in LICM is enabled, then this is the maximum " | |||
| 148 | "number of accesses allowed to be present in a loop in order to " | |||
| 149 | "enable memory promotion.")); | |||
| 150 | ||||
| 151 | static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI); | |||
| 152 | static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 153 | const LoopSafetyInfo *SafetyInfo, | |||
| 154 | TargetTransformInfo *TTI, bool &FreeInLoop); | |||
| 155 | static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, | |||
| 156 | BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, | |||
| 157 | MemorySSAUpdater *MSSAU, ScalarEvolution *SE, | |||
| 158 | OptimizationRemarkEmitter *ORE); | |||
| 159 | static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, | |||
| 160 | BlockFrequencyInfo *BFI, const Loop *CurLoop, | |||
| 161 | ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU, | |||
| 162 | OptimizationRemarkEmitter *ORE); | |||
| 163 | static bool isSafeToExecuteUnconditionally(Instruction &Inst, | |||
| 164 | const DominatorTree *DT, | |||
| 165 | const TargetLibraryInfo *TLI, | |||
| 166 | const Loop *CurLoop, | |||
| 167 | const LoopSafetyInfo *SafetyInfo, | |||
| 168 | OptimizationRemarkEmitter *ORE, | |||
| 169 | const Instruction *CtxI = nullptr); | |||
| 170 | static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, | |||
| 171 | AliasSetTracker *CurAST, Loop *CurLoop, | |||
| 172 | AAResults *AA); | |||
| 173 | static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, | |||
| 174 | Loop *CurLoop, Instruction &I, | |||
| 175 | SinkAndHoistLICMFlags &Flags); | |||
| 176 | static bool pointerInvalidatedByBlockWithMSSA(BasicBlock &BB, MemorySSA &MSSA, | |||
| 177 | MemoryUse &MU); | |||
| 178 | static Instruction *cloneInstructionInExitBlock( | |||
| 179 | Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, | |||
| 180 | const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU); | |||
| 181 | ||||
| 182 | static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, | |||
| 183 | AliasSetTracker *AST, MemorySSAUpdater *MSSAU); | |||
| 184 | ||||
| 185 | static void moveInstructionBefore(Instruction &I, Instruction &Dest, | |||
| 186 | ICFLoopSafetyInfo &SafetyInfo, | |||
| 187 | MemorySSAUpdater *MSSAU, ScalarEvolution *SE); | |||
| 188 | ||||
| 189 | static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L, | |||
| 190 | function_ref<void(Instruction *)> Fn); | |||
| 191 | static SmallVector<SmallSetVector<Value *, 8>, 0> | |||
| 192 | collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L); | |||
| 193 | ||||
| 194 | namespace { | |||
| 195 | struct LoopInvariantCodeMotion { | |||
| 196 | bool runOnLoop(Loop *L, AAResults *AA, LoopInfo *LI, DominatorTree *DT, | |||
| 197 | BlockFrequencyInfo *BFI, TargetLibraryInfo *TLI, | |||
| 198 | TargetTransformInfo *TTI, ScalarEvolution *SE, MemorySSA *MSSA, | |||
| 199 | OptimizationRemarkEmitter *ORE, bool LoopNestMode = false); | |||
| 200 | ||||
| 201 | LoopInvariantCodeMotion(unsigned LicmMssaOptCap, | |||
| 202 | unsigned LicmMssaNoAccForPromotionCap) | |||
| 203 | : LicmMssaOptCap(LicmMssaOptCap), | |||
| 204 | LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap) {} | |||
| 205 | ||||
| 206 | private: | |||
| 207 | unsigned LicmMssaOptCap; | |||
| 208 | unsigned LicmMssaNoAccForPromotionCap; | |||
| 209 | ||||
| 210 | std::unique_ptr<AliasSetTracker> | |||
| 211 | collectAliasInfoForLoop(Loop *L, LoopInfo *LI, AAResults *AA); | |||
| 212 | }; | |||
| 213 | ||||
| 214 | struct LegacyLICMPass : public LoopPass { | |||
| 215 | static char ID; // Pass identification, replacement for typeid | |||
| 216 | LegacyLICMPass( | |||
| 217 | unsigned LicmMssaOptCap = SetLicmMssaOptCap, | |||
| 218 | unsigned LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap) | |||
| 219 | : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) { | |||
| 220 | initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry()); | |||
| 221 | } | |||
| 222 | ||||
| 223 | bool runOnLoop(Loop *L, LPPassManager &LPM) override { | |||
| 224 | if (skipLoop(L)) | |||
| 225 | return false; | |||
| 226 | ||||
| 227 | LLVM_DEBUG(dbgs() << "Perform LICM on Loop with header at block "do { } while (false) | |||
| 228 | << L->getHeader()->getNameOrAsOperand() << "\n")do { } while (false); | |||
| 229 | ||||
| 230 | auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); | |||
| 231 | MemorySSA *MSSA = EnableMSSALoopDependency | |||
| 232 | ? (&getAnalysis<MemorySSAWrapperPass>().getMSSA()) | |||
| 233 | : nullptr; | |||
| 234 | bool hasProfileData = L->getHeader()->getParent()->hasProfileData(); | |||
| 235 | BlockFrequencyInfo *BFI = | |||
| 236 | hasProfileData ? &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() | |||
| 237 | : nullptr; | |||
| 238 | // For the old PM, we can't use OptimizationRemarkEmitter as an analysis | |||
| 239 | // pass. Function analyses need to be preserved across loop transformations | |||
| 240 | // but ORE cannot be preserved (see comment before the pass definition). | |||
| 241 | OptimizationRemarkEmitter ORE(L->getHeader()->getParent()); | |||
| 242 | return LICM.runOnLoop( | |||
| 243 | L, &getAnalysis<AAResultsWrapperPass>().getAAResults(), | |||
| 244 | &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(), | |||
| 245 | &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), BFI, | |||
| 246 | &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI( | |||
| 247 | *L->getHeader()->getParent()), | |||
| 248 | &getAnalysis<TargetTransformInfoWrapperPass>().getTTI( | |||
| 249 | *L->getHeader()->getParent()), | |||
| 250 | SE ? &SE->getSE() : nullptr, MSSA, &ORE); | |||
| 251 | } | |||
| 252 | ||||
| 253 | /// This transformation requires natural loop information & requires that | |||
| 254 | /// loop preheaders be inserted into the CFG... | |||
| 255 | /// | |||
| 256 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||
| 257 | AU.addPreserved<DominatorTreeWrapperPass>(); | |||
| 258 | AU.addPreserved<LoopInfoWrapperPass>(); | |||
| 259 | AU.addRequired<TargetLibraryInfoWrapperPass>(); | |||
| 260 | if (EnableMSSALoopDependency) { | |||
| 261 | AU.addRequired<MemorySSAWrapperPass>(); | |||
| 262 | AU.addPreserved<MemorySSAWrapperPass>(); | |||
| 263 | } | |||
| 264 | AU.addRequired<TargetTransformInfoWrapperPass>(); | |||
| 265 | getLoopAnalysisUsage(AU); | |||
| 266 | LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU); | |||
| 267 | AU.addPreserved<LazyBlockFrequencyInfoPass>(); | |||
| 268 | AU.addPreserved<LazyBranchProbabilityInfoPass>(); | |||
| 269 | } | |||
| 270 | ||||
| 271 | private: | |||
| 272 | LoopInvariantCodeMotion LICM; | |||
| 273 | }; | |||
| 274 | } // namespace | |||
| 275 | ||||
| 276 | PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM, | |||
| 277 | LoopStandardAnalysisResults &AR, LPMUpdater &) { | |||
| 278 | // For the new PM, we also can't use OptimizationRemarkEmitter as an analysis | |||
| 279 | // pass. Function analyses need to be preserved across loop transformations | |||
| 280 | // but ORE cannot be preserved (see comment before the pass definition). | |||
| 281 | OptimizationRemarkEmitter ORE(L.getHeader()->getParent()); | |||
| 282 | ||||
| 283 | LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); | |||
| 284 | if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, AR.BFI, &AR.TLI, &AR.TTI, | |||
| 285 | &AR.SE, AR.MSSA, &ORE)) | |||
| 286 | return PreservedAnalyses::all(); | |||
| 287 | ||||
| 288 | auto PA = getLoopPassPreservedAnalyses(); | |||
| 289 | ||||
| 290 | PA.preserve<DominatorTreeAnalysis>(); | |||
| 291 | PA.preserve<LoopAnalysis>(); | |||
| 292 | if (AR.MSSA) | |||
| 293 | PA.preserve<MemorySSAAnalysis>(); | |||
| 294 | ||||
| 295 | return PA; | |||
| 296 | } | |||
| 297 | ||||
| 298 | PreservedAnalyses LNICMPass::run(LoopNest &LN, LoopAnalysisManager &AM, | |||
| 299 | LoopStandardAnalysisResults &AR, | |||
| 300 | LPMUpdater &) { | |||
| 301 | // For the new PM, we also can't use OptimizationRemarkEmitter as an analysis | |||
| 302 | // pass. Function analyses need to be preserved across loop transformations | |||
| 303 | // but ORE cannot be preserved (see comment before the pass definition). | |||
| 304 | OptimizationRemarkEmitter ORE(LN.getParent()); | |||
| 305 | ||||
| 306 | LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); | |||
| 307 | ||||
| 308 | Loop &OutermostLoop = LN.getOutermostLoop(); | |||
| 309 | bool Changed = LICM.runOnLoop(&OutermostLoop, &AR.AA, &AR.LI, &AR.DT, AR.BFI, | |||
| 310 | &AR.TLI, &AR.TTI, &AR.SE, AR.MSSA, &ORE, true); | |||
| 311 | ||||
| 312 | if (!Changed) | |||
| 313 | return PreservedAnalyses::all(); | |||
| 314 | ||||
| 315 | auto PA = getLoopPassPreservedAnalyses(); | |||
| 316 | ||||
| 317 | PA.preserve<DominatorTreeAnalysis>(); | |||
| 318 | PA.preserve<LoopAnalysis>(); | |||
| 319 | if (AR.MSSA) | |||
| 320 | PA.preserve<MemorySSAAnalysis>(); | |||
| 321 | ||||
| 322 | return PA; | |||
| 323 | } | |||
| 324 | ||||
| 325 | char LegacyLICMPass::ID = 0; | |||
| 326 | INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion",static void *initializeLegacyLICMPassPassOnce(PassRegistry & Registry) { | |||
| 327 | false, false)static void *initializeLegacyLICMPassPassOnce(PassRegistry & Registry) { | |||
| 328 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | |||
| 329 | INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry); | |||
| 330 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | |||
| 331 | INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry); | |||
| 332 | INITIALIZE_PASS_DEPENDENCY(LazyBFIPass)initializeLazyBFIPassPass(Registry); | |||
| 333 | INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false,PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm" , &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor <LegacyLICMPass>), false, false); Registry.registerPass (*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag ; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry ) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce , std::ref(Registry)); } | |||
| 334 | false)PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm" , &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor <LegacyLICMPass>), false, false); Registry.registerPass (*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag ; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry ) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce , std::ref(Registry)); } | |||
| 335 | ||||
| 336 | Pass *llvm::createLICMPass() { return new LegacyLICMPass(); } | |||
| 337 | Pass *llvm::createLICMPass(unsigned LicmMssaOptCap, | |||
| 338 | unsigned LicmMssaNoAccForPromotionCap) { | |||
| 339 | return new LegacyLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); | |||
| 340 | } | |||
| 341 | ||||
| 342 | llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags(bool IsSink, Loop *L, | |||
| 343 | MemorySSA *MSSA) | |||
| 344 | : SinkAndHoistLICMFlags(SetLicmMssaOptCap, SetLicmMssaNoAccForPromotionCap, | |||
| 345 | IsSink, L, MSSA) {} | |||
| 346 | ||||
| 347 | llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags( | |||
| 348 | unsigned LicmMssaOptCap, unsigned LicmMssaNoAccForPromotionCap, bool IsSink, | |||
| 349 | Loop *L, MemorySSA *MSSA) | |||
| 350 | : LicmMssaOptCap(LicmMssaOptCap), | |||
| 351 | LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap), | |||
| 352 | IsSink(IsSink) { | |||
| 353 | assert(((L != nullptr) == (MSSA != nullptr)) &&((void)0) | |||
| 354 | "Unexpected values for SinkAndHoistLICMFlags")((void)0); | |||
| 355 | if (!MSSA) | |||
| 356 | return; | |||
| 357 | ||||
| 358 | unsigned AccessCapCount = 0; | |||
| 359 | for (auto *BB : L->getBlocks()) | |||
| 360 | if (const auto *Accesses = MSSA->getBlockAccesses(BB)) | |||
| 361 | for (const auto &MA : *Accesses) { | |||
| 362 | (void)MA; | |||
| 363 | ++AccessCapCount; | |||
| 364 | if (AccessCapCount > LicmMssaNoAccForPromotionCap) { | |||
| 365 | NoOfMemAccTooLarge = true; | |||
| 366 | return; | |||
| 367 | } | |||
| 368 | } | |||
| 369 | } | |||
| 370 | ||||
| 371 | /// Hoist expressions out of the specified loop. Note, alias info for inner | |||
| 372 | /// loop is not preserved so it is not a good idea to run LICM multiple | |||
| 373 | /// times on one loop. | |||
| 374 | bool LoopInvariantCodeMotion::runOnLoop( | |||
| 375 | Loop *L, AAResults *AA, LoopInfo *LI, DominatorTree *DT, | |||
| 376 | BlockFrequencyInfo *BFI, TargetLibraryInfo *TLI, TargetTransformInfo *TTI, | |||
| 377 | ScalarEvolution *SE, MemorySSA *MSSA, OptimizationRemarkEmitter *ORE, | |||
| 378 | bool LoopNestMode) { | |||
| 379 | bool Changed = false; | |||
| 380 | ||||
| 381 | assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.")((void)0); | |||
| 382 | ||||
| 383 | // If this loop has metadata indicating that LICM is not to be performed then | |||
| 384 | // just exit. | |||
| 385 | if (hasDisableLICMTransformsHint(L)) { | |||
| 386 | return false; | |||
| 387 | } | |||
| 388 | ||||
| 389 | std::unique_ptr<AliasSetTracker> CurAST; | |||
| 390 | std::unique_ptr<MemorySSAUpdater> MSSAU; | |||
| 391 | std::unique_ptr<SinkAndHoistLICMFlags> Flags; | |||
| 392 | ||||
| 393 | // Don't sink stores from loops with coroutine suspend instructions. | |||
| 394 | // LICM would sink instructions into the default destination of | |||
| 395 | // the coroutine switch. The default destination of the switch is to | |||
| 396 | // handle the case where the coroutine is suspended, by which point the | |||
| 397 | // coroutine frame may have been destroyed. No instruction can be sunk there. | |||
| 398 | // FIXME: This would unfortunately hurt the performance of coroutines, however | |||
| 399 | // there is currently no general solution for this. Similar issues could also | |||
| 400 | // potentially happen in other passes where instructions are being moved | |||
| 401 | // across that edge. | |||
| 402 | bool HasCoroSuspendInst = llvm::any_of(L->getBlocks(), [](BasicBlock *BB) { | |||
| 403 | return llvm::any_of(*BB, [](Instruction &I) { | |||
| 404 | IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I); | |||
| 405 | return II && II->getIntrinsicID() == Intrinsic::coro_suspend; | |||
| 406 | }); | |||
| 407 | }); | |||
| 408 | ||||
| 409 | if (!MSSA) { | |||
| 410 | LLVM_DEBUG(dbgs() << "LICM: Using Alias Set Tracker.\n")do { } while (false); | |||
| 411 | CurAST = collectAliasInfoForLoop(L, LI, AA); | |||
| 412 | Flags = std::make_unique<SinkAndHoistLICMFlags>( | |||
| 413 | LicmMssaOptCap, LicmMssaNoAccForPromotionCap, /*IsSink=*/true); | |||
| 414 | } else { | |||
| 415 | LLVM_DEBUG(dbgs() << "LICM: Using MemorySSA.\n")do { } while (false); | |||
| 416 | MSSAU = std::make_unique<MemorySSAUpdater>(MSSA); | |||
| 417 | Flags = std::make_unique<SinkAndHoistLICMFlags>( | |||
| 418 | LicmMssaOptCap, LicmMssaNoAccForPromotionCap, /*IsSink=*/true, L, MSSA); | |||
| 419 | } | |||
| 420 | ||||
| 421 | // Get the preheader block to move instructions into... | |||
| 422 | BasicBlock *Preheader = L->getLoopPreheader(); | |||
| 423 | ||||
| 424 | // Compute loop safety information. | |||
| 425 | ICFLoopSafetyInfo SafetyInfo; | |||
| 426 | SafetyInfo.computeLoopSafetyInfo(L); | |||
| 427 | ||||
| 428 | // We want to visit all of the instructions in this loop... that are not parts | |||
| 429 | // of our subloops (they have already had their invariants hoisted out of | |||
| 430 | // their loop, into this loop, so there is no need to process the BODIES of | |||
| 431 | // the subloops). | |||
| 432 | // | |||
| 433 | // Traverse the body of the loop in depth first order on the dominator tree so | |||
| 434 | // that we are guaranteed to see definitions before we see uses. This allows | |||
| 435 | // us to sink instructions in one pass, without iteration. After sinking | |||
| 436 | // instructions, we perform another pass to hoist them out of the loop. | |||
| 437 | if (L->hasDedicatedExits()) | |||
| 438 | Changed |= | |||
| 439 | sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, BFI, TLI, TTI, L, | |||
| 440 | CurAST.get(), MSSAU.get(), &SafetyInfo, *Flags.get(), ORE); | |||
| 441 | Flags->setIsSink(false); | |||
| 442 | if (Preheader) | |||
| 443 | Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, BFI, TLI, L, | |||
| 444 | CurAST.get(), MSSAU.get(), SE, &SafetyInfo, | |||
| 445 | *Flags.get(), ORE, LoopNestMode); | |||
| 446 | ||||
| 447 | // Now that all loop invariants have been removed from the loop, promote any | |||
| 448 | // memory references to scalars that we can. | |||
| 449 | // Don't sink stores from loops without dedicated block exits. Exits | |||
| 450 | // containing indirect branches are not transformed by loop simplify, | |||
| 451 | // make sure we catch that. An additional load may be generated in the | |||
| 452 | // preheader for SSA updater, so also avoid sinking when no preheader | |||
| 453 | // is available. | |||
| 454 | if (!DisablePromotion && Preheader && L->hasDedicatedExits() && | |||
| 455 | !Flags->tooManyMemoryAccesses() && !HasCoroSuspendInst) { | |||
| 456 | // Figure out the loop exits and their insertion points | |||
| 457 | SmallVector<BasicBlock *, 8> ExitBlocks; | |||
| 458 | L->getUniqueExitBlocks(ExitBlocks); | |||
| 459 | ||||
| 460 | // We can't insert into a catchswitch. | |||
| 461 | bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) { | |||
| 462 | return isa<CatchSwitchInst>(Exit->getTerminator()); | |||
| 463 | }); | |||
| 464 | ||||
| 465 | if (!HasCatchSwitch) { | |||
| 466 | SmallVector<Instruction *, 8> InsertPts; | |||
| 467 | SmallVector<MemoryAccess *, 8> MSSAInsertPts; | |||
| 468 | InsertPts.reserve(ExitBlocks.size()); | |||
| 469 | if (MSSAU) | |||
| 470 | MSSAInsertPts.reserve(ExitBlocks.size()); | |||
| 471 | for (BasicBlock *ExitBlock : ExitBlocks) { | |||
| 472 | InsertPts.push_back(&*ExitBlock->getFirstInsertionPt()); | |||
| 473 | if (MSSAU) | |||
| 474 | MSSAInsertPts.push_back(nullptr); | |||
| 475 | } | |||
| 476 | ||||
| 477 | PredIteratorCache PIC; | |||
| 478 | ||||
| 479 | bool Promoted = false; | |||
| 480 | if (CurAST.get()) { | |||
| 481 | // Loop over all of the alias sets in the tracker object. | |||
| 482 | for (AliasSet &AS : *CurAST) { | |||
| 483 | // We can promote this alias set if it has a store, if it is a "Must" | |||
| 484 | // alias set, if the pointer is loop invariant, and if we are not | |||
| 485 | // eliminating any volatile loads or stores. | |||
| 486 | if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || | |||
| 487 | !L->isLoopInvariant(AS.begin()->getValue())) | |||
| 488 | continue; | |||
| 489 | ||||
| 490 | assert(((void)0) | |||
| 491 | !AS.empty() &&((void)0) | |||
| 492 | "Must alias set should have at least one pointer element in it!")((void)0); | |||
| 493 | ||||
| 494 | SmallSetVector<Value *, 8> PointerMustAliases; | |||
| 495 | for (const auto &ASI : AS) | |||
| 496 | PointerMustAliases.insert(ASI.getValue()); | |||
| 497 | ||||
| 498 | Promoted |= promoteLoopAccessesToScalars( | |||
| 499 | PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC, LI, | |||
| 500 | DT, TLI, L, CurAST.get(), MSSAU.get(), &SafetyInfo, ORE); | |||
| 501 | } | |||
| 502 | } else { | |||
| 503 | // Promoting one set of accesses may make the pointers for another set | |||
| 504 | // loop invariant, so run this in a loop (with the MaybePromotable set | |||
| 505 | // decreasing in size over time). | |||
| 506 | bool LocalPromoted; | |||
| 507 | do { | |||
| 508 | LocalPromoted = false; | |||
| 509 | for (const SmallSetVector<Value *, 8> &PointerMustAliases : | |||
| 510 | collectPromotionCandidates(MSSA, AA, L)) { | |||
| 511 | LocalPromoted |= promoteLoopAccessesToScalars( | |||
| 512 | PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC, | |||
| 513 | LI, DT, TLI, L, /*AST*/nullptr, MSSAU.get(), &SafetyInfo, ORE); | |||
| 514 | } | |||
| 515 | Promoted |= LocalPromoted; | |||
| 516 | } while (LocalPromoted); | |||
| 517 | } | |||
| 518 | ||||
| 519 | // Once we have promoted values across the loop body we have to | |||
| 520 | // recursively reform LCSSA as any nested loop may now have values defined | |||
| 521 | // within the loop used in the outer loop. | |||
| 522 | // FIXME: This is really heavy handed. It would be a bit better to use an | |||
| 523 | // SSAUpdater strategy during promotion that was LCSSA aware and reformed | |||
| 524 | // it as it went. | |||
| 525 | if (Promoted) | |||
| 526 | formLCSSARecursively(*L, *DT, LI, SE); | |||
| 527 | ||||
| 528 | Changed |= Promoted; | |||
| 529 | } | |||
| 530 | } | |||
| 531 | ||||
| 532 | // Check that neither this loop nor its parent have had LCSSA broken. LICM is | |||
| 533 | // specifically moving instructions across the loop boundary and so it is | |||
| 534 | // especially in need of sanity checking here. | |||
| 535 | assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!")((void)0); | |||
| 536 | assert((L->isOutermost() || L->getParentLoop()->isLCSSAForm(*DT)) &&((void)0) | |||
| 537 | "Parent loop not left in LCSSA form after LICM!")((void)0); | |||
| 538 | ||||
| 539 | if (MSSAU.get() && VerifyMemorySSA) | |||
| 540 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 541 | ||||
| 542 | if (Changed && SE) | |||
| 543 | SE->forgetLoopDispositions(L); | |||
| 544 | return Changed; | |||
| 545 | } | |||
| 546 | ||||
| 547 | /// Walk the specified region of the CFG (defined by all blocks dominated by | |||
| 548 | /// the specified block, and that are in the current loop) in reverse depth | |||
| 549 | /// first order w.r.t the DominatorTree. This allows us to visit uses before | |||
| 550 | /// definitions, allowing us to sink a loop body in one pass without iteration. | |||
| 551 | /// | |||
| 552 | bool llvm::sinkRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI, | |||
| 553 | DominatorTree *DT, BlockFrequencyInfo *BFI, | |||
| 554 | TargetLibraryInfo *TLI, TargetTransformInfo *TTI, | |||
| 555 | Loop *CurLoop, AliasSetTracker *CurAST, | |||
| 556 | MemorySSAUpdater *MSSAU, ICFLoopSafetyInfo *SafetyInfo, | |||
| 557 | SinkAndHoistLICMFlags &Flags, | |||
| 558 | OptimizationRemarkEmitter *ORE) { | |||
| 559 | ||||
| 560 | // Verify inputs. | |||
| 561 | assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((void)0) | |||
| 562 | CurLoop != nullptr && SafetyInfo != nullptr &&((void)0) | |||
| 563 | "Unexpected input to sinkRegion.")((void)0); | |||
| 564 | assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((void)0) | |||
| 565 | "Either AliasSetTracker or MemorySSA should be initialized.")((void)0); | |||
| 566 | ||||
| 567 | // We want to visit children before parents. We will enque all the parents | |||
| 568 | // before their children in the worklist and process the worklist in reverse | |||
| 569 | // order. | |||
| 570 | SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop); | |||
| 571 | ||||
| 572 | bool Changed = false; | |||
| 573 | for (DomTreeNode *DTN : reverse(Worklist)) { | |||
| 574 | BasicBlock *BB = DTN->getBlock(); | |||
| 575 | // Only need to process the contents of this block if it is not part of a | |||
| 576 | // subloop (which would already have been processed). | |||
| 577 | if (inSubLoop(BB, CurLoop, LI)) | |||
| 578 | continue; | |||
| 579 | ||||
| 580 | for (BasicBlock::iterator II = BB->end(); II != BB->begin();) { | |||
| 581 | Instruction &I = *--II; | |||
| 582 | ||||
| 583 | // The instruction is not used in the loop if it is dead. In this case, | |||
| 584 | // we just delete it instead of sinking it. | |||
| 585 | if (isInstructionTriviallyDead(&I, TLI)) { | |||
| 586 | LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n')do { } while (false); | |||
| 587 | salvageKnowledge(&I); | |||
| 588 | salvageDebugInfo(I); | |||
| 589 | ++II; | |||
| 590 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 591 | Changed = true; | |||
| 592 | continue; | |||
| 593 | } | |||
| 594 | ||||
| 595 | // Check to see if we can sink this instruction to the exit blocks | |||
| 596 | // of the loop. We can do this if the all users of the instruction are | |||
| 597 | // outside of the loop. In this case, it doesn't even matter if the | |||
| 598 | // operands of the instruction are loop invariant. | |||
| 599 | // | |||
| 600 | bool FreeInLoop = false; | |||
| 601 | if (!I.mayHaveSideEffects() && | |||
| 602 | isNotUsedOrFreeInLoop(I, CurLoop, SafetyInfo, TTI, FreeInLoop) && | |||
| 603 | canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, | |||
| 604 | ORE)) { | |||
| 605 | if (sink(I, LI, DT, BFI, CurLoop, SafetyInfo, MSSAU, ORE)) { | |||
| 606 | if (!FreeInLoop) { | |||
| 607 | ++II; | |||
| 608 | salvageDebugInfo(I); | |||
| 609 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 610 | } | |||
| 611 | Changed = true; | |||
| 612 | } | |||
| 613 | } | |||
| 614 | } | |||
| 615 | } | |||
| 616 | if (MSSAU && VerifyMemorySSA) | |||
| 617 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 618 | return Changed; | |||
| 619 | } | |||
| 620 | ||||
| 621 | namespace { | |||
| 622 | // This is a helper class for hoistRegion to make it able to hoist control flow | |||
| 623 | // in order to be able to hoist phis. The way this works is that we initially | |||
| 624 | // start hoisting to the loop preheader, and when we see a loop invariant branch | |||
| 625 | // we make note of this. When we then come to hoist an instruction that's | |||
| 626 | // conditional on such a branch we duplicate the branch and the relevant control | |||
| 627 | // flow, then hoist the instruction into the block corresponding to its original | |||
| 628 | // block in the duplicated control flow. | |||
| 629 | class ControlFlowHoister { | |||
| 630 | private: | |||
| 631 | // Information about the loop we are hoisting from | |||
| 632 | LoopInfo *LI; | |||
| 633 | DominatorTree *DT; | |||
| 634 | Loop *CurLoop; | |||
| 635 | MemorySSAUpdater *MSSAU; | |||
| 636 | ||||
| 637 | // A map of blocks in the loop to the block their instructions will be hoisted | |||
| 638 | // to. | |||
| 639 | DenseMap<BasicBlock *, BasicBlock *> HoistDestinationMap; | |||
| 640 | ||||
| 641 | // The branches that we can hoist, mapped to the block that marks a | |||
| 642 | // convergence point of their control flow. | |||
| 643 | DenseMap<BranchInst *, BasicBlock *> HoistableBranches; | |||
| 644 | ||||
| 645 | public: | |||
| 646 | ControlFlowHoister(LoopInfo *LI, DominatorTree *DT, Loop *CurLoop, | |||
| 647 | MemorySSAUpdater *MSSAU) | |||
| 648 | : LI(LI), DT(DT), CurLoop(CurLoop), MSSAU(MSSAU) {} | |||
| 649 | ||||
| 650 | void registerPossiblyHoistableBranch(BranchInst *BI) { | |||
| 651 | // We can only hoist conditional branches with loop invariant operands. | |||
| 652 | if (!ControlFlowHoisting || !BI->isConditional() || | |||
| 653 | !CurLoop->hasLoopInvariantOperands(BI)) | |||
| 654 | return; | |||
| 655 | ||||
| 656 | // The branch destinations need to be in the loop, and we don't gain | |||
| 657 | // anything by duplicating conditional branches with duplicate successors, | |||
| 658 | // as it's essentially the same as an unconditional branch. | |||
| 659 | BasicBlock *TrueDest = BI->getSuccessor(0); | |||
| 660 | BasicBlock *FalseDest = BI->getSuccessor(1); | |||
| 661 | if (!CurLoop->contains(TrueDest) || !CurLoop->contains(FalseDest) || | |||
| 662 | TrueDest == FalseDest) | |||
| 663 | return; | |||
| 664 | ||||
| 665 | // We can hoist BI if one branch destination is the successor of the other, | |||
| 666 | // or both have common successor which we check by seeing if the | |||
| 667 | // intersection of their successors is non-empty. | |||
| 668 | // TODO: This could be expanded to allowing branches where both ends | |||
| 669 | // eventually converge to a single block. | |||
| 670 | SmallPtrSet<BasicBlock *, 4> TrueDestSucc, FalseDestSucc; | |||
| 671 | TrueDestSucc.insert(succ_begin(TrueDest), succ_end(TrueDest)); | |||
| 672 | FalseDestSucc.insert(succ_begin(FalseDest), succ_end(FalseDest)); | |||
| 673 | BasicBlock *CommonSucc = nullptr; | |||
| 674 | if (TrueDestSucc.count(FalseDest)) { | |||
| 675 | CommonSucc = FalseDest; | |||
| 676 | } else if (FalseDestSucc.count(TrueDest)) { | |||
| 677 | CommonSucc = TrueDest; | |||
| 678 | } else { | |||
| 679 | set_intersect(TrueDestSucc, FalseDestSucc); | |||
| 680 | // If there's one common successor use that. | |||
| 681 | if (TrueDestSucc.size() == 1) | |||
| 682 | CommonSucc = *TrueDestSucc.begin(); | |||
| 683 | // If there's more than one pick whichever appears first in the block list | |||
| 684 | // (we can't use the value returned by TrueDestSucc.begin() as it's | |||
| 685 | // unpredicatable which element gets returned). | |||
| 686 | else if (!TrueDestSucc.empty()) { | |||
| 687 | Function *F = TrueDest->getParent(); | |||
| 688 | auto IsSucc = [&](BasicBlock &BB) { return TrueDestSucc.count(&BB); }; | |||
| 689 | auto It = llvm::find_if(*F, IsSucc); | |||
| 690 | assert(It != F->end() && "Could not find successor in function")((void)0); | |||
| 691 | CommonSucc = &*It; | |||
| 692 | } | |||
| 693 | } | |||
| 694 | // The common successor has to be dominated by the branch, as otherwise | |||
| 695 | // there will be some other path to the successor that will not be | |||
| 696 | // controlled by this branch so any phi we hoist would be controlled by the | |||
| 697 | // wrong condition. This also takes care of avoiding hoisting of loop back | |||
| 698 | // edges. | |||
| 699 | // TODO: In some cases this could be relaxed if the successor is dominated | |||
| 700 | // by another block that's been hoisted and we can guarantee that the | |||
| 701 | // control flow has been replicated exactly. | |||
| 702 | if (CommonSucc && DT->dominates(BI, CommonSucc)) | |||
| 703 | HoistableBranches[BI] = CommonSucc; | |||
| 704 | } | |||
| 705 | ||||
| 706 | bool canHoistPHI(PHINode *PN) { | |||
| 707 | // The phi must have loop invariant operands. | |||
| 708 | if (!ControlFlowHoisting || !CurLoop->hasLoopInvariantOperands(PN)) | |||
| 709 | return false; | |||
| 710 | // We can hoist phis if the block they are in is the target of hoistable | |||
| 711 | // branches which cover all of the predecessors of the block. | |||
| 712 | SmallPtrSet<BasicBlock *, 8> PredecessorBlocks; | |||
| 713 | BasicBlock *BB = PN->getParent(); | |||
| 714 | for (BasicBlock *PredBB : predecessors(BB)) | |||
| 715 | PredecessorBlocks.insert(PredBB); | |||
| 716 | // If we have less predecessor blocks than predecessors then the phi will | |||
| 717 | // have more than one incoming value for the same block which we can't | |||
| 718 | // handle. | |||
| 719 | // TODO: This could be handled be erasing some of the duplicate incoming | |||
| 720 | // values. | |||
| 721 | if (PredecessorBlocks.size() != pred_size(BB)) | |||
| 722 | return false; | |||
| 723 | for (auto &Pair : HoistableBranches) { | |||
| 724 | if (Pair.second == BB) { | |||
| 725 | // Which blocks are predecessors via this branch depends on if the | |||
| 726 | // branch is triangle-like or diamond-like. | |||
| 727 | if (Pair.first->getSuccessor(0) == BB) { | |||
| 728 | PredecessorBlocks.erase(Pair.first->getParent()); | |||
| 729 | PredecessorBlocks.erase(Pair.first->getSuccessor(1)); | |||
| 730 | } else if (Pair.first->getSuccessor(1) == BB) { | |||
| 731 | PredecessorBlocks.erase(Pair.first->getParent()); | |||
| 732 | PredecessorBlocks.erase(Pair.first->getSuccessor(0)); | |||
| 733 | } else { | |||
| 734 | PredecessorBlocks.erase(Pair.first->getSuccessor(0)); | |||
| 735 | PredecessorBlocks.erase(Pair.first->getSuccessor(1)); | |||
| 736 | } | |||
| 737 | } | |||
| 738 | } | |||
| 739 | // PredecessorBlocks will now be empty if for every predecessor of BB we | |||
| 740 | // found a hoistable branch source. | |||
| 741 | return PredecessorBlocks.empty(); | |||
| 742 | } | |||
| 743 | ||||
| 744 | BasicBlock *getOrCreateHoistedBlock(BasicBlock *BB) { | |||
| 745 | if (!ControlFlowHoisting) | |||
| 746 | return CurLoop->getLoopPreheader(); | |||
| 747 | // If BB has already been hoisted, return that | |||
| 748 | if (HoistDestinationMap.count(BB)) | |||
| 749 | return HoistDestinationMap[BB]; | |||
| 750 | ||||
| 751 | // Check if this block is conditional based on a pending branch | |||
| 752 | auto HasBBAsSuccessor = | |||
| 753 | [&](DenseMap<BranchInst *, BasicBlock *>::value_type &Pair) { | |||
| 754 | return BB != Pair.second && (Pair.first->getSuccessor(0) == BB || | |||
| 755 | Pair.first->getSuccessor(1) == BB); | |||
| 756 | }; | |||
| 757 | auto It = llvm::find_if(HoistableBranches, HasBBAsSuccessor); | |||
| 758 | ||||
| 759 | // If not involved in a pending branch, hoist to preheader | |||
| 760 | BasicBlock *InitialPreheader = CurLoop->getLoopPreheader(); | |||
| 761 | if (It == HoistableBranches.end()) { | |||
| 762 | LLVM_DEBUG(dbgs() << "LICM using "do { } while (false) | |||
| 763 | << InitialPreheader->getNameOrAsOperand()do { } while (false) | |||
| 764 | << " as hoist destination for "do { } while (false) | |||
| 765 | << BB->getNameOrAsOperand() << "\n")do { } while (false); | |||
| 766 | HoistDestinationMap[BB] = InitialPreheader; | |||
| 767 | return InitialPreheader; | |||
| 768 | } | |||
| 769 | BranchInst *BI = It->first; | |||
| 770 | assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) ==((void)0) | |||
| 771 | HoistableBranches.end() &&((void)0) | |||
| 772 | "BB is expected to be the target of at most one branch")((void)0); | |||
| 773 | ||||
| 774 | LLVMContext &C = BB->getContext(); | |||
| 775 | BasicBlock *TrueDest = BI->getSuccessor(0); | |||
| 776 | BasicBlock *FalseDest = BI->getSuccessor(1); | |||
| 777 | BasicBlock *CommonSucc = HoistableBranches[BI]; | |||
| 778 | BasicBlock *HoistTarget = getOrCreateHoistedBlock(BI->getParent()); | |||
| 779 | ||||
| 780 | // Create hoisted versions of blocks that currently don't have them | |||
| 781 | auto CreateHoistedBlock = [&](BasicBlock *Orig) { | |||
| 782 | if (HoistDestinationMap.count(Orig)) | |||
| 783 | return HoistDestinationMap[Orig]; | |||
| 784 | BasicBlock *New = | |||
| 785 | BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent()); | |||
| 786 | HoistDestinationMap[Orig] = New; | |||
| 787 | DT->addNewBlock(New, HoistTarget); | |||
| 788 | if (CurLoop->getParentLoop()) | |||
| 789 | CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI); | |||
| 790 | ++NumCreatedBlocks; | |||
| 791 | LLVM_DEBUG(dbgs() << "LICM created " << New->getName()do { } while (false) | |||
| 792 | << " as hoist destination for " << Orig->getName()do { } while (false) | |||
| 793 | << "\n")do { } while (false); | |||
| 794 | return New; | |||
| 795 | }; | |||
| 796 | BasicBlock *HoistTrueDest = CreateHoistedBlock(TrueDest); | |||
| 797 | BasicBlock *HoistFalseDest = CreateHoistedBlock(FalseDest); | |||
| 798 | BasicBlock *HoistCommonSucc = CreateHoistedBlock(CommonSucc); | |||
| 799 | ||||
| 800 | // Link up these blocks with branches. | |||
| 801 | if (!HoistCommonSucc->getTerminator()) { | |||
| 802 | // The new common successor we've generated will branch to whatever that | |||
| 803 | // hoist target branched to. | |||
| 804 | BasicBlock *TargetSucc = HoistTarget->getSingleSuccessor(); | |||
| 805 | assert(TargetSucc && "Expected hoist target to have a single successor")((void)0); | |||
| 806 | HoistCommonSucc->moveBefore(TargetSucc); | |||
| 807 | BranchInst::Create(TargetSucc, HoistCommonSucc); | |||
| 808 | } | |||
| 809 | if (!HoistTrueDest->getTerminator()) { | |||
| 810 | HoistTrueDest->moveBefore(HoistCommonSucc); | |||
| 811 | BranchInst::Create(HoistCommonSucc, HoistTrueDest); | |||
| 812 | } | |||
| 813 | if (!HoistFalseDest->getTerminator()) { | |||
| 814 | HoistFalseDest->moveBefore(HoistCommonSucc); | |||
| 815 | BranchInst::Create(HoistCommonSucc, HoistFalseDest); | |||
| 816 | } | |||
| 817 | ||||
| 818 | // If BI is being cloned to what was originally the preheader then | |||
| 819 | // HoistCommonSucc will now be the new preheader. | |||
| 820 | if (HoistTarget == InitialPreheader) { | |||
| 821 | // Phis in the loop header now need to use the new preheader. | |||
| 822 | InitialPreheader->replaceSuccessorsPhiUsesWith(HoistCommonSucc); | |||
| 823 | if (MSSAU) | |||
| 824 | MSSAU->wireOldPredecessorsToNewImmediatePredecessor( | |||
| 825 | HoistTarget->getSingleSuccessor(), HoistCommonSucc, {HoistTarget}); | |||
| 826 | // The new preheader dominates the loop header. | |||
| 827 | DomTreeNode *PreheaderNode = DT->getNode(HoistCommonSucc); | |||
| 828 | DomTreeNode *HeaderNode = DT->getNode(CurLoop->getHeader()); | |||
| 829 | DT->changeImmediateDominator(HeaderNode, PreheaderNode); | |||
| 830 | // The preheader hoist destination is now the new preheader, with the | |||
| 831 | // exception of the hoist destination of this branch. | |||
| 832 | for (auto &Pair : HoistDestinationMap) | |||
| 833 | if (Pair.second == InitialPreheader && Pair.first != BI->getParent()) | |||
| 834 | Pair.second = HoistCommonSucc; | |||
| 835 | } | |||
| 836 | ||||
| 837 | // Now finally clone BI. | |||
| 838 | ReplaceInstWithInst( | |||
| 839 | HoistTarget->getTerminator(), | |||
| 840 | BranchInst::Create(HoistTrueDest, HoistFalseDest, BI->getCondition())); | |||
| 841 | ++NumClonedBranches; | |||
| 842 | ||||
| 843 | assert(CurLoop->getLoopPreheader() &&((void)0) | |||
| 844 | "Hoisting blocks should not have destroyed preheader")((void)0); | |||
| 845 | return HoistDestinationMap[BB]; | |||
| 846 | } | |||
| 847 | }; | |||
| 848 | } // namespace | |||
| 849 | ||||
| 850 | // Hoisting/sinking instruction out of a loop isn't always beneficial. It's only | |||
| 851 | // only worthwhile if the destination block is actually colder than current | |||
| 852 | // block. | |||
| 853 | static bool worthSinkOrHoistInst(Instruction &I, BasicBlock *DstBlock, | |||
| 854 | OptimizationRemarkEmitter *ORE, | |||
| 855 | BlockFrequencyInfo *BFI) { | |||
| 856 | // Check block frequency only when runtime profile is available | |||
| 857 | // to avoid pathological cases. With static profile, lean towards | |||
| 858 | // hosting because it helps canonicalize the loop for vectorizer. | |||
| 859 | if (!DstBlock->getParent()->hasProfileData()) | |||
| 860 | return true; | |||
| 861 | ||||
| 862 | if (!HoistSinkColdnessThreshold || !BFI) | |||
| 863 | return true; | |||
| 864 | ||||
| 865 | BasicBlock *SrcBlock = I.getParent(); | |||
| 866 | if (BFI->getBlockFreq(DstBlock).getFrequency() / HoistSinkColdnessThreshold > | |||
| 867 | BFI->getBlockFreq(SrcBlock).getFrequency()) { | |||
| 868 | ORE->emit([&]() { | |||
| 869 | return OptimizationRemarkMissed(DEBUG_TYPE"licm", "SinkHoistInst", &I) | |||
| 870 | << "failed to sink or hoist instruction because containing block " | |||
| 871 | "has lower frequency than destination block"; | |||
| 872 | }); | |||
| 873 | return false; | |||
| 874 | } | |||
| 875 | ||||
| 876 | return true; | |||
| 877 | } | |||
| 878 | ||||
| 879 | /// Walk the specified region of the CFG (defined by all blocks dominated by | |||
| 880 | /// the specified block, and that are in the current loop) in depth first | |||
| 881 | /// order w.r.t the DominatorTree. This allows us to visit definitions before | |||
| 882 | /// uses, allowing us to hoist a loop body in one pass without iteration. | |||
| 883 | /// | |||
| 884 | bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI, | |||
| 885 | DominatorTree *DT, BlockFrequencyInfo *BFI, | |||
| 886 | TargetLibraryInfo *TLI, Loop *CurLoop, | |||
| 887 | AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, | |||
| 888 | ScalarEvolution *SE, ICFLoopSafetyInfo *SafetyInfo, | |||
| 889 | SinkAndHoistLICMFlags &Flags, | |||
| 890 | OptimizationRemarkEmitter *ORE, bool LoopNestMode) { | |||
| 891 | // Verify inputs. | |||
| 892 | assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((void)0) | |||
| 893 | CurLoop != nullptr && SafetyInfo != nullptr &&((void)0) | |||
| 894 | "Unexpected input to hoistRegion.")((void)0); | |||
| 895 | assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((void)0) | |||
| 896 | "Either AliasSetTracker or MemorySSA should be initialized.")((void)0); | |||
| 897 | ||||
| 898 | ControlFlowHoister CFH(LI, DT, CurLoop, MSSAU); | |||
| 899 | ||||
| 900 | // Keep track of instructions that have been hoisted, as they may need to be | |||
| 901 | // re-hoisted if they end up not dominating all of their uses. | |||
| 902 | SmallVector<Instruction *, 16> HoistedInstructions; | |||
| 903 | ||||
| 904 | // For PHI hoisting to work we need to hoist blocks before their successors. | |||
| 905 | // We can do this by iterating through the blocks in the loop in reverse | |||
| 906 | // post-order. | |||
| 907 | LoopBlocksRPO Worklist(CurLoop); | |||
| 908 | Worklist.perform(LI); | |||
| 909 | bool Changed = false; | |||
| 910 | for (BasicBlock *BB : Worklist) { | |||
| 911 | // Only need to process the contents of this block if it is not part of a | |||
| 912 | // subloop (which would already have been processed). | |||
| 913 | if (!LoopNestMode && inSubLoop(BB, CurLoop, LI)) | |||
| 914 | continue; | |||
| 915 | ||||
| 916 | for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) { | |||
| 917 | Instruction &I = *II++; | |||
| 918 | // Try constant folding this instruction. If all the operands are | |||
| 919 | // constants, it is technically hoistable, but it would be better to | |||
| 920 | // just fold it. | |||
| 921 | if (Constant *C = ConstantFoldInstruction( | |||
| 922 | &I, I.getModule()->getDataLayout(), TLI)) { | |||
| 923 | LLVM_DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *Cdo { } while (false) | |||
| 924 | << '\n')do { } while (false); | |||
| 925 | if (CurAST) | |||
| 926 | CurAST->copyValue(&I, C); | |||
| 927 | // FIXME MSSA: Such replacements may make accesses unoptimized (D51960). | |||
| 928 | I.replaceAllUsesWith(C); | |||
| 929 | if (isInstructionTriviallyDead(&I, TLI)) | |||
| 930 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 931 | Changed = true; | |||
| 932 | continue; | |||
| 933 | } | |||
| 934 | ||||
| 935 | // Try hoisting the instruction out to the preheader. We can only do | |||
| 936 | // this if all of the operands of the instruction are loop invariant and | |||
| 937 | // if it is safe to hoist the instruction. We also check block frequency | |||
| 938 | // to make sure instruction only gets hoisted into colder blocks. | |||
| 939 | // TODO: It may be safe to hoist if we are hoisting to a conditional block | |||
| 940 | // and we have accurately duplicated the control flow from the loop header | |||
| 941 | // to that block. | |||
| 942 | if (CurLoop->hasLoopInvariantOperands(&I) && | |||
| 943 | canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, | |||
| 944 | ORE) && | |||
| 945 | worthSinkOrHoistInst(I, CurLoop->getLoopPreheader(), ORE, BFI) && | |||
| 946 | isSafeToExecuteUnconditionally( | |||
| 947 | I, DT, TLI, CurLoop, SafetyInfo, ORE, | |||
| 948 | CurLoop->getLoopPreheader()->getTerminator())) { | |||
| 949 | hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 950 | MSSAU, SE, ORE); | |||
| 951 | HoistedInstructions.push_back(&I); | |||
| 952 | Changed = true; | |||
| 953 | continue; | |||
| 954 | } | |||
| 955 | ||||
| 956 | // Attempt to remove floating point division out of the loop by | |||
| 957 | // converting it to a reciprocal multiplication. | |||
| 958 | if (I.getOpcode() == Instruction::FDiv && I.hasAllowReciprocal() && | |||
| 959 | CurLoop->isLoopInvariant(I.getOperand(1))) { | |||
| 960 | auto Divisor = I.getOperand(1); | |||
| 961 | auto One = llvm::ConstantFP::get(Divisor->getType(), 1.0); | |||
| 962 | auto ReciprocalDivisor = BinaryOperator::CreateFDiv(One, Divisor); | |||
| 963 | ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags()); | |||
| 964 | SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent()); | |||
| 965 | ReciprocalDivisor->insertBefore(&I); | |||
| 966 | ||||
| 967 | auto Product = | |||
| 968 | BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor); | |||
| 969 | Product->setFastMathFlags(I.getFastMathFlags()); | |||
| 970 | SafetyInfo->insertInstructionTo(Product, I.getParent()); | |||
| 971 | Product->insertAfter(&I); | |||
| 972 | I.replaceAllUsesWith(Product); | |||
| 973 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 974 | ||||
| 975 | hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), | |||
| 976 | SafetyInfo, MSSAU, SE, ORE); | |||
| 977 | HoistedInstructions.push_back(ReciprocalDivisor); | |||
| 978 | Changed = true; | |||
| 979 | continue; | |||
| 980 | } | |||
| 981 | ||||
| 982 | auto IsInvariantStart = [&](Instruction &I) { | |||
| 983 | using namespace PatternMatch; | |||
| 984 | return I.use_empty() && | |||
| 985 | match(&I, m_Intrinsic<Intrinsic::invariant_start>()); | |||
| 986 | }; | |||
| 987 | auto MustExecuteWithoutWritesBefore = [&](Instruction &I) { | |||
| 988 | return SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) && | |||
| 989 | SafetyInfo->doesNotWriteMemoryBefore(I, CurLoop); | |||
| 990 | }; | |||
| 991 | if ((IsInvariantStart(I) || isGuard(&I)) && | |||
| 992 | CurLoop->hasLoopInvariantOperands(&I) && | |||
| 993 | MustExecuteWithoutWritesBefore(I)) { | |||
| 994 | hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 995 | MSSAU, SE, ORE); | |||
| 996 | HoistedInstructions.push_back(&I); | |||
| 997 | Changed = true; | |||
| 998 | continue; | |||
| 999 | } | |||
| 1000 | ||||
| 1001 | if (PHINode *PN = dyn_cast<PHINode>(&I)) { | |||
| 1002 | if (CFH.canHoistPHI(PN)) { | |||
| 1003 | // Redirect incoming blocks first to ensure that we create hoisted | |||
| 1004 | // versions of those blocks before we hoist the phi. | |||
| 1005 | for (unsigned int i = 0; i < PN->getNumIncomingValues(); ++i) | |||
| 1006 | PN->setIncomingBlock( | |||
| 1007 | i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i))); | |||
| 1008 | hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 1009 | MSSAU, SE, ORE); | |||
| 1010 | assert(DT->dominates(PN, BB) && "Conditional PHIs not expected")((void)0); | |||
| 1011 | Changed = true; | |||
| 1012 | continue; | |||
| 1013 | } | |||
| 1014 | } | |||
| 1015 | ||||
| 1016 | // Remember possibly hoistable branches so we can actually hoist them | |||
| 1017 | // later if needed. | |||
| 1018 | if (BranchInst *BI = dyn_cast<BranchInst>(&I)) | |||
| 1019 | CFH.registerPossiblyHoistableBranch(BI); | |||
| 1020 | } | |||
| 1021 | } | |||
| 1022 | ||||
| 1023 | // If we hoisted instructions to a conditional block they may not dominate | |||
| 1024 | // their uses that weren't hoisted (such as phis where some operands are not | |||
| 1025 | // loop invariant). If so make them unconditional by moving them to their | |||
| 1026 | // immediate dominator. We iterate through the instructions in reverse order | |||
| 1027 | // which ensures that when we rehoist an instruction we rehoist its operands, | |||
| 1028 | // and also keep track of where in the block we are rehoisting to to make sure | |||
| 1029 | // that we rehoist instructions before the instructions that use them. | |||
| 1030 | Instruction *HoistPoint = nullptr; | |||
| 1031 | if (ControlFlowHoisting) { | |||
| 1032 | for (Instruction *I : reverse(HoistedInstructions)) { | |||
| 1033 | if (!llvm::all_of(I->uses(), | |||
| 1034 | [&](Use &U) { return DT->dominates(I, U); })) { | |||
| 1035 | BasicBlock *Dominator = | |||
| 1036 | DT->getNode(I->getParent())->getIDom()->getBlock(); | |||
| 1037 | if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) { | |||
| 1038 | if (HoistPoint) | |||
| 1039 | assert(DT->dominates(Dominator, HoistPoint->getParent()) &&((void)0) | |||
| 1040 | "New hoist point expected to dominate old hoist point")((void)0); | |||
| 1041 | HoistPoint = Dominator->getTerminator(); | |||
| 1042 | } | |||
| 1043 | LLVM_DEBUG(dbgs() << "LICM rehoisting to "do { } while (false) | |||
| 1044 | << HoistPoint->getParent()->getNameOrAsOperand()do { } while (false) | |||
| 1045 | << ": " << *I << "\n")do { } while (false); | |||
| 1046 | moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU, SE); | |||
| 1047 | HoistPoint = I; | |||
| 1048 | Changed = true; | |||
| 1049 | } | |||
| 1050 | } | |||
| 1051 | } | |||
| 1052 | if (MSSAU && VerifyMemorySSA) | |||
| 1053 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 1054 | ||||
| 1055 | // Now that we've finished hoisting make sure that LI and DT are still | |||
| 1056 | // valid. | |||
| 1057 | #ifdef EXPENSIVE_CHECKS | |||
| 1058 | if (Changed) { | |||
| 1059 | assert(DT->verify(DominatorTree::VerificationLevel::Fast) &&((void)0) | |||
| 1060 | "Dominator tree verification failed")((void)0); | |||
| 1061 | LI->verify(*DT); | |||
| 1062 | } | |||
| 1063 | #endif | |||
| 1064 | ||||
| 1065 | return Changed; | |||
| 1066 | } | |||
| 1067 | ||||
| 1068 | // Return true if LI is invariant within scope of the loop. LI is invariant if | |||
| 1069 | // CurLoop is dominated by an invariant.start representing the same memory | |||
| 1070 | // location and size as the memory location LI loads from, and also the | |||
| 1071 | // invariant.start has no uses. | |||
| 1072 | static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT, | |||
| 1073 | Loop *CurLoop) { | |||
| 1074 | Value *Addr = LI->getOperand(0); | |||
| 1075 | const DataLayout &DL = LI->getModule()->getDataLayout(); | |||
| 1076 | const TypeSize LocSizeInBits = DL.getTypeSizeInBits(LI->getType()); | |||
| 1077 | ||||
| 1078 | // It is not currently possible for clang to generate an invariant.start | |||
| 1079 | // intrinsic with scalable vector types because we don't support thread local | |||
| 1080 | // sizeless types and we don't permit sizeless types in structs or classes. | |||
| 1081 | // Furthermore, even if support is added for this in future the intrinsic | |||
| 1082 | // itself is defined to have a size of -1 for variable sized objects. This | |||
| 1083 | // makes it impossible to verify if the intrinsic envelops our region of | |||
| 1084 | // interest. For example, both <vscale x 32 x i8> and <vscale x 16 x i8> | |||
| 1085 | // types would have a -1 parameter, but the former is clearly double the size | |||
| 1086 | // of the latter. | |||
| 1087 | if (LocSizeInBits.isScalable()) | |||
| 1088 | return false; | |||
| 1089 | ||||
| 1090 | // if the type is i8 addrspace(x)*, we know this is the type of | |||
| 1091 | // llvm.invariant.start operand | |||
| 1092 | auto *PtrInt8Ty = PointerType::get(Type::getInt8Ty(LI->getContext()), | |||
| 1093 | LI->getPointerAddressSpace()); | |||
| 1094 | unsigned BitcastsVisited = 0; | |||
| 1095 | // Look through bitcasts until we reach the i8* type (this is invariant.start | |||
| 1096 | // operand type). | |||
| 1097 | while (Addr->getType() != PtrInt8Ty) { | |||
| 1098 | auto *BC = dyn_cast<BitCastInst>(Addr); | |||
| 1099 | // Avoid traversing high number of bitcast uses. | |||
| 1100 | if (++BitcastsVisited > MaxNumUsesTraversed || !BC) | |||
| 1101 | return false; | |||
| 1102 | Addr = BC->getOperand(0); | |||
| 1103 | } | |||
| 1104 | ||||
| 1105 | unsigned UsesVisited = 0; | |||
| 1106 | // Traverse all uses of the load operand value, to see if invariant.start is | |||
| 1107 | // one of the uses, and whether it dominates the load instruction. | |||
| 1108 | for (auto *U : Addr->users()) { | |||
| 1109 | // Avoid traversing for Load operand with high number of users. | |||
| 1110 | if (++UsesVisited > MaxNumUsesTraversed) | |||
| 1111 | return false; | |||
| 1112 | IntrinsicInst *II = dyn_cast<IntrinsicInst>(U); | |||
| 1113 | // If there are escaping uses of invariant.start instruction, the load maybe | |||
| 1114 | // non-invariant. | |||
| 1115 | if (!II || II->getIntrinsicID() != Intrinsic::invariant_start || | |||
| 1116 | !II->use_empty()) | |||
| 1117 | continue; | |||
| 1118 | ConstantInt *InvariantSize = cast<ConstantInt>(II->getArgOperand(0)); | |||
| 1119 | // The intrinsic supports having a -1 argument for variable sized objects | |||
| 1120 | // so we should check for that here. | |||
| 1121 | if (InvariantSize->isNegative()) | |||
| 1122 | continue; | |||
| 1123 | uint64_t InvariantSizeInBits = InvariantSize->getSExtValue() * 8; | |||
| 1124 | // Confirm the invariant.start location size contains the load operand size | |||
| 1125 | // in bits. Also, the invariant.start should dominate the load, and we | |||
| 1126 | // should not hoist the load out of a loop that contains this dominating | |||
| 1127 | // invariant.start. | |||
| 1128 | if (LocSizeInBits.getFixedSize() <= InvariantSizeInBits && | |||
| 1129 | DT->properlyDominates(II->getParent(), CurLoop->getHeader())) | |||
| 1130 | return true; | |||
| 1131 | } | |||
| 1132 | ||||
| 1133 | return false; | |||
| 1134 | } | |||
| 1135 | ||||
| 1136 | namespace { | |||
| 1137 | /// Return true if-and-only-if we know how to (mechanically) both hoist and | |||
| 1138 | /// sink a given instruction out of a loop. Does not address legality | |||
| 1139 | /// concerns such as aliasing or speculation safety. | |||
| 1140 | bool isHoistableAndSinkableInst(Instruction &I) { | |||
| 1141 | // Only these instructions are hoistable/sinkable. | |||
| 1142 | return (isa<LoadInst>(I) || isa<StoreInst>(I) || isa<CallInst>(I) || | |||
| 1143 | isa<FenceInst>(I) || isa<CastInst>(I) || isa<UnaryOperator>(I) || | |||
| 1144 | isa<BinaryOperator>(I) || isa<SelectInst>(I) || | |||
| 1145 | isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || | |||
| 1146 | isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || | |||
| 1147 | isa<ShuffleVectorInst>(I) || isa<ExtractValueInst>(I) || | |||
| 1148 | isa<InsertValueInst>(I) || isa<FreezeInst>(I)); | |||
| 1149 | } | |||
| 1150 | /// Return true if all of the alias sets within this AST are known not to | |||
| 1151 | /// contain a Mod, or if MSSA knows there are no MemoryDefs in the loop. | |||
| 1152 | bool isReadOnly(AliasSetTracker *CurAST, const MemorySSAUpdater *MSSAU, | |||
| 1153 | const Loop *L) { | |||
| 1154 | if (CurAST) { | |||
| 1155 | for (AliasSet &AS : *CurAST) { | |||
| 1156 | if (!AS.isForwardingAliasSet() && AS.isMod()) { | |||
| 1157 | return false; | |||
| 1158 | } | |||
| 1159 | } | |||
| 1160 | return true; | |||
| 1161 | } else { /*MSSAU*/ | |||
| 1162 | for (auto *BB : L->getBlocks()) | |||
| 1163 | if (MSSAU->getMemorySSA()->getBlockDefs(BB)) | |||
| 1164 | return false; | |||
| 1165 | return true; | |||
| 1166 | } | |||
| 1167 | } | |||
| 1168 | ||||
| 1169 | /// Return true if I is the only Instruction with a MemoryAccess in L. | |||
| 1170 | bool isOnlyMemoryAccess(const Instruction *I, const Loop *L, | |||
| 1171 | const MemorySSAUpdater *MSSAU) { | |||
| 1172 | for (auto *BB : L->getBlocks()) | |||
| 1173 | if (auto *Accs = MSSAU->getMemorySSA()->getBlockAccesses(BB)) { | |||
| ||||
| 1174 | int NotAPhi = 0; | |||
| 1175 | for (const auto &Acc : *Accs) { | |||
| 1176 | if (isa<MemoryPhi>(&Acc)) | |||
| 1177 | continue; | |||
| 1178 | const auto *MUD = cast<MemoryUseOrDef>(&Acc); | |||
| 1179 | if (MUD->getMemoryInst() != I || NotAPhi++ == 1) | |||
| 1180 | return false; | |||
| 1181 | } | |||
| 1182 | } | |||
| 1183 | return true; | |||
| 1184 | } | |||
| 1185 | } | |||
| 1186 | ||||
| 1187 | bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, | |||
| 1188 | Loop *CurLoop, AliasSetTracker *CurAST, | |||
| 1189 | MemorySSAUpdater *MSSAU, | |||
| 1190 | bool TargetExecutesOncePerLoop, | |||
| 1191 | SinkAndHoistLICMFlags *Flags, | |||
| 1192 | OptimizationRemarkEmitter *ORE) { | |||
| 1193 | assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((void)0) | |||
| 1194 | "Either AliasSetTracker or MemorySSA should be initialized.")((void)0); | |||
| 1195 | ||||
| 1196 | // If we don't understand the instruction, bail early. | |||
| 1197 | if (!isHoistableAndSinkableInst(I)) | |||
| ||||
| 1198 | return false; | |||
| 1199 | ||||
| 1200 | MemorySSA *MSSA = MSSAU ? MSSAU->getMemorySSA() : nullptr; | |||
| 1201 | if (MSSA
| |||
| 1202 | assert(Flags != nullptr && "Flags cannot be null.")((void)0); | |||
| 1203 | ||||
| 1204 | // Loads have extra constraints we have to verify before we can hoist them. | |||
| 1205 | if (LoadInst *LI
| |||
| 1206 | if (!LI->isUnordered()) | |||
| 1207 | return false; // Don't sink/hoist volatile or ordered atomic loads! | |||
| 1208 | ||||
| 1209 | // Loads from constant memory are always safe to move, even if they end up | |||
| 1210 | // in the same alias set as something that ends up being modified. | |||
| 1211 | if (AA->pointsToConstantMemory(LI->getOperand(0))) | |||
| 1212 | return true; | |||
| 1213 | if (LI->hasMetadata(LLVMContext::MD_invariant_load)) | |||
| 1214 | return true; | |||
| 1215 | ||||
| 1216 | if (LI->isAtomic() && !TargetExecutesOncePerLoop) | |||
| 1217 | return false; // Don't risk duplicating unordered loads | |||
| 1218 | ||||
| 1219 | // This checks for an invariant.start dominating the load. | |||
| 1220 | if (isLoadInvariantInLoop(LI, DT, CurLoop)) | |||
| 1221 | return true; | |||
| 1222 | ||||
| 1223 | bool Invalidated; | |||
| 1224 | if (CurAST) | |||
| 1225 | Invalidated = pointerInvalidatedByLoop(MemoryLocation::get(LI), CurAST, | |||
| 1226 | CurLoop, AA); | |||
| 1227 | else | |||
| 1228 | Invalidated = pointerInvalidatedByLoopWithMSSA( | |||
| 1229 | MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(LI)), CurLoop, I, *Flags); | |||
| 1230 | // Check loop-invariant address because this may also be a sinkable load | |||
| 1231 | // whose address is not necessarily loop-invariant. | |||
| 1232 | if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand())) | |||
| 1233 | ORE->emit([&]() { | |||
| 1234 | return OptimizationRemarkMissed( | |||
| 1235 | DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressInvalidated", LI) | |||
| 1236 | << "failed to move load with loop-invariant address " | |||
| 1237 | "because the loop may invalidate its value"; | |||
| 1238 | }); | |||
| 1239 | ||||
| 1240 | return !Invalidated; | |||
| 1241 | } else if (CallInst *CI
| |||
| 1242 | // Don't sink or hoist dbg info; it's legal, but not useful. | |||
| 1243 | if (isa<DbgInfoIntrinsic>(I)) | |||
| 1244 | return false; | |||
| 1245 | ||||
| 1246 | // Don't sink calls which can throw. | |||
| 1247 | if (CI->mayThrow()) | |||
| 1248 | return false; | |||
| 1249 | ||||
| 1250 | // Convergent attribute has been used on operations that involve | |||
| 1251 | // inter-thread communication which results are implicitly affected by the | |||
| 1252 | // enclosing control flows. It is not safe to hoist or sink such operations | |||
| 1253 | // across control flow. | |||
| 1254 | if (CI->isConvergent()) | |||
| 1255 | return false; | |||
| 1256 | ||||
| 1257 | using namespace PatternMatch; | |||
| 1258 | if (match(CI, m_Intrinsic<Intrinsic::assume>())) | |||
| 1259 | // Assumes don't actually alias anything or throw | |||
| 1260 | return true; | |||
| 1261 | ||||
| 1262 | if (match(CI, m_Intrinsic<Intrinsic::experimental_widenable_condition>())) | |||
| 1263 | // Widenable conditions don't actually alias anything or throw | |||
| 1264 | return true; | |||
| 1265 | ||||
| 1266 | // Handle simple cases by querying alias analysis. | |||
| 1267 | FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI); | |||
| 1268 | if (Behavior == FMRB_DoesNotAccessMemory) | |||
| 1269 | return true; | |||
| 1270 | if (AAResults::onlyReadsMemory(Behavior)) { | |||
| 1271 | // A readonly argmemonly function only reads from memory pointed to by | |||
| 1272 | // it's arguments with arbitrary offsets. If we can prove there are no | |||
| 1273 | // writes to this memory in the loop, we can hoist or sink. | |||
| 1274 | if (AAResults::onlyAccessesArgPointees(Behavior)) { | |||
| 1275 | // TODO: expand to writeable arguments | |||
| 1276 | for (Value *Op : CI->arg_operands()) | |||
| 1277 | if (Op->getType()->isPointerTy()) { | |||
| 1278 | bool Invalidated; | |||
| 1279 | if (CurAST) | |||
| 1280 | Invalidated = pointerInvalidatedByLoop( | |||
| 1281 | MemoryLocation::getBeforeOrAfter(Op), CurAST, CurLoop, AA); | |||
| 1282 | else | |||
| 1283 | Invalidated = pointerInvalidatedByLoopWithMSSA( | |||
| 1284 | MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(CI)), CurLoop, I, | |||
| 1285 | *Flags); | |||
| 1286 | if (Invalidated) | |||
| 1287 | return false; | |||
| 1288 | } | |||
| 1289 | return true; | |||
| 1290 | } | |||
| 1291 | ||||
| 1292 | // If this call only reads from memory and there are no writes to memory | |||
| 1293 | // in the loop, we can hoist or sink the call as appropriate. | |||
| 1294 | if (isReadOnly(CurAST, MSSAU, CurLoop)) | |||
| 1295 | return true; | |||
| 1296 | } | |||
| 1297 | ||||
| 1298 | // FIXME: This should use mod/ref information to see if we can hoist or | |||
| 1299 | // sink the call. | |||
| 1300 | ||||
| 1301 | return false; | |||
| 1302 | } else if (auto *FI
| |||
| 1303 | // Fences alias (most) everything to provide ordering. For the moment, | |||
| 1304 | // just give up if there are any other memory operations in the loop. | |||
| 1305 | if (CurAST) { | |||
| 1306 | auto Begin = CurAST->begin(); | |||
| 1307 | assert(Begin != CurAST->end() && "must contain FI")((void)0); | |||
| 1308 | if (std::next(Begin) != CurAST->end()) | |||
| 1309 | // constant memory for instance, TODO: handle better | |||
| 1310 | return false; | |||
| 1311 | auto *UniqueI = Begin->getUniqueInstruction(); | |||
| 1312 | if (!UniqueI) | |||
| 1313 | // other memory op, give up | |||
| 1314 | return false; | |||
| 1315 | (void)FI; // suppress unused variable warning | |||
| 1316 | assert(UniqueI == FI && "AS must contain FI")((void)0); | |||
| 1317 | return true; | |||
| 1318 | } else // MSSAU | |||
| 1319 | return isOnlyMemoryAccess(FI, CurLoop, MSSAU); | |||
| 1320 | } else if (auto *SI = dyn_cast<StoreInst>(&I)) { | |||
| 1321 | if (!SI->isUnordered()) | |||
| 1322 | return false; // Don't sink/hoist volatile or ordered atomic store! | |||
| 1323 | ||||
| 1324 | // We can only hoist a store that we can prove writes a value which is not | |||
| 1325 | // read or overwritten within the loop. For those cases, we fallback to | |||
| 1326 | // load store promotion instead. TODO: We can extend this to cases where | |||
| 1327 | // there is exactly one write to the location and that write dominates an | |||
| 1328 | // arbitrary number of reads in the loop. | |||
| 1329 | if (CurAST) { | |||
| 1330 | auto &AS = CurAST->getAliasSetFor(MemoryLocation::get(SI)); | |||
| 1331 | ||||
| 1332 | if (AS.isRef() || !AS.isMustAlias()) | |||
| 1333 | // Quick exit test, handled by the full path below as well. | |||
| 1334 | return false; | |||
| 1335 | auto *UniqueI = AS.getUniqueInstruction(); | |||
| 1336 | if (!UniqueI) | |||
| 1337 | // other memory op, give up | |||
| 1338 | return false; | |||
| 1339 | assert(UniqueI == SI && "AS must contain SI")((void)0); | |||
| 1340 | return true; | |||
| 1341 | } else { // MSSAU | |||
| 1342 | if (isOnlyMemoryAccess(SI, CurLoop, MSSAU)) | |||
| 1343 | return true; | |||
| 1344 | // If there are more accesses than the Promotion cap or no "quota" to | |||
| 1345 | // check clobber, then give up as we're not walking a list that long. | |||
| 1346 | if (Flags->tooManyMemoryAccesses() || Flags->tooManyClobberingCalls()) | |||
| 1347 | return false; | |||
| 1348 | // If there are interfering Uses (i.e. their defining access is in the | |||
| 1349 | // loop), or ordered loads (stored as Defs!), don't move this store. | |||
| 1350 | // Could do better here, but this is conservatively correct. | |||
| 1351 | // TODO: Cache set of Uses on the first walk in runOnLoop, update when | |||
| 1352 | // moving accesses. Can also extend to dominating uses. | |||
| 1353 | auto *SIMD = MSSA->getMemoryAccess(SI); | |||
| 1354 | for (auto *BB : CurLoop->getBlocks()) | |||
| 1355 | if (auto *Accesses = MSSA->getBlockAccesses(BB)) { | |||
| 1356 | for (const auto &MA : *Accesses) | |||
| 1357 | if (const auto *MU = dyn_cast<MemoryUse>(&MA)) { | |||
| 1358 | auto *MD = MU->getDefiningAccess(); | |||
| 1359 | if (!MSSA->isLiveOnEntryDef(MD) && | |||
| 1360 | CurLoop->contains(MD->getBlock())) | |||
| 1361 | return false; | |||
| 1362 | // Disable hoisting past potentially interfering loads. Optimized | |||
| 1363 | // Uses may point to an access outside the loop, as getClobbering | |||
| 1364 | // checks the previous iteration when walking the backedge. | |||
| 1365 | // FIXME: More precise: no Uses that alias SI. | |||
| 1366 | if (!Flags->getIsSink() && !MSSA->dominates(SIMD, MU)) | |||
| 1367 | return false; | |||
| 1368 | } else if (const auto *MD = dyn_cast<MemoryDef>(&MA)) { | |||
| 1369 | if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) { | |||
| 1370 | (void)LI; // Silence warning. | |||
| 1371 | assert(!LI->isUnordered() && "Expected unordered load")((void)0); | |||
| 1372 | return false; | |||
| 1373 | } | |||
| 1374 | // Any call, while it may not be clobbering SI, it may be a use. | |||
| 1375 | if (auto *CI = dyn_cast<CallInst>(MD->getMemoryInst())) { | |||
| 1376 | // Check if the call may read from the memory location written | |||
| 1377 | // to by SI. Check CI's attributes and arguments; the number of | |||
| 1378 | // such checks performed is limited above by NoOfMemAccTooLarge. | |||
| 1379 | ModRefInfo MRI = AA->getModRefInfo(CI, MemoryLocation::get(SI)); | |||
| 1380 | if (isModOrRefSet(MRI)) | |||
| 1381 | return false; | |||
| 1382 | } | |||
| 1383 | } | |||
| 1384 | } | |||
| 1385 | auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI); | |||
| 1386 | Flags->incrementClobberingCalls(); | |||
| 1387 | // If there are no clobbering Defs in the loop, store is safe to hoist. | |||
| 1388 | return MSSA->isLiveOnEntryDef(Source) || | |||
| 1389 | !CurLoop->contains(Source->getBlock()); | |||
| 1390 | } | |||
| 1391 | } | |||
| 1392 | ||||
| 1393 | assert(!I.mayReadOrWriteMemory() && "unhandled aliasing")((void)0); | |||
| 1394 | ||||
| 1395 | // We've established mechanical ability and aliasing, it's up to the caller | |||
| 1396 | // to check fault safety | |||
| 1397 | return true; | |||
| 1398 | } | |||
| 1399 | ||||
| 1400 | /// Returns true if a PHINode is a trivially replaceable with an | |||
| 1401 | /// Instruction. | |||
| 1402 | /// This is true when all incoming values are that instruction. | |||
| 1403 | /// This pattern occurs most often with LCSSA PHI nodes. | |||
| 1404 | /// | |||
| 1405 | static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) { | |||
| 1406 | for (const Value *IncValue : PN.incoming_values()) | |||
| 1407 | if (IncValue != &I) | |||
| 1408 | return false; | |||
| 1409 | ||||
| 1410 | return true; | |||
| 1411 | } | |||
| 1412 | ||||
| 1413 | /// Return true if the instruction is free in the loop. | |||
| 1414 | static bool isFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 1415 | const TargetTransformInfo *TTI) { | |||
| 1416 | ||||
| 1417 | if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I)) { | |||
| 1418 | if (TTI->getUserCost(GEP, TargetTransformInfo::TCK_SizeAndLatency) != | |||
| 1419 | TargetTransformInfo::TCC_Free) | |||
| 1420 | return false; | |||
| 1421 | // For a GEP, we cannot simply use getUserCost because currently it | |||
| 1422 | // optimistically assume that a GEP will fold into addressing mode | |||
| 1423 | // regardless of its users. | |||
| 1424 | const BasicBlock *BB = GEP->getParent(); | |||
| 1425 | for (const User *U : GEP->users()) { | |||
| 1426 | const Instruction *UI = cast<Instruction>(U); | |||
| 1427 | if (CurLoop->contains(UI) && | |||
| 1428 | (BB != UI->getParent() || | |||
| 1429 | (!isa<StoreInst>(UI) && !isa<LoadInst>(UI)))) | |||
| 1430 | return false; | |||
| 1431 | } | |||
| 1432 | return true; | |||
| 1433 | } else | |||
| 1434 | return TTI->getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) == | |||
| 1435 | TargetTransformInfo::TCC_Free; | |||
| 1436 | } | |||
| 1437 | ||||
| 1438 | /// Return true if the only users of this instruction are outside of | |||
| 1439 | /// the loop. If this is true, we can sink the instruction to the exit | |||
| 1440 | /// blocks of the loop. | |||
| 1441 | /// | |||
| 1442 | /// We also return true if the instruction could be folded away in lowering. | |||
| 1443 | /// (e.g., a GEP can be folded into a load as an addressing mode in the loop). | |||
| 1444 | static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 1445 | const LoopSafetyInfo *SafetyInfo, | |||
| 1446 | TargetTransformInfo *TTI, bool &FreeInLoop) { | |||
| 1447 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1448 | bool IsFree = isFreeInLoop(I, CurLoop, TTI); | |||
| 1449 | for (const User *U : I.users()) { | |||
| 1450 | const Instruction *UI = cast<Instruction>(U); | |||
| 1451 | if (const PHINode *PN = dyn_cast<PHINode>(UI)) { | |||
| 1452 | const BasicBlock *BB = PN->getParent(); | |||
| 1453 | // We cannot sink uses in catchswitches. | |||
| 1454 | if (isa<CatchSwitchInst>(BB->getTerminator())) | |||
| 1455 | return false; | |||
| 1456 | ||||
| 1457 | // We need to sink a callsite to a unique funclet. Avoid sinking if the | |||
| 1458 | // phi use is too muddled. | |||
| 1459 | if (isa<CallInst>(I)) | |||
| 1460 | if (!BlockColors.empty() && | |||
| 1461 | BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1) | |||
| 1462 | return false; | |||
| 1463 | } | |||
| 1464 | ||||
| 1465 | if (CurLoop->contains(UI)) { | |||
| 1466 | if (IsFree) { | |||
| 1467 | FreeInLoop = true; | |||
| 1468 | continue; | |||
| 1469 | } | |||
| 1470 | return false; | |||
| 1471 | } | |||
| 1472 | } | |||
| 1473 | return true; | |||
| 1474 | } | |||
| 1475 | ||||
| 1476 | static Instruction *cloneInstructionInExitBlock( | |||
| 1477 | Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, | |||
| 1478 | const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) { | |||
| 1479 | Instruction *New; | |||
| 1480 | if (auto *CI = dyn_cast<CallInst>(&I)) { | |||
| 1481 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1482 | ||||
| 1483 | // Sinking call-sites need to be handled differently from other | |||
| 1484 | // instructions. The cloned call-site needs a funclet bundle operand | |||
| 1485 | // appropriate for its location in the CFG. | |||
| 1486 | SmallVector<OperandBundleDef, 1> OpBundles; | |||
| 1487 | for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles(); | |||
| 1488 | BundleIdx != BundleEnd; ++BundleIdx) { | |||
| 1489 | OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx); | |||
| 1490 | if (Bundle.getTagID() == LLVMContext::OB_funclet) | |||
| 1491 | continue; | |||
| 1492 | ||||
| 1493 | OpBundles.emplace_back(Bundle); | |||
| 1494 | } | |||
| 1495 | ||||
| 1496 | if (!BlockColors.empty()) { | |||
| 1497 | const ColorVector &CV = BlockColors.find(&ExitBlock)->second; | |||
| 1498 | assert(CV.size() == 1 && "non-unique color for exit block!")((void)0); | |||
| 1499 | BasicBlock *BBColor = CV.front(); | |||
| 1500 | Instruction *EHPad = BBColor->getFirstNonPHI(); | |||
| 1501 | if (EHPad->isEHPad()) | |||
| 1502 | OpBundles.emplace_back("funclet", EHPad); | |||
| 1503 | } | |||
| 1504 | ||||
| 1505 | New = CallInst::Create(CI, OpBundles); | |||
| 1506 | } else { | |||
| 1507 | New = I.clone(); | |||
| 1508 | } | |||
| 1509 | ||||
| 1510 | ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New); | |||
| 1511 | if (!I.getName().empty()) | |||
| 1512 | New->setName(I.getName() + ".le"); | |||
| 1513 | ||||
| 1514 | if (MSSAU && MSSAU->getMemorySSA()->getMemoryAccess(&I)) { | |||
| 1515 | // Create a new MemoryAccess and let MemorySSA set its defining access. | |||
| 1516 | MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB( | |||
| 1517 | New, nullptr, New->getParent(), MemorySSA::Beginning); | |||
| 1518 | if (NewMemAcc) { | |||
| 1519 | if (auto *MemDef = dyn_cast<MemoryDef>(NewMemAcc)) | |||
| 1520 | MSSAU->insertDef(MemDef, /*RenameUses=*/true); | |||
| 1521 | else { | |||
| 1522 | auto *MemUse = cast<MemoryUse>(NewMemAcc); | |||
| 1523 | MSSAU->insertUse(MemUse, /*RenameUses=*/true); | |||
| 1524 | } | |||
| 1525 | } | |||
| 1526 | } | |||
| 1527 | ||||
| 1528 | // Build LCSSA PHI nodes for any in-loop operands (if legal). Note that | |||
| 1529 | // this is particularly cheap because we can rip off the PHI node that we're | |||
| 1530 | // replacing for the number and blocks of the predecessors. | |||
| 1531 | // OPT: If this shows up in a profile, we can instead finish sinking all | |||
| 1532 | // invariant instructions, and then walk their operands to re-establish | |||
| 1533 | // LCSSA. That will eliminate creating PHI nodes just to nuke them when | |||
| 1534 | // sinking bottom-up. | |||
| 1535 | for (Use &Op : New->operands()) | |||
| 1536 | if (LI->wouldBeOutOfLoopUseRequiringLCSSA(Op.get(), PN.getParent())) { | |||
| 1537 | auto *OInst = cast<Instruction>(Op.get()); | |||
| 1538 | PHINode *OpPN = | |||
| 1539 | PHINode::Create(OInst->getType(), PN.getNumIncomingValues(), | |||
| 1540 | OInst->getName() + ".lcssa", &ExitBlock.front()); | |||
| 1541 | for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) | |||
| 1542 | OpPN->addIncoming(OInst, PN.getIncomingBlock(i)); | |||
| 1543 | Op = OpPN; | |||
| 1544 | } | |||
| 1545 | return New; | |||
| 1546 | } | |||
| 1547 | ||||
| 1548 | static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, | |||
| 1549 | AliasSetTracker *AST, MemorySSAUpdater *MSSAU) { | |||
| 1550 | if (AST) | |||
| 1551 | AST->deleteValue(&I); | |||
| 1552 | if (MSSAU) | |||
| 1553 | MSSAU->removeMemoryAccess(&I); | |||
| 1554 | SafetyInfo.removeInstruction(&I); | |||
| 1555 | I.eraseFromParent(); | |||
| 1556 | } | |||
| 1557 | ||||
| 1558 | static void moveInstructionBefore(Instruction &I, Instruction &Dest, | |||
| 1559 | ICFLoopSafetyInfo &SafetyInfo, | |||
| 1560 | MemorySSAUpdater *MSSAU, | |||
| 1561 | ScalarEvolution *SE) { | |||
| 1562 | SafetyInfo.removeInstruction(&I); | |||
| 1563 | SafetyInfo.insertInstructionTo(&I, Dest.getParent()); | |||
| 1564 | I.moveBefore(&Dest); | |||
| 1565 | if (MSSAU) | |||
| 1566 | if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>( | |||
| 1567 | MSSAU->getMemorySSA()->getMemoryAccess(&I))) | |||
| 1568 | MSSAU->moveToPlace(OldMemAcc, Dest.getParent(), | |||
| 1569 | MemorySSA::BeforeTerminator); | |||
| 1570 | if (SE) | |||
| 1571 | SE->forgetValue(&I); | |||
| 1572 | } | |||
| 1573 | ||||
| 1574 | static Instruction *sinkThroughTriviallyReplaceablePHI( | |||
| 1575 | PHINode *TPN, Instruction *I, LoopInfo *LI, | |||
| 1576 | SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies, | |||
| 1577 | const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop, | |||
| 1578 | MemorySSAUpdater *MSSAU) { | |||
| 1579 | assert(isTriviallyReplaceablePHI(*TPN, *I) &&((void)0) | |||
| 1580 | "Expect only trivially replaceable PHI")((void)0); | |||
| 1581 | BasicBlock *ExitBlock = TPN->getParent(); | |||
| 1582 | Instruction *New; | |||
| 1583 | auto It = SunkCopies.find(ExitBlock); | |||
| 1584 | if (It != SunkCopies.end()) | |||
| 1585 | New = It->second; | |||
| 1586 | else | |||
| 1587 | New = SunkCopies[ExitBlock] = cloneInstructionInExitBlock( | |||
| 1588 | *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU); | |||
| 1589 | return New; | |||
| 1590 | } | |||
| 1591 | ||||
| 1592 | static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) { | |||
| 1593 | BasicBlock *BB = PN->getParent(); | |||
| 1594 | if (!BB->canSplitPredecessors()) | |||
| 1595 | return false; | |||
| 1596 | // It's not impossible to split EHPad blocks, but if BlockColors already exist | |||
| 1597 | // it require updating BlockColors for all offspring blocks accordingly. By | |||
| 1598 | // skipping such corner case, we can make updating BlockColors after splitting | |||
| 1599 | // predecessor fairly simple. | |||
| 1600 | if (!SafetyInfo->getBlockColors().empty() && BB->getFirstNonPHI()->isEHPad()) | |||
| 1601 | return false; | |||
| 1602 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { | |||
| 1603 | BasicBlock *BBPred = *PI; | |||
| 1604 | if (isa<IndirectBrInst>(BBPred->getTerminator()) || | |||
| 1605 | isa<CallBrInst>(BBPred->getTerminator())) | |||
| 1606 | return false; | |||
| 1607 | } | |||
| 1608 | return true; | |||
| 1609 | } | |||
| 1610 | ||||
| 1611 | static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT, | |||
| 1612 | LoopInfo *LI, const Loop *CurLoop, | |||
| 1613 | LoopSafetyInfo *SafetyInfo, | |||
| 1614 | MemorySSAUpdater *MSSAU) { | |||
| 1615 | #ifndef NDEBUG1 | |||
| 1616 | SmallVector<BasicBlock *, 32> ExitBlocks; | |||
| 1617 | CurLoop->getUniqueExitBlocks(ExitBlocks); | |||
| 1618 | SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), | |||
| 1619 | ExitBlocks.end()); | |||
| 1620 | #endif | |||
| 1621 | BasicBlock *ExitBB = PN->getParent(); | |||
| 1622 | assert(ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block.")((void)0); | |||
| 1623 | ||||
| 1624 | // Split predecessors of the loop exit to make instructions in the loop are | |||
| 1625 | // exposed to exit blocks through trivially replaceable PHIs while keeping the | |||
| 1626 | // loop in the canonical form where each predecessor of each exit block should | |||
| 1627 | // be contained within the loop. For example, this will convert the loop below | |||
| 1628 | // from | |||
| 1629 | // | |||
| 1630 | // LB1: | |||
| 1631 | // %v1 = | |||
| 1632 | // br %LE, %LB2 | |||
| 1633 | // LB2: | |||
| 1634 | // %v2 = | |||
| 1635 | // br %LE, %LB1 | |||
| 1636 | // LE: | |||
| 1637 | // %p = phi [%v1, %LB1], [%v2, %LB2] <-- non-trivially replaceable | |||
| 1638 | // | |||
| 1639 | // to | |||
| 1640 | // | |||
| 1641 | // LB1: | |||
| 1642 | // %v1 = | |||
| 1643 | // br %LE.split, %LB2 | |||
| 1644 | // LB2: | |||
| 1645 | // %v2 = | |||
| 1646 | // br %LE.split2, %LB1 | |||
| 1647 | // LE.split: | |||
| 1648 | // %p1 = phi [%v1, %LB1] <-- trivially replaceable | |||
| 1649 | // br %LE | |||
| 1650 | // LE.split2: | |||
| 1651 | // %p2 = phi [%v2, %LB2] <-- trivially replaceable | |||
| 1652 | // br %LE | |||
| 1653 | // LE: | |||
| 1654 | // %p = phi [%p1, %LE.split], [%p2, %LE.split2] | |||
| 1655 | // | |||
| 1656 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1657 | SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB)); | |||
| 1658 | while (!PredBBs.empty()) { | |||
| 1659 | BasicBlock *PredBB = *PredBBs.begin(); | |||
| 1660 | assert(CurLoop->contains(PredBB) &&((void)0) | |||
| 1661 | "Expect all predecessors are in the loop")((void)0); | |||
| 1662 | if (PN->getBasicBlockIndex(PredBB) >= 0) { | |||
| 1663 | BasicBlock *NewPred = SplitBlockPredecessors( | |||
| 1664 | ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true); | |||
| 1665 | // Since we do not allow splitting EH-block with BlockColors in | |||
| 1666 | // canSplitPredecessors(), we can simply assign predecessor's color to | |||
| 1667 | // the new block. | |||
| 1668 | if (!BlockColors.empty()) | |||
| 1669 | // Grab a reference to the ColorVector to be inserted before getting the | |||
| 1670 | // reference to the vector we are copying because inserting the new | |||
| 1671 | // element in BlockColors might cause the map to be reallocated. | |||
| 1672 | SafetyInfo->copyColors(NewPred, PredBB); | |||
| 1673 | } | |||
| 1674 | PredBBs.remove(PredBB); | |||
| 1675 | } | |||
| 1676 | } | |||
| 1677 | ||||
| 1678 | /// When an instruction is found to only be used outside of the loop, this | |||
| 1679 | /// function moves it to the exit blocks and patches up SSA form as needed. | |||
| 1680 | /// This method is guaranteed to remove the original instruction from its | |||
| 1681 | /// position, and may either delete it or move it to outside of the loop. | |||
| 1682 | /// | |||
| 1683 | static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, | |||
| 1684 | BlockFrequencyInfo *BFI, const Loop *CurLoop, | |||
| 1685 | ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU, | |||
| 1686 | OptimizationRemarkEmitter *ORE) { | |||
| 1687 | bool Changed = false; | |||
| 1688 | LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n")do { } while (false); | |||
| 1689 | ||||
| 1690 | // Iterate over users to be ready for actual sinking. Replace users via | |||
| 1691 | // unreachable blocks with undef and make all user PHIs trivially replaceable. | |||
| 1692 | SmallPtrSet<Instruction *, 8> VisitedUsers; | |||
| 1693 | for (Value::user_iterator UI = I.user_begin(), UE = I.user_end(); UI != UE;) { | |||
| 1694 | auto *User = cast<Instruction>(*UI); | |||
| 1695 | Use &U = UI.getUse(); | |||
| 1696 | ++UI; | |||
| 1697 | ||||
| 1698 | if (VisitedUsers.count(User) || CurLoop->contains(User)) | |||
| 1699 | continue; | |||
| 1700 | ||||
| 1701 | if (!DT->isReachableFromEntry(User->getParent())) { | |||
| 1702 | U = UndefValue::get(I.getType()); | |||
| 1703 | Changed = true; | |||
| 1704 | continue; | |||
| 1705 | } | |||
| 1706 | ||||
| 1707 | // The user must be a PHI node. | |||
| 1708 | PHINode *PN = cast<PHINode>(User); | |||
| 1709 | ||||
| 1710 | // Surprisingly, instructions can be used outside of loops without any | |||
| 1711 | // exits. This can only happen in PHI nodes if the incoming block is | |||
| 1712 | // unreachable. | |||
| 1713 | BasicBlock *BB = PN->getIncomingBlock(U); | |||
| 1714 | if (!DT->isReachableFromEntry(BB)) { | |||
| 1715 | U = UndefValue::get(I.getType()); | |||
| 1716 | Changed = true; | |||
| 1717 | continue; | |||
| 1718 | } | |||
| 1719 | ||||
| 1720 | VisitedUsers.insert(PN); | |||
| 1721 | if (isTriviallyReplaceablePHI(*PN, I)) | |||
| 1722 | continue; | |||
| 1723 | ||||
| 1724 | if (!canSplitPredecessors(PN, SafetyInfo)) | |||
| 1725 | return Changed; | |||
| 1726 | ||||
| 1727 | // Split predecessors of the PHI so that we can make users trivially | |||
| 1728 | // replaceable. | |||
| 1729 | splitPredecessorsOfLoopExit(PN, DT, LI, CurLoop, SafetyInfo, MSSAU); | |||
| 1730 | ||||
| 1731 | // Should rebuild the iterators, as they may be invalidated by | |||
| 1732 | // splitPredecessorsOfLoopExit(). | |||
| 1733 | UI = I.user_begin(); | |||
| 1734 | UE = I.user_end(); | |||
| 1735 | } | |||
| 1736 | ||||
| 1737 | if (VisitedUsers.empty()) | |||
| 1738 | return Changed; | |||
| 1739 | ||||
| 1740 | ORE->emit([&]() { | |||
| 1741 | return OptimizationRemark(DEBUG_TYPE"licm", "InstSunk", &I) | |||
| 1742 | << "sinking " << ore::NV("Inst", &I); | |||
| 1743 | }); | |||
| 1744 | if (isa<LoadInst>(I)) | |||
| 1745 | ++NumMovedLoads; | |||
| 1746 | else if (isa<CallInst>(I)) | |||
| 1747 | ++NumMovedCalls; | |||
| 1748 | ++NumSunk; | |||
| 1749 | ||||
| 1750 | #ifndef NDEBUG1 | |||
| 1751 | SmallVector<BasicBlock *, 32> ExitBlocks; | |||
| 1752 | CurLoop->getUniqueExitBlocks(ExitBlocks); | |||
| 1753 | SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), | |||
| 1754 | ExitBlocks.end()); | |||
| 1755 | #endif | |||
| 1756 | ||||
| 1757 | // Clones of this instruction. Don't create more than one per exit block! | |||
| 1758 | SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies; | |||
| 1759 | ||||
| 1760 | // If this instruction is only used outside of the loop, then all users are | |||
| 1761 | // PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of | |||
| 1762 | // the instruction. | |||
| 1763 | // First check if I is worth sinking for all uses. Sink only when it is worth | |||
| 1764 | // across all uses. | |||
| 1765 | SmallSetVector<User*, 8> Users(I.user_begin(), I.user_end()); | |||
| 1766 | SmallVector<PHINode *, 8> ExitPNs; | |||
| 1767 | for (auto *UI : Users) { | |||
| 1768 | auto *User = cast<Instruction>(UI); | |||
| 1769 | ||||
| 1770 | if (CurLoop->contains(User)) | |||
| 1771 | continue; | |||
| 1772 | ||||
| 1773 | PHINode *PN = cast<PHINode>(User); | |||
| 1774 | assert(ExitBlockSet.count(PN->getParent()) &&((void)0) | |||
| 1775 | "The LCSSA PHI is not in an exit block!")((void)0); | |||
| 1776 | if (!worthSinkOrHoistInst(I, PN->getParent(), ORE, BFI)) { | |||
| 1777 | return Changed; | |||
| 1778 | } | |||
| 1779 | ||||
| 1780 | ExitPNs.push_back(PN); | |||
| 1781 | } | |||
| 1782 | ||||
| 1783 | for (auto *PN : ExitPNs) { | |||
| 1784 | ||||
| 1785 | // The PHI must be trivially replaceable. | |||
| 1786 | Instruction *New = sinkThroughTriviallyReplaceablePHI( | |||
| 1787 | PN, &I, LI, SunkCopies, SafetyInfo, CurLoop, MSSAU); | |||
| 1788 | PN->replaceAllUsesWith(New); | |||
| 1789 | eraseInstruction(*PN, *SafetyInfo, nullptr, nullptr); | |||
| 1790 | Changed = true; | |||
| 1791 | } | |||
| 1792 | return Changed; | |||
| 1793 | } | |||
| 1794 | ||||
| 1795 | /// When an instruction is found to only use loop invariant operands that | |||
| 1796 | /// is safe to hoist, this instruction is called to do the dirty work. | |||
| 1797 | /// | |||
| 1798 | static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, | |||
| 1799 | BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, | |||
| 1800 | MemorySSAUpdater *MSSAU, ScalarEvolution *SE, | |||
| 1801 | OptimizationRemarkEmitter *ORE) { | |||
| 1802 | LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getNameOrAsOperand() << ": "do { } while (false) | |||
| 1803 | << I << "\n")do { } while (false); | |||
| 1804 | ORE->emit([&]() { | |||
| 1805 | return OptimizationRemark(DEBUG_TYPE"licm", "Hoisted", &I) << "hoisting " | |||
| 1806 | << ore::NV("Inst", &I); | |||
| 1807 | }); | |||
| 1808 | ||||
| 1809 | // Metadata can be dependent on conditions we are hoisting above. | |||
| 1810 | // Conservatively strip all metadata on the instruction unless we were | |||
| 1811 | // guaranteed to execute I if we entered the loop, in which case the metadata | |||
| 1812 | // is valid in the loop preheader. | |||
| 1813 | // Similarly, If I is a call and it is not guaranteed to execute in the loop, | |||
| 1814 | // then moving to the preheader means we should strip attributes on the call | |||
| 1815 | // that can cause UB since we may be hoisting above conditions that allowed | |||
| 1816 | // inferring those attributes. They may not be valid at the preheader. | |||
| 1817 | if ((I.hasMetadataOtherThanDebugLoc() || isa<CallInst>(I)) && | |||
| 1818 | // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning | |||
| 1819 | // time in isGuaranteedToExecute if we don't actually have anything to | |||
| 1820 | // drop. It is a compile time optimization, not required for correctness. | |||
| 1821 | !SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop)) | |||
| 1822 | I.dropUndefImplyingAttrsAndUnknownMetadata(); | |||
| 1823 | ||||
| 1824 | if (isa<PHINode>(I)) | |||
| 1825 | // Move the new node to the end of the phi list in the destination block. | |||
| 1826 | moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU, SE); | |||
| 1827 | else | |||
| 1828 | // Move the new node to the destination block, before its terminator. | |||
| 1829 | moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU, SE); | |||
| 1830 | ||||
| 1831 | I.updateLocationAfterHoist(); | |||
| 1832 | ||||
| 1833 | if (isa<LoadInst>(I)) | |||
| 1834 | ++NumMovedLoads; | |||
| 1835 | else if (isa<CallInst>(I)) | |||
| 1836 | ++NumMovedCalls; | |||
| 1837 | ++NumHoisted; | |||
| 1838 | } | |||
| 1839 | ||||
| 1840 | /// Only sink or hoist an instruction if it is not a trapping instruction, | |||
| 1841 | /// or if the instruction is known not to trap when moved to the preheader. | |||
| 1842 | /// or if it is a trapping instruction and is guaranteed to execute. | |||
| 1843 | static bool isSafeToExecuteUnconditionally(Instruction &Inst, | |||
| 1844 | const DominatorTree *DT, | |||
| 1845 | const TargetLibraryInfo *TLI, | |||
| 1846 | const Loop *CurLoop, | |||
| 1847 | const LoopSafetyInfo *SafetyInfo, | |||
| 1848 | OptimizationRemarkEmitter *ORE, | |||
| 1849 | const Instruction *CtxI) { | |||
| 1850 | if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT, TLI)) | |||
| 1851 | return true; | |||
| 1852 | ||||
| 1853 | bool GuaranteedToExecute = | |||
| 1854 | SafetyInfo->isGuaranteedToExecute(Inst, DT, CurLoop); | |||
| 1855 | ||||
| 1856 | if (!GuaranteedToExecute) { | |||
| 1857 | auto *LI = dyn_cast<LoadInst>(&Inst); | |||
| 1858 | if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand())) | |||
| 1859 | ORE->emit([&]() { | |||
| 1860 | return OptimizationRemarkMissed( | |||
| 1861 | DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressCondExecuted", LI) | |||
| 1862 | << "failed to hoist load with loop-invariant address " | |||
| 1863 | "because load is conditionally executed"; | |||
| 1864 | }); | |||
| 1865 | } | |||
| 1866 | ||||
| 1867 | return GuaranteedToExecute; | |||
| 1868 | } | |||
| 1869 | ||||
| 1870 | namespace { | |||
| 1871 | class LoopPromoter : public LoadAndStorePromoter { | |||
| 1872 | Value *SomePtr; // Designated pointer to store to. | |||
| 1873 | const SmallSetVector<Value *, 8> &PointerMustAliases; | |||
| 1874 | SmallVectorImpl<BasicBlock *> &LoopExitBlocks; | |||
| 1875 | SmallVectorImpl<Instruction *> &LoopInsertPts; | |||
| 1876 | SmallVectorImpl<MemoryAccess *> &MSSAInsertPts; | |||
| 1877 | PredIteratorCache &PredCache; | |||
| 1878 | AliasSetTracker *AST; | |||
| 1879 | MemorySSAUpdater *MSSAU; | |||
| 1880 | LoopInfo &LI; | |||
| 1881 | DebugLoc DL; | |||
| 1882 | int Alignment; | |||
| 1883 | bool UnorderedAtomic; | |||
| 1884 | AAMDNodes AATags; | |||
| 1885 | ICFLoopSafetyInfo &SafetyInfo; | |||
| 1886 | ||||
| 1887 | // We're about to add a use of V in a loop exit block. Insert an LCSSA phi | |||
| 1888 | // (if legal) if doing so would add an out-of-loop use to an instruction | |||
| 1889 | // defined in-loop. | |||
| 1890 | Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const { | |||
| 1891 | if (!LI.wouldBeOutOfLoopUseRequiringLCSSA(V, BB)) | |||
| 1892 | return V; | |||
| 1893 | ||||
| 1894 | Instruction *I = cast<Instruction>(V); | |||
| 1895 | // We need to create an LCSSA PHI node for the incoming value and | |||
| 1896 | // store that. | |||
| 1897 | PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB), | |||
| 1898 | I->getName() + ".lcssa", &BB->front()); | |||
| 1899 | for (BasicBlock *Pred : PredCache.get(BB)) | |||
| 1900 | PN->addIncoming(I, Pred); | |||
| 1901 | return PN; | |||
| 1902 | } | |||
| 1903 | ||||
| 1904 | public: | |||
| 1905 | LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S, | |||
| 1906 | const SmallSetVector<Value *, 8> &PMA, | |||
| 1907 | SmallVectorImpl<BasicBlock *> &LEB, | |||
| 1908 | SmallVectorImpl<Instruction *> &LIP, | |||
| 1909 | SmallVectorImpl<MemoryAccess *> &MSSAIP, PredIteratorCache &PIC, | |||
| 1910 | AliasSetTracker *ast, MemorySSAUpdater *MSSAU, LoopInfo &li, | |||
| 1911 | DebugLoc dl, int alignment, bool UnorderedAtomic, | |||
| 1912 | const AAMDNodes &AATags, ICFLoopSafetyInfo &SafetyInfo) | |||
| 1913 | : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA), | |||
| 1914 | LoopExitBlocks(LEB), LoopInsertPts(LIP), MSSAInsertPts(MSSAIP), | |||
| 1915 | PredCache(PIC), AST(ast), MSSAU(MSSAU), LI(li), DL(std::move(dl)), | |||
| 1916 | Alignment(alignment), UnorderedAtomic(UnorderedAtomic), AATags(AATags), | |||
| 1917 | SafetyInfo(SafetyInfo) {} | |||
| 1918 | ||||
| 1919 | bool isInstInList(Instruction *I, | |||
| 1920 | const SmallVectorImpl<Instruction *> &) const override { | |||
| 1921 | Value *Ptr; | |||
| 1922 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) | |||
| 1923 | Ptr = LI->getOperand(0); | |||
| 1924 | else | |||
| 1925 | Ptr = cast<StoreInst>(I)->getPointerOperand(); | |||
| 1926 | return PointerMustAliases.count(Ptr); | |||
| 1927 | } | |||
| 1928 | ||||
| 1929 | void doExtraRewritesBeforeFinalDeletion() override { | |||
| 1930 | // Insert stores after in the loop exit blocks. Each exit block gets a | |||
| 1931 | // store of the live-out values that feed them. Since we've already told | |||
| 1932 | // the SSA updater about the defs in the loop and the preheader | |||
| 1933 | // definition, it is all set and we can start using it. | |||
| 1934 | for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) { | |||
| 1935 | BasicBlock *ExitBlock = LoopExitBlocks[i]; | |||
| 1936 | Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); | |||
| 1937 | LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock); | |||
| 1938 | Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock); | |||
| 1939 | Instruction *InsertPos = LoopInsertPts[i]; | |||
| 1940 | StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos); | |||
| 1941 | if (UnorderedAtomic) | |||
| 1942 | NewSI->setOrdering(AtomicOrdering::Unordered); | |||
| 1943 | NewSI->setAlignment(Align(Alignment)); | |||
| 1944 | NewSI->setDebugLoc(DL); | |||
| 1945 | if (AATags) | |||
| 1946 | NewSI->setAAMetadata(AATags); | |||
| 1947 | ||||
| 1948 | if (MSSAU) { | |||
| 1949 | MemoryAccess *MSSAInsertPoint = MSSAInsertPts[i]; | |||
| 1950 | MemoryAccess *NewMemAcc; | |||
| 1951 | if (!MSSAInsertPoint) { | |||
| 1952 | NewMemAcc = MSSAU->createMemoryAccessInBB( | |||
| 1953 | NewSI, nullptr, NewSI->getParent(), MemorySSA::Beginning); | |||
| 1954 | } else { | |||
| 1955 | NewMemAcc = | |||
| 1956 | MSSAU->createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint); | |||
| 1957 | } | |||
| 1958 | MSSAInsertPts[i] = NewMemAcc; | |||
| 1959 | MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true); | |||
| 1960 | // FIXME: true for safety, false may still be correct. | |||
| 1961 | } | |||
| 1962 | } | |||
| 1963 | } | |||
| 1964 | ||||
| 1965 | void replaceLoadWithValue(LoadInst *LI, Value *V) const override { | |||
| 1966 | // Update alias analysis. | |||
| 1967 | if (AST) | |||
| 1968 | AST->copyValue(LI, V); | |||
| 1969 | } | |||
| 1970 | void instructionDeleted(Instruction *I) const override { | |||
| 1971 | SafetyInfo.removeInstruction(I); | |||
| 1972 | if (AST) | |||
| 1973 | AST->deleteValue(I); | |||
| 1974 | if (MSSAU) | |||
| 1975 | MSSAU->removeMemoryAccess(I); | |||
| 1976 | } | |||
| 1977 | }; | |||
| 1978 | ||||
| 1979 | bool isNotCapturedBeforeOrInLoop(const Value *V, const Loop *L, | |||
| 1980 | DominatorTree *DT) { | |||
| 1981 | // We can perform the captured-before check against any instruction in the | |||
| 1982 | // loop header, as the loop header is reachable from any instruction inside | |||
| 1983 | // the loop. | |||
| 1984 | // TODO: ReturnCaptures=true shouldn't be necessary here. | |||
| 1985 | return !PointerMayBeCapturedBefore(V, /* ReturnCaptures */ true, | |||
| 1986 | /* StoreCaptures */ true, | |||
| 1987 | L->getHeader()->getTerminator(), DT); | |||
| 1988 | } | |||
| 1989 | ||||
| 1990 | /// Return true iff we can prove that a caller of this function can not inspect | |||
| 1991 | /// the contents of the provided object in a well defined program. | |||
| 1992 | bool isKnownNonEscaping(Value *Object, const Loop *L, | |||
| 1993 | const TargetLibraryInfo *TLI, DominatorTree *DT) { | |||
| 1994 | if (isa<AllocaInst>(Object)) | |||
| 1995 | // Since the alloca goes out of scope, we know the caller can't retain a | |||
| 1996 | // reference to it and be well defined. Thus, we don't need to check for | |||
| 1997 | // capture. | |||
| 1998 | return true; | |||
| 1999 | ||||
| 2000 | // For all other objects we need to know that the caller can't possibly | |||
| 2001 | // have gotten a reference to the object. There are two components of | |||
| 2002 | // that: | |||
| 2003 | // 1) Object can't be escaped by this function. This is what | |||
| 2004 | // PointerMayBeCaptured checks. | |||
| 2005 | // 2) Object can't have been captured at definition site. For this, we | |||
| 2006 | // need to know the return value is noalias. At the moment, we use a | |||
| 2007 | // weaker condition and handle only AllocLikeFunctions (which are | |||
| 2008 | // known to be noalias). TODO | |||
| 2009 | return isAllocLikeFn(Object, TLI) && | |||
| 2010 | isNotCapturedBeforeOrInLoop(Object, L, DT); | |||
| 2011 | } | |||
| 2012 | ||||
| 2013 | } // namespace | |||
| 2014 | ||||
| 2015 | /// Try to promote memory values to scalars by sinking stores out of the | |||
| 2016 | /// loop and moving loads to before the loop. We do this by looping over | |||
| 2017 | /// the stores in the loop, looking for stores to Must pointers which are | |||
| 2018 | /// loop invariant. | |||
| 2019 | /// | |||
| 2020 | bool llvm::promoteLoopAccessesToScalars( | |||
| 2021 | const SmallSetVector<Value *, 8> &PointerMustAliases, | |||
| 2022 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | |||
| 2023 | SmallVectorImpl<Instruction *> &InsertPts, | |||
| 2024 | SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC, | |||
| 2025 | LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI, | |||
| 2026 | Loop *CurLoop, AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, | |||
| 2027 | ICFLoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE) { | |||
| 2028 | // Verify inputs. | |||
| 2029 | assert(LI != nullptr && DT != nullptr && CurLoop != nullptr &&((void)0) | |||
| 2030 | SafetyInfo != nullptr &&((void)0) | |||
| 2031 | "Unexpected Input to promoteLoopAccessesToScalars")((void)0); | |||
| 2032 | ||||
| 2033 | Value *SomePtr = *PointerMustAliases.begin(); | |||
| 2034 | BasicBlock *Preheader = CurLoop->getLoopPreheader(); | |||
| 2035 | ||||
| 2036 | // It is not safe to promote a load/store from the loop if the load/store is | |||
| 2037 | // conditional. For example, turning: | |||
| 2038 | // | |||
| 2039 | // for () { if (c) *P += 1; } | |||
| 2040 | // | |||
| 2041 | // into: | |||
| 2042 | // | |||
| 2043 | // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; | |||
| 2044 | // | |||
| 2045 | // is not safe, because *P may only be valid to access if 'c' is true. | |||
| 2046 | // | |||
| 2047 | // The safety property divides into two parts: | |||
| 2048 | // p1) The memory may not be dereferenceable on entry to the loop. In this | |||
| 2049 | // case, we can't insert the required load in the preheader. | |||
| 2050 | // p2) The memory model does not allow us to insert a store along any dynamic | |||
| 2051 | // path which did not originally have one. | |||
| 2052 | // | |||
| 2053 | // If at least one store is guaranteed to execute, both properties are | |||
| 2054 | // satisfied, and promotion is legal. | |||
| 2055 | // | |||
| 2056 | // This, however, is not a necessary condition. Even if no store/load is | |||
| 2057 | // guaranteed to execute, we can still establish these properties. | |||
| 2058 | // We can establish (p1) by proving that hoisting the load into the preheader | |||
| 2059 | // is safe (i.e. proving dereferenceability on all paths through the loop). We | |||
| 2060 | // can use any access within the alias set to prove dereferenceability, | |||
| 2061 | // since they're all must alias. | |||
| 2062 | // | |||
| 2063 | // There are two ways establish (p2): | |||
| 2064 | // a) Prove the location is thread-local. In this case the memory model | |||
| 2065 | // requirement does not apply, and stores are safe to insert. | |||
| 2066 | // b) Prove a store dominates every exit block. In this case, if an exit | |||
| 2067 | // blocks is reached, the original dynamic path would have taken us through | |||
| 2068 | // the store, so inserting a store into the exit block is safe. Note that this | |||
| 2069 | // is different from the store being guaranteed to execute. For instance, | |||
| 2070 | // if an exception is thrown on the first iteration of the loop, the original | |||
| 2071 | // store is never executed, but the exit blocks are not executed either. | |||
| 2072 | ||||
| 2073 | bool DereferenceableInPH = false; | |||
| 2074 | bool SafeToInsertStore = false; | |||
| 2075 | ||||
| 2076 | SmallVector<Instruction *, 64> LoopUses; | |||
| 2077 | ||||
| 2078 | // We start with an alignment of one and try to find instructions that allow | |||
| 2079 | // us to prove better alignment. | |||
| 2080 | Align Alignment; | |||
| 2081 | // Keep track of which types of access we see | |||
| 2082 | bool SawUnorderedAtomic = false; | |||
| 2083 | bool SawNotAtomic = false; | |||
| 2084 | AAMDNodes AATags; | |||
| 2085 | ||||
| 2086 | const DataLayout &MDL = Preheader->getModule()->getDataLayout(); | |||
| 2087 | ||||
| 2088 | bool IsKnownThreadLocalObject = false; | |||
| 2089 | if (SafetyInfo->anyBlockMayThrow()) { | |||
| 2090 | // If a loop can throw, we have to insert a store along each unwind edge. | |||
| 2091 | // That said, we can't actually make the unwind edge explicit. Therefore, | |||
| 2092 | // we have to prove that the store is dead along the unwind edge. We do | |||
| 2093 | // this by proving that the caller can't have a reference to the object | |||
| 2094 | // after return and thus can't possibly load from the object. | |||
| 2095 | Value *Object = getUnderlyingObject(SomePtr); | |||
| 2096 | if (!isKnownNonEscaping(Object, CurLoop, TLI, DT)) | |||
| 2097 | return false; | |||
| 2098 | // Subtlety: Alloca's aren't visible to callers, but *are* potentially | |||
| 2099 | // visible to other threads if captured and used during their lifetimes. | |||
| 2100 | IsKnownThreadLocalObject = !isa<AllocaInst>(Object); | |||
| 2101 | } | |||
| 2102 | ||||
| 2103 | // Check that all of the pointers in the alias set have the same type. We | |||
| 2104 | // cannot (yet) promote a memory location that is loaded and stored in | |||
| 2105 | // different sizes. While we are at it, collect alignment and AA info. | |||
| 2106 | for (Value *ASIV : PointerMustAliases) { | |||
| 2107 | // Check that all of the pointers in the alias set have the same type. We | |||
| 2108 | // cannot (yet) promote a memory location that is loaded and stored in | |||
| 2109 | // different sizes. | |||
| 2110 | if (SomePtr->getType() != ASIV->getType()) | |||
| 2111 | return false; | |||
| 2112 | ||||
| 2113 | for (User *U : ASIV->users()) { | |||
| 2114 | // Ignore instructions that are outside the loop. | |||
| 2115 | Instruction *UI = dyn_cast<Instruction>(U); | |||
| 2116 | if (!UI || !CurLoop->contains(UI)) | |||
| 2117 | continue; | |||
| 2118 | ||||
| 2119 | // If there is an non-load/store instruction in the loop, we can't promote | |||
| 2120 | // it. | |||
| 2121 | if (LoadInst *Load = dyn_cast<LoadInst>(UI)) { | |||
| 2122 | if (!Load->isUnordered()) | |||
| 2123 | return false; | |||
| 2124 | ||||
| 2125 | SawUnorderedAtomic |= Load->isAtomic(); | |||
| 2126 | SawNotAtomic |= !Load->isAtomic(); | |||
| 2127 | ||||
| 2128 | Align InstAlignment = Load->getAlign(); | |||
| 2129 | ||||
| 2130 | // Note that proving a load safe to speculate requires proving | |||
| 2131 | // sufficient alignment at the target location. Proving it guaranteed | |||
| 2132 | // to execute does as well. Thus we can increase our guaranteed | |||
| 2133 | // alignment as well. | |||
| 2134 | if (!DereferenceableInPH || (InstAlignment > Alignment)) | |||
| 2135 | if (isSafeToExecuteUnconditionally(*Load, DT, TLI, CurLoop, | |||
| 2136 | SafetyInfo, ORE, | |||
| 2137 | Preheader->getTerminator())) { | |||
| 2138 | DereferenceableInPH = true; | |||
| 2139 | Alignment = std::max(Alignment, InstAlignment); | |||
| 2140 | } | |||
| 2141 | } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) { | |||
| 2142 | // Stores *of* the pointer are not interesting, only stores *to* the | |||
| 2143 | // pointer. | |||
| 2144 | if (UI->getOperand(1) != ASIV) | |||
| 2145 | continue; | |||
| 2146 | if (!Store->isUnordered()) | |||
| 2147 | return false; | |||
| 2148 | ||||
| 2149 | SawUnorderedAtomic |= Store->isAtomic(); | |||
| 2150 | SawNotAtomic |= !Store->isAtomic(); | |||
| 2151 | ||||
| 2152 | // If the store is guaranteed to execute, both properties are satisfied. | |||
| 2153 | // We may want to check if a store is guaranteed to execute even if we | |||
| 2154 | // already know that promotion is safe, since it may have higher | |||
| 2155 | // alignment than any other guaranteed stores, in which case we can | |||
| 2156 | // raise the alignment on the promoted store. | |||
| 2157 | Align InstAlignment = Store->getAlign(); | |||
| 2158 | ||||
| 2159 | if (!DereferenceableInPH || !SafeToInsertStore || | |||
| 2160 | (InstAlignment > Alignment)) { | |||
| 2161 | if (SafetyInfo->isGuaranteedToExecute(*UI, DT, CurLoop)) { | |||
| 2162 | DereferenceableInPH = true; | |||
| 2163 | SafeToInsertStore = true; | |||
| 2164 | Alignment = std::max(Alignment, InstAlignment); | |||
| 2165 | } | |||
| 2166 | } | |||
| 2167 | ||||
| 2168 | // If a store dominates all exit blocks, it is safe to sink. | |||
| 2169 | // As explained above, if an exit block was executed, a dominating | |||
| 2170 | // store must have been executed at least once, so we are not | |||
| 2171 | // introducing stores on paths that did not have them. | |||
| 2172 | // Note that this only looks at explicit exit blocks. If we ever | |||
| 2173 | // start sinking stores into unwind edges (see above), this will break. | |||
| 2174 | if (!SafeToInsertStore) | |||
| 2175 | SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) { | |||
| 2176 | return DT->dominates(Store->getParent(), Exit); | |||
| 2177 | }); | |||
| 2178 | ||||
| 2179 | // If the store is not guaranteed to execute, we may still get | |||
| 2180 | // deref info through it. | |||
| 2181 | if (!DereferenceableInPH) { | |||
| 2182 | DereferenceableInPH = isDereferenceableAndAlignedPointer( | |||
| 2183 | Store->getPointerOperand(), Store->getValueOperand()->getType(), | |||
| 2184 | Store->getAlign(), MDL, Preheader->getTerminator(), DT, TLI); | |||
| 2185 | } | |||
| 2186 | } else | |||
| 2187 | return false; // Not a load or store. | |||
| 2188 | ||||
| 2189 | // Merge the AA tags. | |||
| 2190 | if (LoopUses.empty()) { | |||
| 2191 | // On the first load/store, just take its AA tags. | |||
| 2192 | UI->getAAMetadata(AATags); | |||
| 2193 | } else if (AATags) { | |||
| 2194 | UI->getAAMetadata(AATags, /* Merge = */ true); | |||
| 2195 | } | |||
| 2196 | ||||
| 2197 | LoopUses.push_back(UI); | |||
| 2198 | } | |||
| 2199 | } | |||
| 2200 | ||||
| 2201 | // If we found both an unordered atomic instruction and a non-atomic memory | |||
| 2202 | // access, bail. We can't blindly promote non-atomic to atomic since we | |||
| 2203 | // might not be able to lower the result. We can't downgrade since that | |||
| 2204 | // would violate memory model. Also, align 0 is an error for atomics. | |||
| 2205 | if (SawUnorderedAtomic && SawNotAtomic) | |||
| 2206 | return false; | |||
| 2207 | ||||
| 2208 | // If we're inserting an atomic load in the preheader, we must be able to | |||
| 2209 | // lower it. We're only guaranteed to be able to lower naturally aligned | |||
| 2210 | // atomics. | |||
| 2211 | auto *SomePtrElemType = SomePtr->getType()->getPointerElementType(); | |||
| 2212 | if (SawUnorderedAtomic && | |||
| 2213 | Alignment < MDL.getTypeStoreSize(SomePtrElemType)) | |||
| 2214 | return false; | |||
| 2215 | ||||
| 2216 | // If we couldn't prove we can hoist the load, bail. | |||
| 2217 | if (!DereferenceableInPH) | |||
| 2218 | return false; | |||
| 2219 | ||||
| 2220 | // We know we can hoist the load, but don't have a guaranteed store. | |||
| 2221 | // Check whether the location is thread-local. If it is, then we can insert | |||
| 2222 | // stores along paths which originally didn't have them without violating the | |||
| 2223 | // memory model. | |||
| 2224 | if (!SafeToInsertStore) { | |||
| 2225 | if (IsKnownThreadLocalObject) | |||
| 2226 | SafeToInsertStore = true; | |||
| 2227 | else { | |||
| 2228 | Value *Object = getUnderlyingObject(SomePtr); | |||
| 2229 | SafeToInsertStore = | |||
| 2230 | (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) && | |||
| 2231 | isNotCapturedBeforeOrInLoop(Object, CurLoop, DT); | |||
| 2232 | } | |||
| 2233 | } | |||
| 2234 | ||||
| 2235 | // If we've still failed to prove we can sink the store, give up. | |||
| 2236 | if (!SafeToInsertStore) | |||
| 2237 | return false; | |||
| 2238 | ||||
| 2239 | // Otherwise, this is safe to promote, lets do it! | |||
| 2240 | LLVM_DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtrdo { } while (false) | |||
| 2241 | << '\n')do { } while (false); | |||
| 2242 | ORE->emit([&]() { | |||
| 2243 | return OptimizationRemark(DEBUG_TYPE"licm", "PromoteLoopAccessesToScalar", | |||
| 2244 | LoopUses[0]) | |||
| 2245 | << "Moving accesses to memory location out of the loop"; | |||
| 2246 | }); | |||
| 2247 | ++NumPromoted; | |||
| 2248 | ||||
| 2249 | // Look at all the loop uses, and try to merge their locations. | |||
| 2250 | std::vector<const DILocation *> LoopUsesLocs; | |||
| 2251 | for (auto U : LoopUses) | |||
| 2252 | LoopUsesLocs.push_back(U->getDebugLoc().get()); | |||
| 2253 | auto DL = DebugLoc(DILocation::getMergedLocations(LoopUsesLocs)); | |||
| 2254 | ||||
| 2255 | // We use the SSAUpdater interface to insert phi nodes as required. | |||
| 2256 | SmallVector<PHINode *, 16> NewPHIs; | |||
| 2257 | SSAUpdater SSA(&NewPHIs); | |||
| 2258 | LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks, | |||
| 2259 | InsertPts, MSSAInsertPts, PIC, CurAST, MSSAU, *LI, DL, | |||
| 2260 | Alignment.value(), SawUnorderedAtomic, AATags, | |||
| 2261 | *SafetyInfo); | |||
| 2262 | ||||
| 2263 | // Set up the preheader to have a definition of the value. It is the live-out | |||
| 2264 | // value from the preheader that uses in the loop will use. | |||
| 2265 | LoadInst *PreheaderLoad = new LoadInst( | |||
| 2266 | SomePtr->getType()->getPointerElementType(), SomePtr, | |||
| 2267 | SomePtr->getName() + ".promoted", Preheader->getTerminator()); | |||
| 2268 | if (SawUnorderedAtomic) | |||
| 2269 | PreheaderLoad->setOrdering(AtomicOrdering::Unordered); | |||
| 2270 | PreheaderLoad->setAlignment(Alignment); | |||
| 2271 | PreheaderLoad->setDebugLoc(DebugLoc()); | |||
| 2272 | if (AATags) | |||
| 2273 | PreheaderLoad->setAAMetadata(AATags); | |||
| 2274 | SSA.AddAvailableValue(Preheader, PreheaderLoad); | |||
| 2275 | ||||
| 2276 | if (MSSAU) { | |||
| 2277 | MemoryAccess *PreheaderLoadMemoryAccess = MSSAU->createMemoryAccessInBB( | |||
| 2278 | PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End); | |||
| 2279 | MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess); | |||
| 2280 | MSSAU->insertUse(NewMemUse, /*RenameUses=*/true); | |||
| 2281 | } | |||
| 2282 | ||||
| 2283 | if (MSSAU && VerifyMemorySSA) | |||
| 2284 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 2285 | // Rewrite all the loads in the loop and remember all the definitions from | |||
| 2286 | // stores in the loop. | |||
| 2287 | Promoter.run(LoopUses); | |||
| 2288 | ||||
| 2289 | if (MSSAU && VerifyMemorySSA) | |||
| 2290 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 2291 | // If the SSAUpdater didn't use the load in the preheader, just zap it now. | |||
| 2292 | if (PreheaderLoad->use_empty()) | |||
| 2293 | eraseInstruction(*PreheaderLoad, *SafetyInfo, CurAST, MSSAU); | |||
| 2294 | ||||
| 2295 | return true; | |||
| 2296 | } | |||
| 2297 | ||||
| 2298 | static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L, | |||
| 2299 | function_ref<void(Instruction *)> Fn) { | |||
| 2300 | for (const BasicBlock *BB : L->blocks()) | |||
| 2301 | if (const auto *Accesses = MSSA->getBlockAccesses(BB)) | |||
| 2302 | for (const auto &Access : *Accesses) | |||
| 2303 | if (const auto *MUD = dyn_cast<MemoryUseOrDef>(&Access)) | |||
| 2304 | Fn(MUD->getMemoryInst()); | |||
| 2305 | } | |||
| 2306 | ||||
| 2307 | static SmallVector<SmallSetVector<Value *, 8>, 0> | |||
| 2308 | collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L) { | |||
| 2309 | AliasSetTracker AST(*AA); | |||
| 2310 | ||||
| 2311 | auto IsPotentiallyPromotable = [L](const Instruction *I) { | |||
| 2312 | if (const auto *SI = dyn_cast<StoreInst>(I)) | |||
| 2313 | return L->isLoopInvariant(SI->getPointerOperand()); | |||
| 2314 | if (const auto *LI = dyn_cast<LoadInst>(I)) | |||
| 2315 | return L->isLoopInvariant(LI->getPointerOperand()); | |||
| 2316 | return false; | |||
| 2317 | }; | |||
| 2318 | ||||
| 2319 | // Populate AST with potentially promotable accesses and remove them from | |||
| 2320 | // MaybePromotable, so they will not be checked again on the next iteration. | |||
| 2321 | SmallPtrSet<Value *, 16> AttemptingPromotion; | |||
| 2322 | foreachMemoryAccess(MSSA, L, [&](Instruction *I) { | |||
| 2323 | if (IsPotentiallyPromotable(I)) { | |||
| 2324 | AttemptingPromotion.insert(I); | |||
| 2325 | AST.add(I); | |||
| 2326 | } | |||
| 2327 | }); | |||
| 2328 | ||||
| 2329 | // We're only interested in must-alias sets that contain a mod. | |||
| 2330 | SmallVector<const AliasSet *, 8> Sets; | |||
| 2331 | for (AliasSet &AS : AST) | |||
| 2332 | if (!AS.isForwardingAliasSet() && AS.isMod() && AS.isMustAlias()) | |||
| 2333 | Sets.push_back(&AS); | |||
| 2334 | ||||
| 2335 | if (Sets.empty()) | |||
| 2336 | return {}; // Nothing to promote... | |||
| 2337 | ||||
| 2338 | // Discard any sets for which there is an aliasing non-promotable access. | |||
| 2339 | foreachMemoryAccess(MSSA, L, [&](Instruction *I) { | |||
| 2340 | if (AttemptingPromotion.contains(I)) | |||
| 2341 | return; | |||
| 2342 | ||||
| 2343 | llvm::erase_if(Sets, [&](const AliasSet *AS) { | |||
| 2344 | return AS->aliasesUnknownInst(I, *AA); | |||
| 2345 | }); | |||
| 2346 | }); | |||
| 2347 | ||||
| 2348 | SmallVector<SmallSetVector<Value *, 8>, 0> Result; | |||
| 2349 | for (const AliasSet *Set : Sets) { | |||
| 2350 | SmallSetVector<Value *, 8> PointerMustAliases; | |||
| 2351 | for (const auto &ASI : *Set) | |||
| 2352 | PointerMustAliases.insert(ASI.getValue()); | |||
| 2353 | Result.push_back(std::move(PointerMustAliases)); | |||
| 2354 | } | |||
| 2355 | ||||
| 2356 | return Result; | |||
| 2357 | } | |||
| 2358 | ||||
| 2359 | /// Returns an owning pointer to an alias set which incorporates aliasing info | |||
| 2360 | /// from L and all subloops of L. | |||
| 2361 | std::unique_ptr<AliasSetTracker> | |||
| 2362 | LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI, | |||
| 2363 | AAResults *AA) { | |||
| 2364 | auto CurAST = std::make_unique<AliasSetTracker>(*AA); | |||
| 2365 | ||||
| 2366 | // Add everything from all the sub loops. | |||
| 2367 | for (Loop *InnerL : L->getSubLoops()) | |||
| 2368 | for (BasicBlock *BB : InnerL->blocks()) | |||
| 2369 | CurAST->add(*BB); | |||
| 2370 | ||||
| 2371 | // And merge in this loop (without anything from inner loops). | |||
| 2372 | for (BasicBlock *BB : L->blocks()) | |||
| 2373 | if (LI->getLoopFor(BB) == L) | |||
| 2374 | CurAST->add(*BB); | |||
| 2375 | ||||
| 2376 | return CurAST; | |||
| 2377 | } | |||
| 2378 | ||||
| 2379 | static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, | |||
| 2380 | AliasSetTracker *CurAST, Loop *CurLoop, | |||
| 2381 | AAResults *AA) { | |||
| 2382 | // First check to see if any of the basic blocks in CurLoop invalidate *V. | |||
| 2383 | bool isInvalidatedAccordingToAST = CurAST->getAliasSetFor(MemLoc).isMod(); | |||
| 2384 | ||||
| 2385 | if (!isInvalidatedAccordingToAST || !LICMN2Theshold) | |||
| 2386 | return isInvalidatedAccordingToAST; | |||
| 2387 | ||||
| 2388 | // Check with a diagnostic analysis if we can refine the information above. | |||
| 2389 | // This is to identify the limitations of using the AST. | |||
| 2390 | // The alias set mechanism used by LICM has a major weakness in that it | |||
| 2391 | // combines all things which may alias into a single set *before* asking | |||
| 2392 | // modref questions. As a result, a single readonly call within a loop will | |||
| 2393 | // collapse all loads and stores into a single alias set and report | |||
| 2394 | // invalidation if the loop contains any store. For example, readonly calls | |||
| 2395 | // with deopt states have this form and create a general alias set with all | |||
| 2396 | // loads and stores. In order to get any LICM in loops containing possible | |||
| 2397 | // deopt states we need a more precise invalidation of checking the mod ref | |||
| 2398 | // info of each instruction within the loop and LI. This has a complexity of | |||
| 2399 | // O(N^2), so currently, it is used only as a diagnostic tool since the | |||
| 2400 | // default value of LICMN2Threshold is zero. | |||
| 2401 | ||||
| 2402 | // Don't look at nested loops. | |||
| 2403 | if (CurLoop->begin() != CurLoop->end()) | |||
| 2404 | return true; | |||
| 2405 | ||||
| 2406 | int N = 0; | |||
| 2407 | for (BasicBlock *BB : CurLoop->getBlocks()) | |||
| 2408 | for (Instruction &I : *BB) { | |||
| 2409 | if (N >= LICMN2Theshold) { | |||
| 2410 | LLVM_DEBUG(dbgs() << "Alasing N2 threshold exhausted for "do { } while (false) | |||
| 2411 | << *(MemLoc.Ptr) << "\n")do { } while (false); | |||
| 2412 | return true; | |||
| 2413 | } | |||
| 2414 | N++; | |||
| 2415 | auto Res = AA->getModRefInfo(&I, MemLoc); | |||
| 2416 | if (isModSet(Res)) { | |||
| 2417 | LLVM_DEBUG(dbgs() << "Aliasing failed on " << I << " for "do { } while (false) | |||
| 2418 | << *(MemLoc.Ptr) << "\n")do { } while (false); | |||
| 2419 | return true; | |||
| 2420 | } | |||
| 2421 | } | |||
| 2422 | LLVM_DEBUG(dbgs() << "Aliasing okay for " << *(MemLoc.Ptr) << "\n")do { } while (false); | |||
| 2423 | return false; | |||
| 2424 | } | |||
| 2425 | ||||
| 2426 | bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, | |||
| 2427 | Loop *CurLoop, Instruction &I, | |||
| 2428 | SinkAndHoistLICMFlags &Flags) { | |||
| 2429 | // For hoisting, use the walker to determine safety | |||
| 2430 | if (!Flags.getIsSink()) { | |||
| 2431 | MemoryAccess *Source; | |||
| 2432 | // See declaration of SetLicmMssaOptCap for usage details. | |||
| 2433 | if (Flags.tooManyClobberingCalls()) | |||
| 2434 | Source = MU->getDefiningAccess(); | |||
| 2435 | else { | |||
| 2436 | Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(MU); | |||
| 2437 | Flags.incrementClobberingCalls(); | |||
| 2438 | } | |||
| 2439 | return !MSSA->isLiveOnEntryDef(Source) && | |||
| 2440 | CurLoop->contains(Source->getBlock()); | |||
| 2441 | } | |||
| 2442 | ||||
| 2443 | // For sinking, we'd need to check all Defs below this use. The getClobbering | |||
| 2444 | // call will look on the backedge of the loop, but will check aliasing with | |||
| 2445 | // the instructions on the previous iteration. | |||
| 2446 | // For example: | |||
| 2447 | // for (i ... ) | |||
| 2448 | // load a[i] ( Use (LoE) | |||
| 2449 | // store a[i] ( 1 = Def (2), with 2 = Phi for the loop. | |||
| 2450 | // i++; | |||
| 2451 | // The load sees no clobbering inside the loop, as the backedge alias check | |||
| 2452 | // does phi translation, and will check aliasing against store a[i-1]. | |||
| 2453 | // However sinking the load outside the loop, below the store is incorrect. | |||
| 2454 | ||||
| 2455 | // For now, only sink if there are no Defs in the loop, and the existing ones | |||
| 2456 | // precede the use and are in the same block. | |||
| 2457 | // FIXME: Increase precision: Safe to sink if Use post dominates the Def; | |||
| 2458 | // needs PostDominatorTreeAnalysis. | |||
| 2459 | // FIXME: More precise: no Defs that alias this Use. | |||
| 2460 | if (Flags.tooManyMemoryAccesses()) | |||
| 2461 | return true; | |||
| 2462 | for (auto *BB : CurLoop->getBlocks()) | |||
| 2463 | if (pointerInvalidatedByBlockWithMSSA(*BB, *MSSA, *MU)) | |||
| 2464 | return true; | |||
| 2465 | // When sinking, the source block may not be part of the loop so check it. | |||
| 2466 | if (!CurLoop->contains(&I)) | |||
| 2467 | return pointerInvalidatedByBlockWithMSSA(*I.getParent(), *MSSA, *MU); | |||
| 2468 | ||||
| 2469 | return false; | |||
| 2470 | } | |||
| 2471 | ||||
| 2472 | bool pointerInvalidatedByBlockWithMSSA(BasicBlock &BB, MemorySSA &MSSA, | |||
| 2473 | MemoryUse &MU) { | |||
| 2474 | if (const auto *Accesses = MSSA.getBlockDefs(&BB)) | |||
| 2475 | for (const auto &MA : *Accesses) | |||
| 2476 | if (const auto *MD = dyn_cast<MemoryDef>(&MA)) | |||
| 2477 | if (MU.getBlock() != MD->getBlock() || !MSSA.locallyDominates(MD, &MU)) | |||
| 2478 | return true; | |||
| 2479 | return false; | |||
| 2480 | } | |||
| 2481 | ||||
| 2482 | /// Little predicate that returns true if the specified basic block is in | |||
| 2483 | /// a subloop of the current one, not the current one itself. | |||
| 2484 | /// | |||
| 2485 | static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) { | |||
| 2486 | assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop")((void)0); | |||
| 2487 | return LI->getLoopFor(BB) != CurLoop; | |||
| 2488 | } |