| File: | lib/Transforms/Scalar/LICM.cpp |
| Warning: | line 1241, column 22 Called C++ object pointer is null |
Press '?' to see keyboard shortcuts
Keyboard shortcuts:
| 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 | // This pass uses alias analysis for two purposes: | |||
| 16 | // | |||
| 17 | // 1. Moving loop invariant loads and calls out of loops. If we can determine | |||
| 18 | // that a load or call inside of a loop never aliases anything stored to, | |||
| 19 | // we can hoist it or sink it like any other instruction. | |||
| 20 | // 2. Scalar Promotion of Memory - If there is a store instruction inside of | |||
| 21 | // the loop, we try to move the store to happen AFTER the loop instead of | |||
| 22 | // inside of the loop. This can only happen if a few conditions are true: | |||
| 23 | // A. The pointer stored through is loop invariant | |||
| 24 | // B. There are no stores or loads in the loop which _may_ alias the | |||
| 25 | // pointer. There are no calls in the loop which mod/ref the pointer. | |||
| 26 | // If these conditions are true, we can promote the loads and stores in the | |||
| 27 | // loop of the pointer to use a temporary alloca'd variable. We then use | |||
| 28 | // the SSAUpdater to construct the appropriate SSA form for the value. | |||
| 29 | // | |||
| 30 | //===----------------------------------------------------------------------===// | |||
| 31 | ||||
| 32 | #include "llvm/Transforms/Scalar/LICM.h" | |||
| 33 | #include "llvm/ADT/SetOperations.h" | |||
| 34 | #include "llvm/ADT/Statistic.h" | |||
| 35 | #include "llvm/Analysis/AliasAnalysis.h" | |||
| 36 | #include "llvm/Analysis/AliasSetTracker.h" | |||
| 37 | #include "llvm/Analysis/BasicAliasAnalysis.h" | |||
| 38 | #include "llvm/Analysis/CaptureTracking.h" | |||
| 39 | #include "llvm/Analysis/ConstantFolding.h" | |||
| 40 | #include "llvm/Analysis/GlobalsModRef.h" | |||
| 41 | #include "llvm/Analysis/GuardUtils.h" | |||
| 42 | #include "llvm/Analysis/Loads.h" | |||
| 43 | #include "llvm/Analysis/LoopInfo.h" | |||
| 44 | #include "llvm/Analysis/LoopIterator.h" | |||
| 45 | #include "llvm/Analysis/LoopPass.h" | |||
| 46 | #include "llvm/Analysis/MemoryBuiltins.h" | |||
| 47 | #include "llvm/Analysis/MemorySSA.h" | |||
| 48 | #include "llvm/Analysis/MemorySSAUpdater.h" | |||
| 49 | #include "llvm/Analysis/OptimizationRemarkEmitter.h" | |||
| 50 | #include "llvm/Analysis/ScalarEvolution.h" | |||
| 51 | #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h" | |||
| 52 | #include "llvm/Analysis/TargetLibraryInfo.h" | |||
| 53 | #include "llvm/Analysis/ValueTracking.h" | |||
| 54 | #include "llvm/IR/CFG.h" | |||
| 55 | #include "llvm/IR/Constants.h" | |||
| 56 | #include "llvm/IR/DataLayout.h" | |||
| 57 | #include "llvm/IR/DebugInfoMetadata.h" | |||
| 58 | #include "llvm/IR/DerivedTypes.h" | |||
| 59 | #include "llvm/IR/Dominators.h" | |||
| 60 | #include "llvm/IR/Instructions.h" | |||
| 61 | #include "llvm/IR/IntrinsicInst.h" | |||
| 62 | #include "llvm/IR/LLVMContext.h" | |||
| 63 | #include "llvm/IR/Metadata.h" | |||
| 64 | #include "llvm/IR/PatternMatch.h" | |||
| 65 | #include "llvm/IR/PredIteratorCache.h" | |||
| 66 | #include "llvm/Support/CommandLine.h" | |||
| 67 | #include "llvm/Support/Debug.h" | |||
| 68 | #include "llvm/Support/raw_ostream.h" | |||
| 69 | #include "llvm/Transforms/Scalar.h" | |||
| 70 | #include "llvm/Transforms/Scalar/LoopPassManager.h" | |||
| 71 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | |||
| 72 | #include "llvm/Transforms/Utils/Local.h" | |||
| 73 | #include "llvm/Transforms/Utils/LoopUtils.h" | |||
| 74 | #include "llvm/Transforms/Utils/SSAUpdater.h" | |||
| 75 | #include <algorithm> | |||
| 76 | #include <utility> | |||
| 77 | using namespace llvm; | |||
| 78 | ||||
| 79 | #define DEBUG_TYPE"licm" "licm" | |||
| 80 | ||||
| 81 | STATISTIC(NumCreatedBlocks, "Number of blocks created")static llvm::Statistic NumCreatedBlocks = {"licm", "NumCreatedBlocks" , "Number of blocks created", {0}, {false}}; | |||
| 82 | STATISTIC(NumClonedBranches, "Number of branches cloned")static llvm::Statistic NumClonedBranches = {"licm", "NumClonedBranches" , "Number of branches cloned", {0}, {false}}; | |||
| 83 | STATISTIC(NumSunk, "Number of instructions sunk out of loop")static llvm::Statistic NumSunk = {"licm", "NumSunk", "Number of instructions sunk out of loop" , {0}, {false}}; | |||
| 84 | STATISTIC(NumHoisted, "Number of instructions hoisted out of loop")static llvm::Statistic NumHoisted = {"licm", "NumHoisted", "Number of instructions hoisted out of loop" , {0}, {false}}; | |||
| 85 | STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk")static llvm::Statistic NumMovedLoads = {"licm", "NumMovedLoads" , "Number of load insts hoisted or sunk", {0}, {false}}; | |||
| 86 | STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk")static llvm::Statistic NumMovedCalls = {"licm", "NumMovedCalls" , "Number of call insts hoisted or sunk", {0}, {false}}; | |||
| 87 | STATISTIC(NumPromoted, "Number of memory locations promoted to registers")static llvm::Statistic NumPromoted = {"licm", "NumPromoted", "Number of memory locations promoted to registers" , {0}, {false}}; | |||
| 88 | ||||
| 89 | /// Memory promotion is enabled by default. | |||
| 90 | static cl::opt<bool> | |||
| 91 | DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false), | |||
| 92 | cl::desc("Disable memory promotion in LICM pass")); | |||
| 93 | ||||
| 94 | static cl::opt<bool> ControlFlowHoisting( | |||
| 95 | "licm-control-flow-hoisting", cl::Hidden, cl::init(false), | |||
| 96 | cl::desc("Enable control flow (and PHI) hoisting in LICM")); | |||
| 97 | ||||
| 98 | static cl::opt<uint32_t> MaxNumUsesTraversed( | |||
| 99 | "licm-max-num-uses-traversed", cl::Hidden, cl::init(8), | |||
| 100 | cl::desc("Max num uses visited for identifying load " | |||
| 101 | "invariance in loop using invariant start (default = 8)")); | |||
| 102 | ||||
| 103 | // Default value of zero implies we use the regular alias set tracker mechanism | |||
| 104 | // instead of the cross product using AA to identify aliasing of the memory | |||
| 105 | // location we are interested in. | |||
| 106 | static cl::opt<int> | |||
| 107 | LICMN2Theshold("licm-n2-threshold", cl::Hidden, cl::init(0), | |||
| 108 | cl::desc("How many instruction to cross product using AA")); | |||
| 109 | ||||
| 110 | // Experimental option to allow imprecision in LICM in pathological cases, in | |||
| 111 | // exchange for faster compile. This is to be removed if MemorySSA starts to | |||
| 112 | // address the same issue. This flag applies only when LICM uses MemorySSA | |||
| 113 | // instead on AliasSetTracker. LICM calls MemorySSAWalker's | |||
| 114 | // getClobberingMemoryAccess, up to the value of the Cap, getting perfect | |||
| 115 | // accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess, | |||
| 116 | // which may not be precise, since optimizeUses is capped. The result is | |||
| 117 | // correct, but we may not get as "far up" as possible to get which access is | |||
| 118 | // clobbering the one queried. | |||
| 119 | cl::opt<unsigned> llvm::SetLicmMssaOptCap( | |||
| 120 | "licm-mssa-optimization-cap", cl::init(100), cl::Hidden, | |||
| 121 | cl::desc("Enable imprecision in LICM in pathological cases, in exchange " | |||
| 122 | "for faster compile. Caps the MemorySSA clobbering calls.")); | |||
| 123 | ||||
| 124 | // Experimentally, memory promotion carries less importance than sinking and | |||
| 125 | // hoisting. Limit when we do promotion when using MemorySSA, in order to save | |||
| 126 | // compile time. | |||
| 127 | cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap( | |||
| 128 | "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden, | |||
| 129 | cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no " | |||
| 130 | "effect. When MSSA in LICM is enabled, then this is the maximum " | |||
| 131 | "number of accesses allowed to be present in a loop in order to " | |||
| 132 | "enable memory promotion.")); | |||
| 133 | ||||
| 134 | static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI); | |||
| 135 | static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 136 | const LoopSafetyInfo *SafetyInfo, | |||
| 137 | TargetTransformInfo *TTI, bool &FreeInLoop); | |||
| 138 | static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, | |||
| 139 | BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, | |||
| 140 | MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE); | |||
| 141 | static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, | |||
| 142 | const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, | |||
| 143 | MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE); | |||
| 144 | static bool isSafeToExecuteUnconditionally(Instruction &Inst, | |||
| 145 | const DominatorTree *DT, | |||
| 146 | const Loop *CurLoop, | |||
| 147 | const LoopSafetyInfo *SafetyInfo, | |||
| 148 | OptimizationRemarkEmitter *ORE, | |||
| 149 | const Instruction *CtxI = nullptr); | |||
| 150 | static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, | |||
| 151 | AliasSetTracker *CurAST, Loop *CurLoop, | |||
| 152 | AliasAnalysis *AA); | |||
| 153 | static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, | |||
| 154 | Loop *CurLoop, | |||
| 155 | SinkAndHoistLICMFlags &Flags); | |||
| 156 | static Instruction *CloneInstructionInExitBlock( | |||
| 157 | Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, | |||
| 158 | const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU); | |||
| 159 | ||||
| 160 | static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, | |||
| 161 | AliasSetTracker *AST, MemorySSAUpdater *MSSAU); | |||
| 162 | ||||
| 163 | static void moveInstructionBefore(Instruction &I, Instruction &Dest, | |||
| 164 | ICFLoopSafetyInfo &SafetyInfo, | |||
| 165 | MemorySSAUpdater *MSSAU); | |||
| 166 | ||||
| 167 | namespace { | |||
| 168 | struct LoopInvariantCodeMotion { | |||
| 169 | using ASTrackerMapTy = DenseMap<Loop *, std::unique_ptr<AliasSetTracker>>; | |||
| 170 | bool runOnLoop(Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT, | |||
| 171 | TargetLibraryInfo *TLI, TargetTransformInfo *TTI, | |||
| 172 | ScalarEvolution *SE, MemorySSA *MSSA, | |||
| 173 | OptimizationRemarkEmitter *ORE, bool DeleteAST); | |||
| 174 | ||||
| 175 | ASTrackerMapTy &getLoopToAliasSetMap() { return LoopToAliasSetMap; } | |||
| 176 | LoopInvariantCodeMotion(unsigned LicmMssaOptCap, | |||
| 177 | unsigned LicmMssaNoAccForPromotionCap) | |||
| 178 | : LicmMssaOptCap(LicmMssaOptCap), | |||
| 179 | LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap) {} | |||
| 180 | ||||
| 181 | private: | |||
| 182 | ASTrackerMapTy LoopToAliasSetMap; | |||
| 183 | unsigned LicmMssaOptCap; | |||
| 184 | unsigned LicmMssaNoAccForPromotionCap; | |||
| 185 | ||||
| 186 | std::unique_ptr<AliasSetTracker> | |||
| 187 | collectAliasInfoForLoop(Loop *L, LoopInfo *LI, AliasAnalysis *AA); | |||
| 188 | std::unique_ptr<AliasSetTracker> | |||
| 189 | collectAliasInfoForLoopWithMSSA(Loop *L, AliasAnalysis *AA, | |||
| 190 | MemorySSAUpdater *MSSAU); | |||
| 191 | }; | |||
| 192 | ||||
| 193 | struct LegacyLICMPass : public LoopPass { | |||
| 194 | static char ID; // Pass identification, replacement for typeid | |||
| 195 | LegacyLICMPass( | |||
| 196 | unsigned LicmMssaOptCap = SetLicmMssaOptCap, | |||
| 197 | unsigned LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap) | |||
| 198 | : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) { | |||
| 199 | initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry()); | |||
| 200 | } | |||
| 201 | ||||
| 202 | bool runOnLoop(Loop *L, LPPassManager &LPM) override { | |||
| 203 | if (skipLoop(L)) { | |||
| 204 | // If we have run LICM on a previous loop but now we are skipping | |||
| 205 | // (because we've hit the opt-bisect limit), we need to clear the | |||
| 206 | // loop alias information. | |||
| 207 | LICM.getLoopToAliasSetMap().clear(); | |||
| 208 | return false; | |||
| 209 | } | |||
| 210 | ||||
| 211 | auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); | |||
| 212 | MemorySSA *MSSA = EnableMSSALoopDependency | |||
| 213 | ? (&getAnalysis<MemorySSAWrapperPass>().getMSSA()) | |||
| 214 | : nullptr; | |||
| 215 | // For the old PM, we can't use OptimizationRemarkEmitter as an analysis | |||
| 216 | // pass. Function analyses need to be preserved across loop transformations | |||
| 217 | // but ORE cannot be preserved (see comment before the pass definition). | |||
| 218 | OptimizationRemarkEmitter ORE(L->getHeader()->getParent()); | |||
| 219 | return LICM.runOnLoop(L, | |||
| 220 | &getAnalysis<AAResultsWrapperPass>().getAAResults(), | |||
| 221 | &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(), | |||
| 222 | &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), | |||
| 223 | &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(), | |||
| 224 | &getAnalysis<TargetTransformInfoWrapperPass>().getTTI( | |||
| 225 | *L->getHeader()->getParent()), | |||
| 226 | SE ? &SE->getSE() : nullptr, MSSA, &ORE, false); | |||
| 227 | } | |||
| 228 | ||||
| 229 | /// This transformation requires natural loop information & requires that | |||
| 230 | /// loop preheaders be inserted into the CFG... | |||
| 231 | /// | |||
| 232 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||
| 233 | AU.addPreserved<DominatorTreeWrapperPass>(); | |||
| 234 | AU.addPreserved<LoopInfoWrapperPass>(); | |||
| 235 | AU.addRequired<TargetLibraryInfoWrapperPass>(); | |||
| 236 | if (EnableMSSALoopDependency) { | |||
| 237 | AU.addRequired<MemorySSAWrapperPass>(); | |||
| 238 | AU.addPreserved<MemorySSAWrapperPass>(); | |||
| 239 | } | |||
| 240 | AU.addRequired<TargetTransformInfoWrapperPass>(); | |||
| 241 | getLoopAnalysisUsage(AU); | |||
| 242 | } | |||
| 243 | ||||
| 244 | using llvm::Pass::doFinalization; | |||
| 245 | ||||
| 246 | bool doFinalization() override { | |||
| 247 | auto &AliasSetMap = LICM.getLoopToAliasSetMap(); | |||
| 248 | // All loops in the AliasSetMap should be cleaned up already. The only case | |||
| 249 | // where we fail to do so is if an outer loop gets deleted before LICM | |||
| 250 | // visits it. | |||
| 251 | assert(all_of(AliasSetMap,((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy ::value_type &KV) { return !KV.first->getParentLoop(); }) && "Didn't free loop alias sets") ? static_cast< void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 255, __PRETTY_FUNCTION__)) | |||
| 252 | [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) {((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy ::value_type &KV) { return !KV.first->getParentLoop(); }) && "Didn't free loop alias sets") ? static_cast< void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 255, __PRETTY_FUNCTION__)) | |||
| 253 | return !KV.first->getParentLoop();((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy ::value_type &KV) { return !KV.first->getParentLoop(); }) && "Didn't free loop alias sets") ? static_cast< void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 255, __PRETTY_FUNCTION__)) | |||
| 254 | }) &&((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy ::value_type &KV) { return !KV.first->getParentLoop(); }) && "Didn't free loop alias sets") ? static_cast< void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 255, __PRETTY_FUNCTION__)) | |||
| 255 | "Didn't free loop alias sets")((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy ::value_type &KV) { return !KV.first->getParentLoop(); }) && "Didn't free loop alias sets") ? static_cast< void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 255, __PRETTY_FUNCTION__)); | |||
| 256 | AliasSetMap.clear(); | |||
| 257 | return false; | |||
| 258 | } | |||
| 259 | ||||
| 260 | private: | |||
| 261 | LoopInvariantCodeMotion LICM; | |||
| 262 | ||||
| 263 | /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. | |||
| 264 | void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, | |||
| 265 | Loop *L) override; | |||
| 266 | ||||
| 267 | /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias | |||
| 268 | /// set. | |||
| 269 | void deleteAnalysisValue(Value *V, Loop *L) override; | |||
| 270 | ||||
| 271 | /// Simple Analysis hook. Delete loop L from alias set map. | |||
| 272 | void deleteAnalysisLoop(Loop *L) override; | |||
| 273 | }; | |||
| 274 | } // namespace | |||
| 275 | ||||
| 276 | PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM, | |||
| 277 | LoopStandardAnalysisResults &AR, LPMUpdater &) { | |||
| 278 | const auto &FAM = | |||
| 279 | AM.getResult<FunctionAnalysisManagerLoopProxy>(L, AR).getManager(); | |||
| 280 | Function *F = L.getHeader()->getParent(); | |||
| 281 | ||||
| 282 | auto *ORE = FAM.getCachedResult<OptimizationRemarkEmitterAnalysis>(*F); | |||
| 283 | // FIXME: This should probably be optional rather than required. | |||
| 284 | if (!ORE) | |||
| 285 | report_fatal_error("LICM: OptimizationRemarkEmitterAnalysis not " | |||
| 286 | "cached at a higher level"); | |||
| 287 | ||||
| 288 | LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); | |||
| 289 | if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.TLI, &AR.TTI, &AR.SE, | |||
| 290 | AR.MSSA, ORE, true)) | |||
| 291 | return PreservedAnalyses::all(); | |||
| 292 | ||||
| 293 | auto PA = getLoopPassPreservedAnalyses(); | |||
| 294 | ||||
| 295 | PA.preserve<DominatorTreeAnalysis>(); | |||
| 296 | PA.preserve<LoopAnalysis>(); | |||
| 297 | ||||
| 298 | return PA; | |||
| 299 | } | |||
| 300 | ||||
| 301 | char LegacyLICMPass::ID = 0; | |||
| 302 | INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion",static void *initializeLegacyLICMPassPassOnce(PassRegistry & Registry) { | |||
| 303 | false, false)static void *initializeLegacyLICMPassPassOnce(PassRegistry & Registry) { | |||
| 304 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | |||
| 305 | INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry); | |||
| 306 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | |||
| 307 | INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry); | |||
| 308 | 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)); } | |||
| 309 | 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)); } | |||
| 310 | ||||
| 311 | Pass *llvm::createLICMPass() { return new LegacyLICMPass(); } | |||
| 312 | Pass *llvm::createLICMPass(unsigned LicmMssaOptCap, | |||
| 313 | unsigned LicmMssaNoAccForPromotionCap) { | |||
| 314 | return new LegacyLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); | |||
| 315 | } | |||
| 316 | ||||
| 317 | /// Hoist expressions out of the specified loop. Note, alias info for inner | |||
| 318 | /// loop is not preserved so it is not a good idea to run LICM multiple | |||
| 319 | /// times on one loop. | |||
| 320 | /// We should delete AST for inner loops in the new pass manager to avoid | |||
| 321 | /// memory leak. | |||
| 322 | /// | |||
| 323 | bool LoopInvariantCodeMotion::runOnLoop( | |||
| 324 | Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT, | |||
| 325 | TargetLibraryInfo *TLI, TargetTransformInfo *TTI, ScalarEvolution *SE, | |||
| 326 | MemorySSA *MSSA, OptimizationRemarkEmitter *ORE, bool DeleteAST) { | |||
| 327 | bool Changed = false; | |||
| 328 | ||||
| 329 | assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.")((L->isLCSSAForm(*DT) && "Loop is not in LCSSA form." ) ? static_cast<void> (0) : __assert_fail ("L->isLCSSAForm(*DT) && \"Loop is not in LCSSA form.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 329, __PRETTY_FUNCTION__)); | |||
| 330 | ||||
| 331 | std::unique_ptr<AliasSetTracker> CurAST; | |||
| 332 | std::unique_ptr<MemorySSAUpdater> MSSAU; | |||
| 333 | bool NoOfMemAccTooLarge = false; | |||
| 334 | unsigned LicmMssaOptCounter = 0; | |||
| 335 | ||||
| 336 | if (!MSSA) { | |||
| 337 | LLVM_DEBUG(dbgs() << "LICM: Using Alias Set Tracker.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM: Using Alias Set Tracker.\n" ; } } while (false); | |||
| 338 | CurAST = collectAliasInfoForLoop(L, LI, AA); | |||
| 339 | } else { | |||
| 340 | LLVM_DEBUG(dbgs() << "LICM: Using MemorySSA.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM: Using MemorySSA.\n"; } } while (false); | |||
| 341 | MSSAU = make_unique<MemorySSAUpdater>(MSSA); | |||
| 342 | ||||
| 343 | unsigned AccessCapCount = 0; | |||
| 344 | for (auto *BB : L->getBlocks()) { | |||
| 345 | if (auto *Accesses = MSSA->getBlockAccesses(BB)) { | |||
| 346 | for (const auto &MA : *Accesses) { | |||
| 347 | (void)MA; | |||
| 348 | AccessCapCount++; | |||
| 349 | if (AccessCapCount > LicmMssaNoAccForPromotionCap) { | |||
| 350 | NoOfMemAccTooLarge = true; | |||
| 351 | break; | |||
| 352 | } | |||
| 353 | } | |||
| 354 | } | |||
| 355 | if (NoOfMemAccTooLarge) | |||
| 356 | break; | |||
| 357 | } | |||
| 358 | } | |||
| 359 | ||||
| 360 | // Get the preheader block to move instructions into... | |||
| 361 | BasicBlock *Preheader = L->getLoopPreheader(); | |||
| 362 | ||||
| 363 | // Compute loop safety information. | |||
| 364 | ICFLoopSafetyInfo SafetyInfo(DT); | |||
| 365 | SafetyInfo.computeLoopSafetyInfo(L); | |||
| 366 | ||||
| 367 | // We want to visit all of the instructions in this loop... that are not parts | |||
| 368 | // of our subloops (they have already had their invariants hoisted out of | |||
| 369 | // their loop, into this loop, so there is no need to process the BODIES of | |||
| 370 | // the subloops). | |||
| 371 | // | |||
| 372 | // Traverse the body of the loop in depth first order on the dominator tree so | |||
| 373 | // that we are guaranteed to see definitions before we see uses. This allows | |||
| 374 | // us to sink instructions in one pass, without iteration. After sinking | |||
| 375 | // instructions, we perform another pass to hoist them out of the loop. | |||
| 376 | SinkAndHoistLICMFlags Flags = {NoOfMemAccTooLarge, LicmMssaOptCounter, | |||
| 377 | LicmMssaOptCap, LicmMssaNoAccForPromotionCap}; | |||
| 378 | if (L->hasDedicatedExits()) | |||
| 379 | Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, TTI, L, | |||
| 380 | CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE); | |||
| 381 | if (Preheader) | |||
| 382 | Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L, | |||
| 383 | CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE); | |||
| 384 | ||||
| 385 | // Now that all loop invariants have been removed from the loop, promote any | |||
| 386 | // memory references to scalars that we can. | |||
| 387 | // Don't sink stores from loops without dedicated block exits. Exits | |||
| 388 | // containing indirect branches are not transformed by loop simplify, | |||
| 389 | // make sure we catch that. An additional load may be generated in the | |||
| 390 | // preheader for SSA updater, so also avoid sinking when no preheader | |||
| 391 | // is available. | |||
| 392 | if (!DisablePromotion && Preheader && L->hasDedicatedExits() && | |||
| 393 | !NoOfMemAccTooLarge) { | |||
| 394 | // Figure out the loop exits and their insertion points | |||
| 395 | SmallVector<BasicBlock *, 8> ExitBlocks; | |||
| 396 | L->getUniqueExitBlocks(ExitBlocks); | |||
| 397 | ||||
| 398 | // We can't insert into a catchswitch. | |||
| 399 | bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) { | |||
| 400 | return isa<CatchSwitchInst>(Exit->getTerminator()); | |||
| 401 | }); | |||
| 402 | ||||
| 403 | if (!HasCatchSwitch) { | |||
| 404 | SmallVector<Instruction *, 8> InsertPts; | |||
| 405 | SmallVector<MemoryAccess *, 8> MSSAInsertPts; | |||
| 406 | InsertPts.reserve(ExitBlocks.size()); | |||
| 407 | if (MSSAU) | |||
| 408 | MSSAInsertPts.reserve(ExitBlocks.size()); | |||
| 409 | for (BasicBlock *ExitBlock : ExitBlocks) { | |||
| 410 | InsertPts.push_back(&*ExitBlock->getFirstInsertionPt()); | |||
| 411 | if (MSSAU) | |||
| 412 | MSSAInsertPts.push_back(nullptr); | |||
| 413 | } | |||
| 414 | ||||
| 415 | PredIteratorCache PIC; | |||
| 416 | ||||
| 417 | bool Promoted = false; | |||
| 418 | ||||
| 419 | // Build an AST using MSSA. | |||
| 420 | if (!CurAST.get()) | |||
| 421 | CurAST = collectAliasInfoForLoopWithMSSA(L, AA, MSSAU.get()); | |||
| 422 | ||||
| 423 | // Loop over all of the alias sets in the tracker object. | |||
| 424 | for (AliasSet &AS : *CurAST) { | |||
| 425 | // We can promote this alias set if it has a store, if it is a "Must" | |||
| 426 | // alias set, if the pointer is loop invariant, and if we are not | |||
| 427 | // eliminating any volatile loads or stores. | |||
| 428 | if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || | |||
| 429 | !L->isLoopInvariant(AS.begin()->getValue())) | |||
| 430 | continue; | |||
| 431 | ||||
| 432 | assert(((!AS.empty() && "Must alias set should have at least one pointer element in it!" ) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 434, __PRETTY_FUNCTION__)) | |||
| 433 | !AS.empty() &&((!AS.empty() && "Must alias set should have at least one pointer element in it!" ) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 434, __PRETTY_FUNCTION__)) | |||
| 434 | "Must alias set should have at least one pointer element in it!")((!AS.empty() && "Must alias set should have at least one pointer element in it!" ) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 434, __PRETTY_FUNCTION__)); | |||
| 435 | ||||
| 436 | SmallSetVector<Value *, 8> PointerMustAliases; | |||
| 437 | for (const auto &ASI : AS) | |||
| 438 | PointerMustAliases.insert(ASI.getValue()); | |||
| 439 | ||||
| 440 | Promoted |= promoteLoopAccessesToScalars( | |||
| 441 | PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC, LI, | |||
| 442 | DT, TLI, L, CurAST.get(), MSSAU.get(), &SafetyInfo, ORE); | |||
| 443 | } | |||
| 444 | ||||
| 445 | // Once we have promoted values across the loop body we have to | |||
| 446 | // recursively reform LCSSA as any nested loop may now have values defined | |||
| 447 | // within the loop used in the outer loop. | |||
| 448 | // FIXME: This is really heavy handed. It would be a bit better to use an | |||
| 449 | // SSAUpdater strategy during promotion that was LCSSA aware and reformed | |||
| 450 | // it as it went. | |||
| 451 | if (Promoted) | |||
| 452 | formLCSSARecursively(*L, *DT, LI, SE); | |||
| 453 | ||||
| 454 | Changed |= Promoted; | |||
| 455 | } | |||
| 456 | } | |||
| 457 | ||||
| 458 | // Check that neither this loop nor its parent have had LCSSA broken. LICM is | |||
| 459 | // specifically moving instructions across the loop boundary and so it is | |||
| 460 | // especially in need of sanity checking here. | |||
| 461 | assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!")((L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!" ) ? static_cast<void> (0) : __assert_fail ("L->isLCSSAForm(*DT) && \"Loop not left in LCSSA form after LICM!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 461, __PRETTY_FUNCTION__)); | |||
| 462 | assert((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) &&(((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm (*DT)) && "Parent loop not left in LCSSA form after LICM!" ) ? static_cast<void> (0) : __assert_fail ("(!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) && \"Parent loop not left in LCSSA form after LICM!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 463, __PRETTY_FUNCTION__)) | |||
| 463 | "Parent loop not left in LCSSA form after LICM!")(((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm (*DT)) && "Parent loop not left in LCSSA form after LICM!" ) ? static_cast<void> (0) : __assert_fail ("(!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) && \"Parent loop not left in LCSSA form after LICM!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 463, __PRETTY_FUNCTION__)); | |||
| 464 | ||||
| 465 | // If this loop is nested inside of another one, save the alias information | |||
| 466 | // for when we process the outer loop. | |||
| 467 | if (!MSSAU.get() && CurAST.get() && L->getParentLoop() && !DeleteAST) | |||
| 468 | LoopToAliasSetMap[L] = std::move(CurAST); | |||
| 469 | ||||
| 470 | if (MSSAU.get() && VerifyMemorySSA) | |||
| 471 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 472 | ||||
| 473 | if (Changed && SE) | |||
| 474 | SE->forgetLoopDispositions(L); | |||
| 475 | return Changed; | |||
| 476 | } | |||
| 477 | ||||
| 478 | /// Walk the specified region of the CFG (defined by all blocks dominated by | |||
| 479 | /// the specified block, and that are in the current loop) in reverse depth | |||
| 480 | /// first order w.r.t the DominatorTree. This allows us to visit uses before | |||
| 481 | /// definitions, allowing us to sink a loop body in one pass without iteration. | |||
| 482 | /// | |||
| 483 | bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, | |||
| 484 | DominatorTree *DT, TargetLibraryInfo *TLI, | |||
| 485 | TargetTransformInfo *TTI, Loop *CurLoop, | |||
| 486 | AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, | |||
| 487 | ICFLoopSafetyInfo *SafetyInfo, | |||
| 488 | SinkAndHoistLICMFlags &Flags, | |||
| 489 | OptimizationRemarkEmitter *ORE) { | |||
| 490 | ||||
| 491 | // Verify inputs. | |||
| 492 | assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to sinkRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 494, __PRETTY_FUNCTION__)) | |||
| 493 | CurLoop != nullptr && SafetyInfo != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to sinkRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 494, __PRETTY_FUNCTION__)) | |||
| 494 | "Unexpected input to sinkRegion.")((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to sinkRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 494, __PRETTY_FUNCTION__)); | |||
| 495 | assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized." ) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 496, __PRETTY_FUNCTION__)) | |||
| 496 | "Either AliasSetTracker or MemorySSA should be initialized.")((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized." ) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 496, __PRETTY_FUNCTION__)); | |||
| 497 | ||||
| 498 | // We want to visit children before parents. We will enque all the parents | |||
| 499 | // before their children in the worklist and process the worklist in reverse | |||
| 500 | // order. | |||
| 501 | SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop); | |||
| 502 | ||||
| 503 | bool Changed = false; | |||
| 504 | for (DomTreeNode *DTN : reverse(Worklist)) { | |||
| 505 | BasicBlock *BB = DTN->getBlock(); | |||
| 506 | // Only need to process the contents of this block if it is not part of a | |||
| 507 | // subloop (which would already have been processed). | |||
| 508 | if (inSubLoop(BB, CurLoop, LI)) | |||
| 509 | continue; | |||
| 510 | ||||
| 511 | for (BasicBlock::iterator II = BB->end(); II != BB->begin();) { | |||
| 512 | Instruction &I = *--II; | |||
| 513 | ||||
| 514 | // If the instruction is dead, we would try to sink it because it isn't | |||
| 515 | // used in the loop, instead, just delete it. | |||
| 516 | if (isInstructionTriviallyDead(&I, TLI)) { | |||
| 517 | LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM deleting dead inst: " << I << '\n'; } } while (false); | |||
| 518 | salvageDebugInfo(I); | |||
| 519 | ++II; | |||
| 520 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 521 | Changed = true; | |||
| 522 | continue; | |||
| 523 | } | |||
| 524 | ||||
| 525 | // Check to see if we can sink this instruction to the exit blocks | |||
| 526 | // of the loop. We can do this if the all users of the instruction are | |||
| 527 | // outside of the loop. In this case, it doesn't even matter if the | |||
| 528 | // operands of the instruction are loop invariant. | |||
| 529 | // | |||
| 530 | bool FreeInLoop = false; | |||
| 531 | if (isNotUsedOrFreeInLoop(I, CurLoop, SafetyInfo, TTI, FreeInLoop) && | |||
| 532 | canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, | |||
| 533 | ORE) && | |||
| 534 | !I.mayHaveSideEffects()) { | |||
| 535 | if (sink(I, LI, DT, CurLoop, SafetyInfo, MSSAU, ORE)) { | |||
| 536 | if (!FreeInLoop) { | |||
| 537 | ++II; | |||
| 538 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 539 | } | |||
| 540 | Changed = true; | |||
| 541 | } | |||
| 542 | } | |||
| 543 | } | |||
| 544 | } | |||
| 545 | if (MSSAU && VerifyMemorySSA) | |||
| 546 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 547 | return Changed; | |||
| 548 | } | |||
| 549 | ||||
| 550 | namespace { | |||
| 551 | // This is a helper class for hoistRegion to make it able to hoist control flow | |||
| 552 | // in order to be able to hoist phis. The way this works is that we initially | |||
| 553 | // start hoisting to the loop preheader, and when we see a loop invariant branch | |||
| 554 | // we make note of this. When we then come to hoist an instruction that's | |||
| 555 | // conditional on such a branch we duplicate the branch and the relevant control | |||
| 556 | // flow, then hoist the instruction into the block corresponding to its original | |||
| 557 | // block in the duplicated control flow. | |||
| 558 | class ControlFlowHoister { | |||
| 559 | private: | |||
| 560 | // Information about the loop we are hoisting from | |||
| 561 | LoopInfo *LI; | |||
| 562 | DominatorTree *DT; | |||
| 563 | Loop *CurLoop; | |||
| 564 | MemorySSAUpdater *MSSAU; | |||
| 565 | ||||
| 566 | // A map of blocks in the loop to the block their instructions will be hoisted | |||
| 567 | // to. | |||
| 568 | DenseMap<BasicBlock *, BasicBlock *> HoistDestinationMap; | |||
| 569 | ||||
| 570 | // The branches that we can hoist, mapped to the block that marks a | |||
| 571 | // convergence point of their control flow. | |||
| 572 | DenseMap<BranchInst *, BasicBlock *> HoistableBranches; | |||
| 573 | ||||
| 574 | public: | |||
| 575 | ControlFlowHoister(LoopInfo *LI, DominatorTree *DT, Loop *CurLoop, | |||
| 576 | MemorySSAUpdater *MSSAU) | |||
| 577 | : LI(LI), DT(DT), CurLoop(CurLoop), MSSAU(MSSAU) {} | |||
| 578 | ||||
| 579 | void registerPossiblyHoistableBranch(BranchInst *BI) { | |||
| 580 | // We can only hoist conditional branches with loop invariant operands. | |||
| 581 | if (!ControlFlowHoisting || !BI->isConditional() || | |||
| 582 | !CurLoop->hasLoopInvariantOperands(BI)) | |||
| 583 | return; | |||
| 584 | ||||
| 585 | // The branch destinations need to be in the loop, and we don't gain | |||
| 586 | // anything by duplicating conditional branches with duplicate successors, | |||
| 587 | // as it's essentially the same as an unconditional branch. | |||
| 588 | BasicBlock *TrueDest = BI->getSuccessor(0); | |||
| 589 | BasicBlock *FalseDest = BI->getSuccessor(1); | |||
| 590 | if (!CurLoop->contains(TrueDest) || !CurLoop->contains(FalseDest) || | |||
| 591 | TrueDest == FalseDest) | |||
| 592 | return; | |||
| 593 | ||||
| 594 | // We can hoist BI if one branch destination is the successor of the other, | |||
| 595 | // or both have common successor which we check by seeing if the | |||
| 596 | // intersection of their successors is non-empty. | |||
| 597 | // TODO: This could be expanded to allowing branches where both ends | |||
| 598 | // eventually converge to a single block. | |||
| 599 | SmallPtrSet<BasicBlock *, 4> TrueDestSucc, FalseDestSucc; | |||
| 600 | TrueDestSucc.insert(succ_begin(TrueDest), succ_end(TrueDest)); | |||
| 601 | FalseDestSucc.insert(succ_begin(FalseDest), succ_end(FalseDest)); | |||
| 602 | BasicBlock *CommonSucc = nullptr; | |||
| 603 | if (TrueDestSucc.count(FalseDest)) { | |||
| 604 | CommonSucc = FalseDest; | |||
| 605 | } else if (FalseDestSucc.count(TrueDest)) { | |||
| 606 | CommonSucc = TrueDest; | |||
| 607 | } else { | |||
| 608 | set_intersect(TrueDestSucc, FalseDestSucc); | |||
| 609 | // If there's one common successor use that. | |||
| 610 | if (TrueDestSucc.size() == 1) | |||
| 611 | CommonSucc = *TrueDestSucc.begin(); | |||
| 612 | // If there's more than one pick whichever appears first in the block list | |||
| 613 | // (we can't use the value returned by TrueDestSucc.begin() as it's | |||
| 614 | // unpredicatable which element gets returned). | |||
| 615 | else if (!TrueDestSucc.empty()) { | |||
| 616 | Function *F = TrueDest->getParent(); | |||
| 617 | auto IsSucc = [&](BasicBlock &BB) { return TrueDestSucc.count(&BB); }; | |||
| 618 | auto It = std::find_if(F->begin(), F->end(), IsSucc); | |||
| 619 | assert(It != F->end() && "Could not find successor in function")((It != F->end() && "Could not find successor in function" ) ? static_cast<void> (0) : __assert_fail ("It != F->end() && \"Could not find successor in function\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 619, __PRETTY_FUNCTION__)); | |||
| 620 | CommonSucc = &*It; | |||
| 621 | } | |||
| 622 | } | |||
| 623 | // The common successor has to be dominated by the branch, as otherwise | |||
| 624 | // there will be some other path to the successor that will not be | |||
| 625 | // controlled by this branch so any phi we hoist would be controlled by the | |||
| 626 | // wrong condition. This also takes care of avoiding hoisting of loop back | |||
| 627 | // edges. | |||
| 628 | // TODO: In some cases this could be relaxed if the successor is dominated | |||
| 629 | // by another block that's been hoisted and we can guarantee that the | |||
| 630 | // control flow has been replicated exactly. | |||
| 631 | if (CommonSucc && DT->dominates(BI, CommonSucc)) | |||
| 632 | HoistableBranches[BI] = CommonSucc; | |||
| 633 | } | |||
| 634 | ||||
| 635 | bool canHoistPHI(PHINode *PN) { | |||
| 636 | // The phi must have loop invariant operands. | |||
| 637 | if (!ControlFlowHoisting || !CurLoop->hasLoopInvariantOperands(PN)) | |||
| 638 | return false; | |||
| 639 | // We can hoist phis if the block they are in is the target of hoistable | |||
| 640 | // branches which cover all of the predecessors of the block. | |||
| 641 | SmallPtrSet<BasicBlock *, 8> PredecessorBlocks; | |||
| 642 | BasicBlock *BB = PN->getParent(); | |||
| 643 | for (BasicBlock *PredBB : predecessors(BB)) | |||
| 644 | PredecessorBlocks.insert(PredBB); | |||
| 645 | // If we have less predecessor blocks than predecessors then the phi will | |||
| 646 | // have more than one incoming value for the same block which we can't | |||
| 647 | // handle. | |||
| 648 | // TODO: This could be handled be erasing some of the duplicate incoming | |||
| 649 | // values. | |||
| 650 | if (PredecessorBlocks.size() != pred_size(BB)) | |||
| 651 | return false; | |||
| 652 | for (auto &Pair : HoistableBranches) { | |||
| 653 | if (Pair.second == BB) { | |||
| 654 | // Which blocks are predecessors via this branch depends on if the | |||
| 655 | // branch is triangle-like or diamond-like. | |||
| 656 | if (Pair.first->getSuccessor(0) == BB) { | |||
| 657 | PredecessorBlocks.erase(Pair.first->getParent()); | |||
| 658 | PredecessorBlocks.erase(Pair.first->getSuccessor(1)); | |||
| 659 | } else if (Pair.first->getSuccessor(1) == BB) { | |||
| 660 | PredecessorBlocks.erase(Pair.first->getParent()); | |||
| 661 | PredecessorBlocks.erase(Pair.first->getSuccessor(0)); | |||
| 662 | } else { | |||
| 663 | PredecessorBlocks.erase(Pair.first->getSuccessor(0)); | |||
| 664 | PredecessorBlocks.erase(Pair.first->getSuccessor(1)); | |||
| 665 | } | |||
| 666 | } | |||
| 667 | } | |||
| 668 | // PredecessorBlocks will now be empty if for every predecessor of BB we | |||
| 669 | // found a hoistable branch source. | |||
| 670 | return PredecessorBlocks.empty(); | |||
| 671 | } | |||
| 672 | ||||
| 673 | BasicBlock *getOrCreateHoistedBlock(BasicBlock *BB) { | |||
| 674 | if (!ControlFlowHoisting) | |||
| 675 | return CurLoop->getLoopPreheader(); | |||
| 676 | // If BB has already been hoisted, return that | |||
| 677 | if (HoistDestinationMap.count(BB)) | |||
| 678 | return HoistDestinationMap[BB]; | |||
| 679 | ||||
| 680 | // Check if this block is conditional based on a pending branch | |||
| 681 | auto HasBBAsSuccessor = | |||
| 682 | [&](DenseMap<BranchInst *, BasicBlock *>::value_type &Pair) { | |||
| 683 | return BB != Pair.second && (Pair.first->getSuccessor(0) == BB || | |||
| 684 | Pair.first->getSuccessor(1) == BB); | |||
| 685 | }; | |||
| 686 | auto It = std::find_if(HoistableBranches.begin(), HoistableBranches.end(), | |||
| 687 | HasBBAsSuccessor); | |||
| 688 | ||||
| 689 | // If not involved in a pending branch, hoist to preheader | |||
| 690 | BasicBlock *InitialPreheader = CurLoop->getLoopPreheader(); | |||
| 691 | if (It == HoistableBranches.end()) { | |||
| 692 | LLVM_DEBUG(dbgs() << "LICM using " << InitialPreheader->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM using " << InitialPreheader ->getName() << " as hoist destination for " << BB->getName() << "\n"; } } while (false) | |||
| 693 | << " as hoist destination for " << BB->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM using " << InitialPreheader ->getName() << " as hoist destination for " << BB->getName() << "\n"; } } while (false) | |||
| 694 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM using " << InitialPreheader ->getName() << " as hoist destination for " << BB->getName() << "\n"; } } while (false); | |||
| 695 | HoistDestinationMap[BB] = InitialPreheader; | |||
| 696 | return InitialPreheader; | |||
| 697 | } | |||
| 698 | BranchInst *BI = It->first; | |||
| 699 | assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) ==((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor ) == HoistableBranches.end() && "BB is expected to be the target of at most one branch" ) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 701, __PRETTY_FUNCTION__)) | |||
| 700 | HoistableBranches.end() &&((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor ) == HoistableBranches.end() && "BB is expected to be the target of at most one branch" ) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 701, __PRETTY_FUNCTION__)) | |||
| 701 | "BB is expected to be the target of at most one branch")((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor ) == HoistableBranches.end() && "BB is expected to be the target of at most one branch" ) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 701, __PRETTY_FUNCTION__)); | |||
| 702 | ||||
| 703 | LLVMContext &C = BB->getContext(); | |||
| 704 | BasicBlock *TrueDest = BI->getSuccessor(0); | |||
| 705 | BasicBlock *FalseDest = BI->getSuccessor(1); | |||
| 706 | BasicBlock *CommonSucc = HoistableBranches[BI]; | |||
| 707 | BasicBlock *HoistTarget = getOrCreateHoistedBlock(BI->getParent()); | |||
| 708 | ||||
| 709 | // Create hoisted versions of blocks that currently don't have them | |||
| 710 | auto CreateHoistedBlock = [&](BasicBlock *Orig) { | |||
| 711 | if (HoistDestinationMap.count(Orig)) | |||
| 712 | return HoistDestinationMap[Orig]; | |||
| 713 | BasicBlock *New = | |||
| 714 | BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent()); | |||
| 715 | HoistDestinationMap[Orig] = New; | |||
| 716 | DT->addNewBlock(New, HoistTarget); | |||
| 717 | if (CurLoop->getParentLoop()) | |||
| 718 | CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI); | |||
| 719 | ++NumCreatedBlocks; | |||
| 720 | LLVM_DEBUG(dbgs() << "LICM created " << New->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM created " << New-> getName() << " as hoist destination for " << Orig ->getName() << "\n"; } } while (false) | |||
| 721 | << " as hoist destination for " << Orig->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM created " << New-> getName() << " as hoist destination for " << Orig ->getName() << "\n"; } } while (false) | |||
| 722 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM created " << New-> getName() << " as hoist destination for " << Orig ->getName() << "\n"; } } while (false); | |||
| 723 | return New; | |||
| 724 | }; | |||
| 725 | BasicBlock *HoistTrueDest = CreateHoistedBlock(TrueDest); | |||
| 726 | BasicBlock *HoistFalseDest = CreateHoistedBlock(FalseDest); | |||
| 727 | BasicBlock *HoistCommonSucc = CreateHoistedBlock(CommonSucc); | |||
| 728 | ||||
| 729 | // Link up these blocks with branches. | |||
| 730 | if (!HoistCommonSucc->getTerminator()) { | |||
| 731 | // The new common successor we've generated will branch to whatever that | |||
| 732 | // hoist target branched to. | |||
| 733 | BasicBlock *TargetSucc = HoistTarget->getSingleSuccessor(); | |||
| 734 | assert(TargetSucc && "Expected hoist target to have a single successor")((TargetSucc && "Expected hoist target to have a single successor" ) ? static_cast<void> (0) : __assert_fail ("TargetSucc && \"Expected hoist target to have a single successor\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 734, __PRETTY_FUNCTION__)); | |||
| 735 | HoistCommonSucc->moveBefore(TargetSucc); | |||
| 736 | BranchInst::Create(TargetSucc, HoistCommonSucc); | |||
| 737 | } | |||
| 738 | if (!HoistTrueDest->getTerminator()) { | |||
| 739 | HoistTrueDest->moveBefore(HoistCommonSucc); | |||
| 740 | BranchInst::Create(HoistCommonSucc, HoistTrueDest); | |||
| 741 | } | |||
| 742 | if (!HoistFalseDest->getTerminator()) { | |||
| 743 | HoistFalseDest->moveBefore(HoistCommonSucc); | |||
| 744 | BranchInst::Create(HoistCommonSucc, HoistFalseDest); | |||
| 745 | } | |||
| 746 | ||||
| 747 | // If BI is being cloned to what was originally the preheader then | |||
| 748 | // HoistCommonSucc will now be the new preheader. | |||
| 749 | if (HoistTarget == InitialPreheader) { | |||
| 750 | // Phis in the loop header now need to use the new preheader. | |||
| 751 | InitialPreheader->replaceSuccessorsPhiUsesWith(HoistCommonSucc); | |||
| 752 | if (MSSAU) | |||
| 753 | MSSAU->wireOldPredecessorsToNewImmediatePredecessor( | |||
| 754 | HoistTarget->getSingleSuccessor(), HoistCommonSucc, {HoistTarget}); | |||
| 755 | // The new preheader dominates the loop header. | |||
| 756 | DomTreeNode *PreheaderNode = DT->getNode(HoistCommonSucc); | |||
| 757 | DomTreeNode *HeaderNode = DT->getNode(CurLoop->getHeader()); | |||
| 758 | DT->changeImmediateDominator(HeaderNode, PreheaderNode); | |||
| 759 | // The preheader hoist destination is now the new preheader, with the | |||
| 760 | // exception of the hoist destination of this branch. | |||
| 761 | for (auto &Pair : HoistDestinationMap) | |||
| 762 | if (Pair.second == InitialPreheader && Pair.first != BI->getParent()) | |||
| 763 | Pair.second = HoistCommonSucc; | |||
| 764 | } | |||
| 765 | ||||
| 766 | // Now finally clone BI. | |||
| 767 | ReplaceInstWithInst( | |||
| 768 | HoistTarget->getTerminator(), | |||
| 769 | BranchInst::Create(HoistTrueDest, HoistFalseDest, BI->getCondition())); | |||
| 770 | ++NumClonedBranches; | |||
| 771 | ||||
| 772 | assert(CurLoop->getLoopPreheader() &&((CurLoop->getLoopPreheader() && "Hoisting blocks should not have destroyed preheader" ) ? static_cast<void> (0) : __assert_fail ("CurLoop->getLoopPreheader() && \"Hoisting blocks should not have destroyed preheader\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 773, __PRETTY_FUNCTION__)) | |||
| 773 | "Hoisting blocks should not have destroyed preheader")((CurLoop->getLoopPreheader() && "Hoisting blocks should not have destroyed preheader" ) ? static_cast<void> (0) : __assert_fail ("CurLoop->getLoopPreheader() && \"Hoisting blocks should not have destroyed preheader\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 773, __PRETTY_FUNCTION__)); | |||
| 774 | return HoistDestinationMap[BB]; | |||
| 775 | } | |||
| 776 | }; | |||
| 777 | } // namespace | |||
| 778 | ||||
| 779 | /// Walk the specified region of the CFG (defined by all blocks dominated by | |||
| 780 | /// the specified block, and that are in the current loop) in depth first | |||
| 781 | /// order w.r.t the DominatorTree. This allows us to visit definitions before | |||
| 782 | /// uses, allowing us to hoist a loop body in one pass without iteration. | |||
| 783 | /// | |||
| 784 | bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, | |||
| 785 | DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop, | |||
| 786 | AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, | |||
| 787 | ICFLoopSafetyInfo *SafetyInfo, | |||
| 788 | SinkAndHoistLICMFlags &Flags, | |||
| 789 | OptimizationRemarkEmitter *ORE) { | |||
| 790 | // Verify inputs. | |||
| 791 | assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to hoistRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 793, __PRETTY_FUNCTION__)) | |||
| 792 | CurLoop != nullptr && SafetyInfo != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to hoistRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 793, __PRETTY_FUNCTION__)) | |||
| 793 | "Unexpected input to hoistRegion.")((N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && "Unexpected input to hoistRegion." ) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 793, __PRETTY_FUNCTION__)); | |||
| 794 | assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized." ) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 795, __PRETTY_FUNCTION__)) | |||
| 795 | "Either AliasSetTracker or MemorySSA should be initialized.")((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized." ) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 795, __PRETTY_FUNCTION__)); | |||
| 796 | ||||
| 797 | ControlFlowHoister CFH(LI, DT, CurLoop, MSSAU); | |||
| 798 | ||||
| 799 | // Keep track of instructions that have been hoisted, as they may need to be | |||
| 800 | // re-hoisted if they end up not dominating all of their uses. | |||
| 801 | SmallVector<Instruction *, 16> HoistedInstructions; | |||
| 802 | ||||
| 803 | // For PHI hoisting to work we need to hoist blocks before their successors. | |||
| 804 | // We can do this by iterating through the blocks in the loop in reverse | |||
| 805 | // post-order. | |||
| 806 | LoopBlocksRPO Worklist(CurLoop); | |||
| 807 | Worklist.perform(LI); | |||
| 808 | bool Changed = false; | |||
| 809 | for (BasicBlock *BB : Worklist) { | |||
| 810 | // Only need to process the contents of this block if it is not part of a | |||
| 811 | // subloop (which would already have been processed). | |||
| 812 | if (inSubLoop(BB, CurLoop, LI)) | |||
| 813 | continue; | |||
| 814 | ||||
| 815 | for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) { | |||
| 816 | Instruction &I = *II++; | |||
| 817 | // Try constant folding this instruction. If all the operands are | |||
| 818 | // constants, it is technically hoistable, but it would be better to | |||
| 819 | // just fold it. | |||
| 820 | if (Constant *C = ConstantFoldInstruction( | |||
| 821 | &I, I.getModule()->getDataLayout(), TLI)) { | |||
| 822 | LLVM_DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *Cdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n'; } } while (false) | |||
| 823 | << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n'; } } while (false); | |||
| 824 | if (CurAST) | |||
| 825 | CurAST->copyValue(&I, C); | |||
| 826 | // FIXME MSSA: Such replacements may make accesses unoptimized (D51960). | |||
| 827 | I.replaceAllUsesWith(C); | |||
| 828 | if (isInstructionTriviallyDead(&I, TLI)) | |||
| 829 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 830 | Changed = true; | |||
| 831 | continue; | |||
| 832 | } | |||
| 833 | ||||
| 834 | // Try hoisting the instruction out to the preheader. We can only do | |||
| 835 | // this if all of the operands of the instruction are loop invariant and | |||
| 836 | // if it is safe to hoist the instruction. | |||
| 837 | // TODO: It may be safe to hoist if we are hoisting to a conditional block | |||
| 838 | // and we have accurately duplicated the control flow from the loop header | |||
| 839 | // to that block. | |||
| 840 | if (CurLoop->hasLoopInvariantOperands(&I) && | |||
| 841 | canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, | |||
| 842 | ORE) && | |||
| 843 | isSafeToExecuteUnconditionally( | |||
| 844 | I, DT, CurLoop, SafetyInfo, ORE, | |||
| 845 | CurLoop->getLoopPreheader()->getTerminator())) { | |||
| 846 | hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 847 | MSSAU, ORE); | |||
| 848 | HoistedInstructions.push_back(&I); | |||
| 849 | Changed = true; | |||
| 850 | continue; | |||
| 851 | } | |||
| 852 | ||||
| 853 | // Attempt to remove floating point division out of the loop by | |||
| 854 | // converting it to a reciprocal multiplication. | |||
| 855 | if (I.getOpcode() == Instruction::FDiv && | |||
| 856 | CurLoop->isLoopInvariant(I.getOperand(1)) && | |||
| 857 | I.hasAllowReciprocal()) { | |||
| 858 | auto Divisor = I.getOperand(1); | |||
| 859 | auto One = llvm::ConstantFP::get(Divisor->getType(), 1.0); | |||
| 860 | auto ReciprocalDivisor = BinaryOperator::CreateFDiv(One, Divisor); | |||
| 861 | ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags()); | |||
| 862 | SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent()); | |||
| 863 | ReciprocalDivisor->insertBefore(&I); | |||
| 864 | ||||
| 865 | auto Product = | |||
| 866 | BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor); | |||
| 867 | Product->setFastMathFlags(I.getFastMathFlags()); | |||
| 868 | SafetyInfo->insertInstructionTo(Product, I.getParent()); | |||
| 869 | Product->insertAfter(&I); | |||
| 870 | I.replaceAllUsesWith(Product); | |||
| 871 | eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); | |||
| 872 | ||||
| 873 | hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), | |||
| 874 | SafetyInfo, MSSAU, ORE); | |||
| 875 | HoistedInstructions.push_back(ReciprocalDivisor); | |||
| 876 | Changed = true; | |||
| 877 | continue; | |||
| 878 | } | |||
| 879 | ||||
| 880 | auto IsInvariantStart = [&](Instruction &I) { | |||
| 881 | using namespace PatternMatch; | |||
| 882 | return I.use_empty() && | |||
| 883 | match(&I, m_Intrinsic<Intrinsic::invariant_start>()); | |||
| 884 | }; | |||
| 885 | auto MustExecuteWithoutWritesBefore = [&](Instruction &I) { | |||
| 886 | return SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) && | |||
| 887 | SafetyInfo->doesNotWriteMemoryBefore(I, CurLoop); | |||
| 888 | }; | |||
| 889 | if ((IsInvariantStart(I) || isGuard(&I)) && | |||
| 890 | CurLoop->hasLoopInvariantOperands(&I) && | |||
| 891 | MustExecuteWithoutWritesBefore(I)) { | |||
| 892 | hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 893 | MSSAU, ORE); | |||
| 894 | HoistedInstructions.push_back(&I); | |||
| 895 | Changed = true; | |||
| 896 | continue; | |||
| 897 | } | |||
| 898 | ||||
| 899 | if (PHINode *PN = dyn_cast<PHINode>(&I)) { | |||
| 900 | if (CFH.canHoistPHI(PN)) { | |||
| 901 | // Redirect incoming blocks first to ensure that we create hoisted | |||
| 902 | // versions of those blocks before we hoist the phi. | |||
| 903 | for (unsigned int i = 0; i < PN->getNumIncomingValues(); ++i) | |||
| 904 | PN->setIncomingBlock( | |||
| 905 | i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i))); | |||
| 906 | hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, | |||
| 907 | MSSAU, ORE); | |||
| 908 | assert(DT->dominates(PN, BB) && "Conditional PHIs not expected")((DT->dominates(PN, BB) && "Conditional PHIs not expected" ) ? static_cast<void> (0) : __assert_fail ("DT->dominates(PN, BB) && \"Conditional PHIs not expected\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 908, __PRETTY_FUNCTION__)); | |||
| 909 | Changed = true; | |||
| 910 | continue; | |||
| 911 | } | |||
| 912 | } | |||
| 913 | ||||
| 914 | // Remember possibly hoistable branches so we can actually hoist them | |||
| 915 | // later if needed. | |||
| 916 | if (BranchInst *BI = dyn_cast<BranchInst>(&I)) | |||
| 917 | CFH.registerPossiblyHoistableBranch(BI); | |||
| 918 | } | |||
| 919 | } | |||
| 920 | ||||
| 921 | // If we hoisted instructions to a conditional block they may not dominate | |||
| 922 | // their uses that weren't hoisted (such as phis where some operands are not | |||
| 923 | // loop invariant). If so make them unconditional by moving them to their | |||
| 924 | // immediate dominator. We iterate through the instructions in reverse order | |||
| 925 | // which ensures that when we rehoist an instruction we rehoist its operands, | |||
| 926 | // and also keep track of where in the block we are rehoisting to to make sure | |||
| 927 | // that we rehoist instructions before the instructions that use them. | |||
| 928 | Instruction *HoistPoint = nullptr; | |||
| 929 | if (ControlFlowHoisting) { | |||
| 930 | for (Instruction *I : reverse(HoistedInstructions)) { | |||
| 931 | if (!llvm::all_of(I->uses(), | |||
| 932 | [&](Use &U) { return DT->dominates(I, U); })) { | |||
| 933 | BasicBlock *Dominator = | |||
| 934 | DT->getNode(I->getParent())->getIDom()->getBlock(); | |||
| 935 | if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) { | |||
| 936 | if (HoistPoint) | |||
| 937 | assert(DT->dominates(Dominator, HoistPoint->getParent()) &&((DT->dominates(Dominator, HoistPoint->getParent()) && "New hoist point expected to dominate old hoist point") ? static_cast <void> (0) : __assert_fail ("DT->dominates(Dominator, HoistPoint->getParent()) && \"New hoist point expected to dominate old hoist point\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 938, __PRETTY_FUNCTION__)) | |||
| 938 | "New hoist point expected to dominate old hoist point")((DT->dominates(Dominator, HoistPoint->getParent()) && "New hoist point expected to dominate old hoist point") ? static_cast <void> (0) : __assert_fail ("DT->dominates(Dominator, HoistPoint->getParent()) && \"New hoist point expected to dominate old hoist point\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 938, __PRETTY_FUNCTION__)); | |||
| 939 | HoistPoint = Dominator->getTerminator(); | |||
| 940 | } | |||
| 941 | LLVM_DEBUG(dbgs() << "LICM rehoisting to "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint ->getParent()->getName() << ": " << *I << "\n"; } } while (false) | |||
| 942 | << HoistPoint->getParent()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint ->getParent()->getName() << ": " << *I << "\n"; } } while (false) | |||
| 943 | << ": " << *I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint ->getParent()->getName() << ": " << *I << "\n"; } } while (false); | |||
| 944 | moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU); | |||
| 945 | HoistPoint = I; | |||
| 946 | Changed = true; | |||
| 947 | } | |||
| 948 | } | |||
| 949 | } | |||
| 950 | if (MSSAU && VerifyMemorySSA) | |||
| 951 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 952 | ||||
| 953 | // Now that we've finished hoisting make sure that LI and DT are still | |||
| 954 | // valid. | |||
| 955 | #ifndef NDEBUG | |||
| 956 | if (Changed) { | |||
| 957 | assert(DT->verify(DominatorTree::VerificationLevel::Fast) &&((DT->verify(DominatorTree::VerificationLevel::Fast) && "Dominator tree verification failed") ? static_cast<void> (0) : __assert_fail ("DT->verify(DominatorTree::VerificationLevel::Fast) && \"Dominator tree verification failed\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 958, __PRETTY_FUNCTION__)) | |||
| 958 | "Dominator tree verification failed")((DT->verify(DominatorTree::VerificationLevel::Fast) && "Dominator tree verification failed") ? static_cast<void> (0) : __assert_fail ("DT->verify(DominatorTree::VerificationLevel::Fast) && \"Dominator tree verification failed\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 958, __PRETTY_FUNCTION__)); | |||
| 959 | LI->verify(*DT); | |||
| 960 | } | |||
| 961 | #endif | |||
| 962 | ||||
| 963 | return Changed; | |||
| 964 | } | |||
| 965 | ||||
| 966 | // Return true if LI is invariant within scope of the loop. LI is invariant if | |||
| 967 | // CurLoop is dominated by an invariant.start representing the same memory | |||
| 968 | // location and size as the memory location LI loads from, and also the | |||
| 969 | // invariant.start has no uses. | |||
| 970 | static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT, | |||
| 971 | Loop *CurLoop) { | |||
| 972 | Value *Addr = LI->getOperand(0); | |||
| 973 | const DataLayout &DL = LI->getModule()->getDataLayout(); | |||
| 974 | const uint32_t LocSizeInBits = DL.getTypeSizeInBits( | |||
| 975 | cast<PointerType>(Addr->getType())->getElementType()); | |||
| 976 | ||||
| 977 | // if the type is i8 addrspace(x)*, we know this is the type of | |||
| 978 | // llvm.invariant.start operand | |||
| 979 | auto *PtrInt8Ty = PointerType::get(Type::getInt8Ty(LI->getContext()), | |||
| 980 | LI->getPointerAddressSpace()); | |||
| 981 | unsigned BitcastsVisited = 0; | |||
| 982 | // Look through bitcasts until we reach the i8* type (this is invariant.start | |||
| 983 | // operand type). | |||
| 984 | while (Addr->getType() != PtrInt8Ty) { | |||
| 985 | auto *BC = dyn_cast<BitCastInst>(Addr); | |||
| 986 | // Avoid traversing high number of bitcast uses. | |||
| 987 | if (++BitcastsVisited > MaxNumUsesTraversed || !BC) | |||
| 988 | return false; | |||
| 989 | Addr = BC->getOperand(0); | |||
| 990 | } | |||
| 991 | ||||
| 992 | unsigned UsesVisited = 0; | |||
| 993 | // Traverse all uses of the load operand value, to see if invariant.start is | |||
| 994 | // one of the uses, and whether it dominates the load instruction. | |||
| 995 | for (auto *U : Addr->users()) { | |||
| 996 | // Avoid traversing for Load operand with high number of users. | |||
| 997 | if (++UsesVisited > MaxNumUsesTraversed) | |||
| 998 | return false; | |||
| 999 | IntrinsicInst *II = dyn_cast<IntrinsicInst>(U); | |||
| 1000 | // If there are escaping uses of invariant.start instruction, the load maybe | |||
| 1001 | // non-invariant. | |||
| 1002 | if (!II || II->getIntrinsicID() != Intrinsic::invariant_start || | |||
| 1003 | !II->use_empty()) | |||
| 1004 | continue; | |||
| 1005 | unsigned InvariantSizeInBits = | |||
| 1006 | cast<ConstantInt>(II->getArgOperand(0))->getSExtValue() * 8; | |||
| 1007 | // Confirm the invariant.start location size contains the load operand size | |||
| 1008 | // in bits. Also, the invariant.start should dominate the load, and we | |||
| 1009 | // should not hoist the load out of a loop that contains this dominating | |||
| 1010 | // invariant.start. | |||
| 1011 | if (LocSizeInBits <= InvariantSizeInBits && | |||
| 1012 | DT->properlyDominates(II->getParent(), CurLoop->getHeader())) | |||
| 1013 | return true; | |||
| 1014 | } | |||
| 1015 | ||||
| 1016 | return false; | |||
| 1017 | } | |||
| 1018 | ||||
| 1019 | namespace { | |||
| 1020 | /// Return true if-and-only-if we know how to (mechanically) both hoist and | |||
| 1021 | /// sink a given instruction out of a loop. Does not address legality | |||
| 1022 | /// concerns such as aliasing or speculation safety. | |||
| 1023 | bool isHoistableAndSinkableInst(Instruction &I) { | |||
| 1024 | // Only these instructions are hoistable/sinkable. | |||
| 1025 | return (isa<LoadInst>(I) || isa<StoreInst>(I) || isa<CallInst>(I) || | |||
| 1026 | isa<FenceInst>(I) || isa<BinaryOperator>(I) || isa<CastInst>(I) || | |||
| 1027 | isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || | |||
| 1028 | isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || | |||
| 1029 | isa<ShuffleVectorInst>(I) || isa<ExtractValueInst>(I) || | |||
| 1030 | isa<InsertValueInst>(I)); | |||
| 1031 | } | |||
| 1032 | /// Return true if all of the alias sets within this AST are known not to | |||
| 1033 | /// contain a Mod, or if MSSA knows thare are no MemoryDefs in the loop. | |||
| 1034 | bool isReadOnly(AliasSetTracker *CurAST, const MemorySSAUpdater *MSSAU, | |||
| 1035 | const Loop *L) { | |||
| 1036 | if (CurAST) { | |||
| 1037 | for (AliasSet &AS : *CurAST) { | |||
| 1038 | if (!AS.isForwardingAliasSet() && AS.isMod()) { | |||
| 1039 | return false; | |||
| 1040 | } | |||
| 1041 | } | |||
| 1042 | return true; | |||
| 1043 | } else { /*MSSAU*/ | |||
| 1044 | for (auto *BB : L->getBlocks()) | |||
| 1045 | if (MSSAU->getMemorySSA()->getBlockDefs(BB)) | |||
| 1046 | return false; | |||
| 1047 | return true; | |||
| 1048 | } | |||
| 1049 | } | |||
| 1050 | ||||
| 1051 | /// Return true if I is the only Instruction with a MemoryAccess in L. | |||
| 1052 | bool isOnlyMemoryAccess(const Instruction *I, const Loop *L, | |||
| 1053 | const MemorySSAUpdater *MSSAU) { | |||
| 1054 | for (auto *BB : L->getBlocks()) | |||
| 1055 | if (auto *Accs = MSSAU->getMemorySSA()->getBlockAccesses(BB)) { | |||
| 1056 | int NotAPhi = 0; | |||
| 1057 | for (const auto &Acc : *Accs) { | |||
| 1058 | if (isa<MemoryPhi>(&Acc)) | |||
| 1059 | continue; | |||
| 1060 | const auto *MUD = cast<MemoryUseOrDef>(&Acc); | |||
| 1061 | if (MUD->getMemoryInst() != I || NotAPhi++ == 1) | |||
| 1062 | return false; | |||
| 1063 | } | |||
| 1064 | } | |||
| 1065 | return true; | |||
| 1066 | } | |||
| 1067 | } | |||
| 1068 | ||||
| 1069 | bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, | |||
| 1070 | Loop *CurLoop, AliasSetTracker *CurAST, | |||
| 1071 | MemorySSAUpdater *MSSAU, | |||
| 1072 | bool TargetExecutesOncePerLoop, | |||
| 1073 | SinkAndHoistLICMFlags *Flags, | |||
| 1074 | OptimizationRemarkEmitter *ORE) { | |||
| 1075 | // If we don't understand the instruction, bail early. | |||
| 1076 | if (!isHoistableAndSinkableInst(I)) | |||
| ||||
| 1077 | return false; | |||
| 1078 | ||||
| 1079 | MemorySSA *MSSA = MSSAU ? MSSAU->getMemorySSA() : nullptr; | |||
| 1080 | if (MSSA) | |||
| 1081 | assert(Flags != nullptr && "Flags cannot be null.")((Flags != nullptr && "Flags cannot be null.") ? static_cast <void> (0) : __assert_fail ("Flags != nullptr && \"Flags cannot be null.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1081, __PRETTY_FUNCTION__)); | |||
| 1082 | ||||
| 1083 | // Loads have extra constraints we have to verify before we can hoist them. | |||
| 1084 | if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { | |||
| 1085 | if (!LI->isUnordered()) | |||
| 1086 | return false; // Don't sink/hoist volatile or ordered atomic loads! | |||
| 1087 | ||||
| 1088 | // Loads from constant memory are always safe to move, even if they end up | |||
| 1089 | // in the same alias set as something that ends up being modified. | |||
| 1090 | if (AA->pointsToConstantMemory(LI->getOperand(0))) | |||
| 1091 | return true; | |||
| 1092 | if (LI->getMetadata(LLVMContext::MD_invariant_load)) | |||
| 1093 | return true; | |||
| 1094 | ||||
| 1095 | if (LI->isAtomic() && !TargetExecutesOncePerLoop) | |||
| 1096 | return false; // Don't risk duplicating unordered loads | |||
| 1097 | ||||
| 1098 | // This checks for an invariant.start dominating the load. | |||
| 1099 | if (isLoadInvariantInLoop(LI, DT, CurLoop)) | |||
| 1100 | return true; | |||
| 1101 | ||||
| 1102 | bool Invalidated; | |||
| 1103 | if (CurAST) | |||
| 1104 | Invalidated = pointerInvalidatedByLoop(MemoryLocation::get(LI), CurAST, | |||
| 1105 | CurLoop, AA); | |||
| 1106 | else | |||
| 1107 | Invalidated = pointerInvalidatedByLoopWithMSSA( | |||
| 1108 | MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(LI)), CurLoop, *Flags); | |||
| 1109 | // Check loop-invariant address because this may also be a sinkable load | |||
| 1110 | // whose address is not necessarily loop-invariant. | |||
| 1111 | if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand())) | |||
| 1112 | ORE->emit([&]() { | |||
| 1113 | return OptimizationRemarkMissed( | |||
| 1114 | DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressInvalidated", LI) | |||
| 1115 | << "failed to move load with loop-invariant address " | |||
| 1116 | "because the loop may invalidate its value"; | |||
| 1117 | }); | |||
| 1118 | ||||
| 1119 | return !Invalidated; | |||
| 1120 | } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { | |||
| 1121 | // Don't sink or hoist dbg info; it's legal, but not useful. | |||
| 1122 | if (isa<DbgInfoIntrinsic>(I)) | |||
| 1123 | return false; | |||
| 1124 | ||||
| 1125 | // Don't sink calls which can throw. | |||
| 1126 | if (CI->mayThrow()) | |||
| 1127 | return false; | |||
| 1128 | ||||
| 1129 | using namespace PatternMatch; | |||
| 1130 | if (match(CI, m_Intrinsic<Intrinsic::assume>())) | |||
| 1131 | // Assumes don't actually alias anything or throw | |||
| 1132 | return true; | |||
| 1133 | ||||
| 1134 | // Handle simple cases by querying alias analysis. | |||
| 1135 | FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI); | |||
| 1136 | if (Behavior == FMRB_DoesNotAccessMemory) | |||
| 1137 | return true; | |||
| 1138 | if (AliasAnalysis::onlyReadsMemory(Behavior)) { | |||
| 1139 | // A readonly argmemonly function only reads from memory pointed to by | |||
| 1140 | // it's arguments with arbitrary offsets. If we can prove there are no | |||
| 1141 | // writes to this memory in the loop, we can hoist or sink. | |||
| 1142 | if (AliasAnalysis::onlyAccessesArgPointees(Behavior)) { | |||
| 1143 | // TODO: expand to writeable arguments | |||
| 1144 | for (Value *Op : CI->arg_operands()) | |||
| 1145 | if (Op->getType()->isPointerTy()) { | |||
| 1146 | bool Invalidated; | |||
| 1147 | if (CurAST) | |||
| 1148 | Invalidated = pointerInvalidatedByLoop( | |||
| 1149 | MemoryLocation(Op, LocationSize::unknown(), AAMDNodes()), | |||
| 1150 | CurAST, CurLoop, AA); | |||
| 1151 | else | |||
| 1152 | Invalidated = pointerInvalidatedByLoopWithMSSA( | |||
| 1153 | MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(CI)), CurLoop, | |||
| 1154 | *Flags); | |||
| 1155 | if (Invalidated) | |||
| 1156 | return false; | |||
| 1157 | } | |||
| 1158 | return true; | |||
| 1159 | } | |||
| 1160 | ||||
| 1161 | // If this call only reads from memory and there are no writes to memory | |||
| 1162 | // in the loop, we can hoist or sink the call as appropriate. | |||
| 1163 | if (isReadOnly(CurAST, MSSAU, CurLoop)) | |||
| 1164 | return true; | |||
| 1165 | } | |||
| 1166 | ||||
| 1167 | // FIXME: This should use mod/ref information to see if we can hoist or | |||
| 1168 | // sink the call. | |||
| 1169 | ||||
| 1170 | return false; | |||
| 1171 | } else if (auto *FI = dyn_cast<FenceInst>(&I)) { | |||
| 1172 | // Fences alias (most) everything to provide ordering. For the moment, | |||
| 1173 | // just give up if there are any other memory operations in the loop. | |||
| 1174 | if (CurAST) { | |||
| 1175 | auto Begin = CurAST->begin(); | |||
| 1176 | assert(Begin != CurAST->end() && "must contain FI")((Begin != CurAST->end() && "must contain FI") ? static_cast <void> (0) : __assert_fail ("Begin != CurAST->end() && \"must contain FI\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1176, __PRETTY_FUNCTION__)); | |||
| 1177 | if (std::next(Begin) != CurAST->end()) | |||
| 1178 | // constant memory for instance, TODO: handle better | |||
| 1179 | return false; | |||
| 1180 | auto *UniqueI = Begin->getUniqueInstruction(); | |||
| 1181 | if (!UniqueI) | |||
| 1182 | // other memory op, give up | |||
| 1183 | return false; | |||
| 1184 | (void)FI; // suppress unused variable warning | |||
| 1185 | assert(UniqueI == FI && "AS must contain FI")((UniqueI == FI && "AS must contain FI") ? static_cast <void> (0) : __assert_fail ("UniqueI == FI && \"AS must contain FI\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1185, __PRETTY_FUNCTION__)); | |||
| 1186 | return true; | |||
| 1187 | } else // MSSAU | |||
| 1188 | return isOnlyMemoryAccess(FI, CurLoop, MSSAU); | |||
| 1189 | } else if (auto *SI = dyn_cast<StoreInst>(&I)) { | |||
| 1190 | if (!SI->isUnordered()) | |||
| 1191 | return false; // Don't sink/hoist volatile or ordered atomic store! | |||
| 1192 | ||||
| 1193 | // We can only hoist a store that we can prove writes a value which is not | |||
| 1194 | // read or overwritten within the loop. For those cases, we fallback to | |||
| 1195 | // load store promotion instead. TODO: We can extend this to cases where | |||
| 1196 | // there is exactly one write to the location and that write dominates an | |||
| 1197 | // arbitrary number of reads in the loop. | |||
| 1198 | if (CurAST) { | |||
| 1199 | auto &AS = CurAST->getAliasSetFor(MemoryLocation::get(SI)); | |||
| 1200 | ||||
| 1201 | if (AS.isRef() || !AS.isMustAlias()) | |||
| 1202 | // Quick exit test, handled by the full path below as well. | |||
| 1203 | return false; | |||
| 1204 | auto *UniqueI = AS.getUniqueInstruction(); | |||
| 1205 | if (!UniqueI) | |||
| 1206 | // other memory op, give up | |||
| 1207 | return false; | |||
| 1208 | assert(UniqueI == SI && "AS must contain SI")((UniqueI == SI && "AS must contain SI") ? static_cast <void> (0) : __assert_fail ("UniqueI == SI && \"AS must contain SI\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1208, __PRETTY_FUNCTION__)); | |||
| 1209 | return true; | |||
| 1210 | } else { // MSSAU | |||
| 1211 | if (isOnlyMemoryAccess(SI, CurLoop, MSSAU)) | |||
| 1212 | return true; | |||
| 1213 | // If there are more accesses than the Promotion cap, give up, we're not | |||
| 1214 | // walking a list that long. | |||
| 1215 | if (Flags->NoOfMemAccTooLarge) | |||
| 1216 | return false; | |||
| 1217 | // Check store only if there's still "quota" to check clobber. | |||
| 1218 | if (Flags->LicmMssaOptCounter >= Flags->LicmMssaOptCap) | |||
| 1219 | return false; | |||
| 1220 | // If there are interfering Uses (i.e. their defining access is in the | |||
| 1221 | // loop), or ordered loads (stored as Defs!), don't move this store. | |||
| 1222 | // Could do better here, but this is conservatively correct. | |||
| 1223 | // TODO: Cache set of Uses on the first walk in runOnLoop, update when | |||
| 1224 | // moving accesses. Can also extend to dominating uses. | |||
| 1225 | for (auto *BB : CurLoop->getBlocks()) | |||
| 1226 | if (auto *Accesses = MSSA->getBlockAccesses(BB)) { | |||
| 1227 | for (const auto &MA : *Accesses) | |||
| 1228 | if (const auto *MU = dyn_cast<MemoryUse>(&MA)) { | |||
| 1229 | auto *MD = MU->getDefiningAccess(); | |||
| 1230 | if (!MSSA->isLiveOnEntryDef(MD) && | |||
| 1231 | CurLoop->contains(MD->getBlock())) | |||
| 1232 | return false; | |||
| 1233 | } else if (const auto *MD = dyn_cast<MemoryDef>(&MA)) | |||
| 1234 | if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) { | |||
| 1235 | (void)LI; // Silence warning. | |||
| 1236 | assert(!LI->isUnordered() && "Expected unordered load")((!LI->isUnordered() && "Expected unordered load") ? static_cast<void> (0) : __assert_fail ("!LI->isUnordered() && \"Expected unordered load\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1236, __PRETTY_FUNCTION__)); | |||
| 1237 | return false; | |||
| 1238 | } | |||
| 1239 | } | |||
| 1240 | ||||
| 1241 | auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI); | |||
| ||||
| 1242 | Flags->LicmMssaOptCounter++; | |||
| 1243 | // If there are no clobbering Defs in the loop, store is safe to hoist. | |||
| 1244 | return MSSA->isLiveOnEntryDef(Source) || | |||
| 1245 | !CurLoop->contains(Source->getBlock()); | |||
| 1246 | } | |||
| 1247 | } | |||
| 1248 | ||||
| 1249 | assert(!I.mayReadOrWriteMemory() && "unhandled aliasing")((!I.mayReadOrWriteMemory() && "unhandled aliasing") ? static_cast<void> (0) : __assert_fail ("!I.mayReadOrWriteMemory() && \"unhandled aliasing\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1249, __PRETTY_FUNCTION__)); | |||
| 1250 | ||||
| 1251 | // We've established mechanical ability and aliasing, it's up to the caller | |||
| 1252 | // to check fault safety | |||
| 1253 | return true; | |||
| 1254 | } | |||
| 1255 | ||||
| 1256 | /// Returns true if a PHINode is a trivially replaceable with an | |||
| 1257 | /// Instruction. | |||
| 1258 | /// This is true when all incoming values are that instruction. | |||
| 1259 | /// This pattern occurs most often with LCSSA PHI nodes. | |||
| 1260 | /// | |||
| 1261 | static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) { | |||
| 1262 | for (const Value *IncValue : PN.incoming_values()) | |||
| 1263 | if (IncValue != &I) | |||
| 1264 | return false; | |||
| 1265 | ||||
| 1266 | return true; | |||
| 1267 | } | |||
| 1268 | ||||
| 1269 | /// Return true if the instruction is free in the loop. | |||
| 1270 | static bool isFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 1271 | const TargetTransformInfo *TTI) { | |||
| 1272 | ||||
| 1273 | if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I)) { | |||
| 1274 | if (TTI->getUserCost(GEP) != TargetTransformInfo::TCC_Free) | |||
| 1275 | return false; | |||
| 1276 | // For a GEP, we cannot simply use getUserCost because currently it | |||
| 1277 | // optimistically assume that a GEP will fold into addressing mode | |||
| 1278 | // regardless of its users. | |||
| 1279 | const BasicBlock *BB = GEP->getParent(); | |||
| 1280 | for (const User *U : GEP->users()) { | |||
| 1281 | const Instruction *UI = cast<Instruction>(U); | |||
| 1282 | if (CurLoop->contains(UI) && | |||
| 1283 | (BB != UI->getParent() || | |||
| 1284 | (!isa<StoreInst>(UI) && !isa<LoadInst>(UI)))) | |||
| 1285 | return false; | |||
| 1286 | } | |||
| 1287 | return true; | |||
| 1288 | } else | |||
| 1289 | return TTI->getUserCost(&I) == TargetTransformInfo::TCC_Free; | |||
| 1290 | } | |||
| 1291 | ||||
| 1292 | /// Return true if the only users of this instruction are outside of | |||
| 1293 | /// the loop. If this is true, we can sink the instruction to the exit | |||
| 1294 | /// blocks of the loop. | |||
| 1295 | /// | |||
| 1296 | /// We also return true if the instruction could be folded away in lowering. | |||
| 1297 | /// (e.g., a GEP can be folded into a load as an addressing mode in the loop). | |||
| 1298 | static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, | |||
| 1299 | const LoopSafetyInfo *SafetyInfo, | |||
| 1300 | TargetTransformInfo *TTI, bool &FreeInLoop) { | |||
| 1301 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1302 | bool IsFree = isFreeInLoop(I, CurLoop, TTI); | |||
| 1303 | for (const User *U : I.users()) { | |||
| 1304 | const Instruction *UI = cast<Instruction>(U); | |||
| 1305 | if (const PHINode *PN = dyn_cast<PHINode>(UI)) { | |||
| 1306 | const BasicBlock *BB = PN->getParent(); | |||
| 1307 | // We cannot sink uses in catchswitches. | |||
| 1308 | if (isa<CatchSwitchInst>(BB->getTerminator())) | |||
| 1309 | return false; | |||
| 1310 | ||||
| 1311 | // We need to sink a callsite to a unique funclet. Avoid sinking if the | |||
| 1312 | // phi use is too muddled. | |||
| 1313 | if (isa<CallInst>(I)) | |||
| 1314 | if (!BlockColors.empty() && | |||
| 1315 | BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1) | |||
| 1316 | return false; | |||
| 1317 | } | |||
| 1318 | ||||
| 1319 | if (CurLoop->contains(UI)) { | |||
| 1320 | if (IsFree) { | |||
| 1321 | FreeInLoop = true; | |||
| 1322 | continue; | |||
| 1323 | } | |||
| 1324 | return false; | |||
| 1325 | } | |||
| 1326 | } | |||
| 1327 | return true; | |||
| 1328 | } | |||
| 1329 | ||||
| 1330 | static Instruction *CloneInstructionInExitBlock( | |||
| 1331 | Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, | |||
| 1332 | const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) { | |||
| 1333 | Instruction *New; | |||
| 1334 | if (auto *CI = dyn_cast<CallInst>(&I)) { | |||
| 1335 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1336 | ||||
| 1337 | // Sinking call-sites need to be handled differently from other | |||
| 1338 | // instructions. The cloned call-site needs a funclet bundle operand | |||
| 1339 | // appropriate for its location in the CFG. | |||
| 1340 | SmallVector<OperandBundleDef, 1> OpBundles; | |||
| 1341 | for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles(); | |||
| 1342 | BundleIdx != BundleEnd; ++BundleIdx) { | |||
| 1343 | OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx); | |||
| 1344 | if (Bundle.getTagID() == LLVMContext::OB_funclet) | |||
| 1345 | continue; | |||
| 1346 | ||||
| 1347 | OpBundles.emplace_back(Bundle); | |||
| 1348 | } | |||
| 1349 | ||||
| 1350 | if (!BlockColors.empty()) { | |||
| 1351 | const ColorVector &CV = BlockColors.find(&ExitBlock)->second; | |||
| 1352 | assert(CV.size() == 1 && "non-unique color for exit block!")((CV.size() == 1 && "non-unique color for exit block!" ) ? static_cast<void> (0) : __assert_fail ("CV.size() == 1 && \"non-unique color for exit block!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1352, __PRETTY_FUNCTION__)); | |||
| 1353 | BasicBlock *BBColor = CV.front(); | |||
| 1354 | Instruction *EHPad = BBColor->getFirstNonPHI(); | |||
| 1355 | if (EHPad->isEHPad()) | |||
| 1356 | OpBundles.emplace_back("funclet", EHPad); | |||
| 1357 | } | |||
| 1358 | ||||
| 1359 | New = CallInst::Create(CI, OpBundles); | |||
| 1360 | } else { | |||
| 1361 | New = I.clone(); | |||
| 1362 | } | |||
| 1363 | ||||
| 1364 | ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New); | |||
| 1365 | if (!I.getName().empty()) | |||
| 1366 | New->setName(I.getName() + ".le"); | |||
| 1367 | ||||
| 1368 | MemoryAccess *OldMemAcc; | |||
| 1369 | if (MSSAU && (OldMemAcc = MSSAU->getMemorySSA()->getMemoryAccess(&I))) { | |||
| 1370 | // Create a new MemoryAccess and let MemorySSA set its defining access. | |||
| 1371 | MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB( | |||
| 1372 | New, nullptr, New->getParent(), MemorySSA::Beginning); | |||
| 1373 | if (NewMemAcc) { | |||
| 1374 | if (auto *MemDef = dyn_cast<MemoryDef>(NewMemAcc)) | |||
| 1375 | MSSAU->insertDef(MemDef, /*RenameUses=*/true); | |||
| 1376 | else { | |||
| 1377 | auto *MemUse = cast<MemoryUse>(NewMemAcc); | |||
| 1378 | MSSAU->insertUse(MemUse); | |||
| 1379 | } | |||
| 1380 | } | |||
| 1381 | } | |||
| 1382 | ||||
| 1383 | // Build LCSSA PHI nodes for any in-loop operands. Note that this is | |||
| 1384 | // particularly cheap because we can rip off the PHI node that we're | |||
| 1385 | // replacing for the number and blocks of the predecessors. | |||
| 1386 | // OPT: If this shows up in a profile, we can instead finish sinking all | |||
| 1387 | // invariant instructions, and then walk their operands to re-establish | |||
| 1388 | // LCSSA. That will eliminate creating PHI nodes just to nuke them when | |||
| 1389 | // sinking bottom-up. | |||
| 1390 | for (User::op_iterator OI = New->op_begin(), OE = New->op_end(); OI != OE; | |||
| 1391 | ++OI) | |||
| 1392 | if (Instruction *OInst = dyn_cast<Instruction>(*OI)) | |||
| 1393 | if (Loop *OLoop = LI->getLoopFor(OInst->getParent())) | |||
| 1394 | if (!OLoop->contains(&PN)) { | |||
| 1395 | PHINode *OpPN = | |||
| 1396 | PHINode::Create(OInst->getType(), PN.getNumIncomingValues(), | |||
| 1397 | OInst->getName() + ".lcssa", &ExitBlock.front()); | |||
| 1398 | for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) | |||
| 1399 | OpPN->addIncoming(OInst, PN.getIncomingBlock(i)); | |||
| 1400 | *OI = OpPN; | |||
| 1401 | } | |||
| 1402 | return New; | |||
| 1403 | } | |||
| 1404 | ||||
| 1405 | static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, | |||
| 1406 | AliasSetTracker *AST, MemorySSAUpdater *MSSAU) { | |||
| 1407 | if (AST) | |||
| 1408 | AST->deleteValue(&I); | |||
| 1409 | if (MSSAU) | |||
| 1410 | MSSAU->removeMemoryAccess(&I); | |||
| 1411 | SafetyInfo.removeInstruction(&I); | |||
| 1412 | I.eraseFromParent(); | |||
| 1413 | } | |||
| 1414 | ||||
| 1415 | static void moveInstructionBefore(Instruction &I, Instruction &Dest, | |||
| 1416 | ICFLoopSafetyInfo &SafetyInfo, | |||
| 1417 | MemorySSAUpdater *MSSAU) { | |||
| 1418 | SafetyInfo.removeInstruction(&I); | |||
| 1419 | SafetyInfo.insertInstructionTo(&I, Dest.getParent()); | |||
| 1420 | I.moveBefore(&Dest); | |||
| 1421 | if (MSSAU) | |||
| 1422 | if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>( | |||
| 1423 | MSSAU->getMemorySSA()->getMemoryAccess(&I))) | |||
| 1424 | MSSAU->moveToPlace(OldMemAcc, Dest.getParent(), MemorySSA::End); | |||
| 1425 | } | |||
| 1426 | ||||
| 1427 | static Instruction *sinkThroughTriviallyReplaceablePHI( | |||
| 1428 | PHINode *TPN, Instruction *I, LoopInfo *LI, | |||
| 1429 | SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies, | |||
| 1430 | const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop, | |||
| 1431 | MemorySSAUpdater *MSSAU) { | |||
| 1432 | assert(isTriviallyReplaceablePHI(*TPN, *I) &&((isTriviallyReplaceablePHI(*TPN, *I) && "Expect only trivially replaceable PHI" ) ? static_cast<void> (0) : __assert_fail ("isTriviallyReplaceablePHI(*TPN, *I) && \"Expect only trivially replaceable PHI\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1433, __PRETTY_FUNCTION__)) | |||
| 1433 | "Expect only trivially replaceable PHI")((isTriviallyReplaceablePHI(*TPN, *I) && "Expect only trivially replaceable PHI" ) ? static_cast<void> (0) : __assert_fail ("isTriviallyReplaceablePHI(*TPN, *I) && \"Expect only trivially replaceable PHI\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1433, __PRETTY_FUNCTION__)); | |||
| 1434 | BasicBlock *ExitBlock = TPN->getParent(); | |||
| 1435 | Instruction *New; | |||
| 1436 | auto It = SunkCopies.find(ExitBlock); | |||
| 1437 | if (It != SunkCopies.end()) | |||
| 1438 | New = It->second; | |||
| 1439 | else | |||
| 1440 | New = SunkCopies[ExitBlock] = CloneInstructionInExitBlock( | |||
| 1441 | *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU); | |||
| 1442 | return New; | |||
| 1443 | } | |||
| 1444 | ||||
| 1445 | static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) { | |||
| 1446 | BasicBlock *BB = PN->getParent(); | |||
| 1447 | if (!BB->canSplitPredecessors()) | |||
| 1448 | return false; | |||
| 1449 | // It's not impossible to split EHPad blocks, but if BlockColors already exist | |||
| 1450 | // it require updating BlockColors for all offspring blocks accordingly. By | |||
| 1451 | // skipping such corner case, we can make updating BlockColors after splitting | |||
| 1452 | // predecessor fairly simple. | |||
| 1453 | if (!SafetyInfo->getBlockColors().empty() && BB->getFirstNonPHI()->isEHPad()) | |||
| 1454 | return false; | |||
| 1455 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { | |||
| 1456 | BasicBlock *BBPred = *PI; | |||
| 1457 | if (isa<IndirectBrInst>(BBPred->getTerminator())) | |||
| 1458 | return false; | |||
| 1459 | } | |||
| 1460 | return true; | |||
| 1461 | } | |||
| 1462 | ||||
| 1463 | static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT, | |||
| 1464 | LoopInfo *LI, const Loop *CurLoop, | |||
| 1465 | LoopSafetyInfo *SafetyInfo, | |||
| 1466 | MemorySSAUpdater *MSSAU) { | |||
| 1467 | #ifndef NDEBUG | |||
| 1468 | SmallVector<BasicBlock *, 32> ExitBlocks; | |||
| 1469 | CurLoop->getUniqueExitBlocks(ExitBlocks); | |||
| 1470 | SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), | |||
| 1471 | ExitBlocks.end()); | |||
| 1472 | #endif | |||
| 1473 | BasicBlock *ExitBB = PN->getParent(); | |||
| 1474 | assert(ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block.")((ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block." ) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(ExitBB) && \"Expect the PHI is in an exit block.\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1474, __PRETTY_FUNCTION__)); | |||
| 1475 | ||||
| 1476 | // Split predecessors of the loop exit to make instructions in the loop are | |||
| 1477 | // exposed to exit blocks through trivially replaceable PHIs while keeping the | |||
| 1478 | // loop in the canonical form where each predecessor of each exit block should | |||
| 1479 | // be contained within the loop. For example, this will convert the loop below | |||
| 1480 | // from | |||
| 1481 | // | |||
| 1482 | // LB1: | |||
| 1483 | // %v1 = | |||
| 1484 | // br %LE, %LB2 | |||
| 1485 | // LB2: | |||
| 1486 | // %v2 = | |||
| 1487 | // br %LE, %LB1 | |||
| 1488 | // LE: | |||
| 1489 | // %p = phi [%v1, %LB1], [%v2, %LB2] <-- non-trivially replaceable | |||
| 1490 | // | |||
| 1491 | // to | |||
| 1492 | // | |||
| 1493 | // LB1: | |||
| 1494 | // %v1 = | |||
| 1495 | // br %LE.split, %LB2 | |||
| 1496 | // LB2: | |||
| 1497 | // %v2 = | |||
| 1498 | // br %LE.split2, %LB1 | |||
| 1499 | // LE.split: | |||
| 1500 | // %p1 = phi [%v1, %LB1] <-- trivially replaceable | |||
| 1501 | // br %LE | |||
| 1502 | // LE.split2: | |||
| 1503 | // %p2 = phi [%v2, %LB2] <-- trivially replaceable | |||
| 1504 | // br %LE | |||
| 1505 | // LE: | |||
| 1506 | // %p = phi [%p1, %LE.split], [%p2, %LE.split2] | |||
| 1507 | // | |||
| 1508 | const auto &BlockColors = SafetyInfo->getBlockColors(); | |||
| 1509 | SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB)); | |||
| 1510 | while (!PredBBs.empty()) { | |||
| 1511 | BasicBlock *PredBB = *PredBBs.begin(); | |||
| 1512 | assert(CurLoop->contains(PredBB) &&((CurLoop->contains(PredBB) && "Expect all predecessors are in the loop" ) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(PredBB) && \"Expect all predecessors are in the loop\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1513, __PRETTY_FUNCTION__)) | |||
| 1513 | "Expect all predecessors are in the loop")((CurLoop->contains(PredBB) && "Expect all predecessors are in the loop" ) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(PredBB) && \"Expect all predecessors are in the loop\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1513, __PRETTY_FUNCTION__)); | |||
| 1514 | if (PN->getBasicBlockIndex(PredBB) >= 0) { | |||
| 1515 | BasicBlock *NewPred = SplitBlockPredecessors( | |||
| 1516 | ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true); | |||
| 1517 | // Since we do not allow splitting EH-block with BlockColors in | |||
| 1518 | // canSplitPredecessors(), we can simply assign predecessor's color to | |||
| 1519 | // the new block. | |||
| 1520 | if (!BlockColors.empty()) | |||
| 1521 | // Grab a reference to the ColorVector to be inserted before getting the | |||
| 1522 | // reference to the vector we are copying because inserting the new | |||
| 1523 | // element in BlockColors might cause the map to be reallocated. | |||
| 1524 | SafetyInfo->copyColors(NewPred, PredBB); | |||
| 1525 | } | |||
| 1526 | PredBBs.remove(PredBB); | |||
| 1527 | } | |||
| 1528 | } | |||
| 1529 | ||||
| 1530 | /// When an instruction is found to only be used outside of the loop, this | |||
| 1531 | /// function moves it to the exit blocks and patches up SSA form as needed. | |||
| 1532 | /// This method is guaranteed to remove the original instruction from its | |||
| 1533 | /// position, and may either delete it or move it to outside of the loop. | |||
| 1534 | /// | |||
| 1535 | static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, | |||
| 1536 | const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, | |||
| 1537 | MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) { | |||
| 1538 | LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM sinking instruction: " << I << "\n"; } } while (false); | |||
| 1539 | ORE->emit([&]() { | |||
| 1540 | return OptimizationRemark(DEBUG_TYPE"licm", "InstSunk", &I) | |||
| 1541 | << "sinking " << ore::NV("Inst", &I); | |||
| 1542 | }); | |||
| 1543 | bool Changed = false; | |||
| 1544 | if (isa<LoadInst>(I)) | |||
| 1545 | ++NumMovedLoads; | |||
| 1546 | else if (isa<CallInst>(I)) | |||
| 1547 | ++NumMovedCalls; | |||
| 1548 | ++NumSunk; | |||
| 1549 | ||||
| 1550 | // Iterate over users to be ready for actual sinking. Replace users via | |||
| 1551 | // unreachable blocks with undef and make all user PHIs trivially replaceable. | |||
| 1552 | SmallPtrSet<Instruction *, 8> VisitedUsers; | |||
| 1553 | for (Value::user_iterator UI = I.user_begin(), UE = I.user_end(); UI != UE;) { | |||
| 1554 | auto *User = cast<Instruction>(*UI); | |||
| 1555 | Use &U = UI.getUse(); | |||
| 1556 | ++UI; | |||
| 1557 | ||||
| 1558 | if (VisitedUsers.count(User) || CurLoop->contains(User)) | |||
| 1559 | continue; | |||
| 1560 | ||||
| 1561 | if (!DT->isReachableFromEntry(User->getParent())) { | |||
| 1562 | U = UndefValue::get(I.getType()); | |||
| 1563 | Changed = true; | |||
| 1564 | continue; | |||
| 1565 | } | |||
| 1566 | ||||
| 1567 | // The user must be a PHI node. | |||
| 1568 | PHINode *PN = cast<PHINode>(User); | |||
| 1569 | ||||
| 1570 | // Surprisingly, instructions can be used outside of loops without any | |||
| 1571 | // exits. This can only happen in PHI nodes if the incoming block is | |||
| 1572 | // unreachable. | |||
| 1573 | BasicBlock *BB = PN->getIncomingBlock(U); | |||
| 1574 | if (!DT->isReachableFromEntry(BB)) { | |||
| 1575 | U = UndefValue::get(I.getType()); | |||
| 1576 | Changed = true; | |||
| 1577 | continue; | |||
| 1578 | } | |||
| 1579 | ||||
| 1580 | VisitedUsers.insert(PN); | |||
| 1581 | if (isTriviallyReplaceablePHI(*PN, I)) | |||
| 1582 | continue; | |||
| 1583 | ||||
| 1584 | if (!canSplitPredecessors(PN, SafetyInfo)) | |||
| 1585 | return Changed; | |||
| 1586 | ||||
| 1587 | // Split predecessors of the PHI so that we can make users trivially | |||
| 1588 | // replaceable. | |||
| 1589 | splitPredecessorsOfLoopExit(PN, DT, LI, CurLoop, SafetyInfo, MSSAU); | |||
| 1590 | ||||
| 1591 | // Should rebuild the iterators, as they may be invalidated by | |||
| 1592 | // splitPredecessorsOfLoopExit(). | |||
| 1593 | UI = I.user_begin(); | |||
| 1594 | UE = I.user_end(); | |||
| 1595 | } | |||
| 1596 | ||||
| 1597 | if (VisitedUsers.empty()) | |||
| 1598 | return Changed; | |||
| 1599 | ||||
| 1600 | #ifndef NDEBUG | |||
| 1601 | SmallVector<BasicBlock *, 32> ExitBlocks; | |||
| 1602 | CurLoop->getUniqueExitBlocks(ExitBlocks); | |||
| 1603 | SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), | |||
| 1604 | ExitBlocks.end()); | |||
| 1605 | #endif | |||
| 1606 | ||||
| 1607 | // Clones of this instruction. Don't create more than one per exit block! | |||
| 1608 | SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies; | |||
| 1609 | ||||
| 1610 | // If this instruction is only used outside of the loop, then all users are | |||
| 1611 | // PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of | |||
| 1612 | // the instruction. | |||
| 1613 | SmallSetVector<User*, 8> Users(I.user_begin(), I.user_end()); | |||
| 1614 | for (auto *UI : Users) { | |||
| 1615 | auto *User = cast<Instruction>(UI); | |||
| 1616 | ||||
| 1617 | if (CurLoop->contains(User)) | |||
| 1618 | continue; | |||
| 1619 | ||||
| 1620 | PHINode *PN = cast<PHINode>(User); | |||
| 1621 | assert(ExitBlockSet.count(PN->getParent()) &&((ExitBlockSet.count(PN->getParent()) && "The LCSSA PHI is not in an exit block!" ) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(PN->getParent()) && \"The LCSSA PHI is not in an exit block!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1622, __PRETTY_FUNCTION__)) | |||
| 1622 | "The LCSSA PHI is not in an exit block!")((ExitBlockSet.count(PN->getParent()) && "The LCSSA PHI is not in an exit block!" ) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(PN->getParent()) && \"The LCSSA PHI is not in an exit block!\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1622, __PRETTY_FUNCTION__)); | |||
| 1623 | // The PHI must be trivially replaceable. | |||
| 1624 | Instruction *New = sinkThroughTriviallyReplaceablePHI( | |||
| 1625 | PN, &I, LI, SunkCopies, SafetyInfo, CurLoop, MSSAU); | |||
| 1626 | PN->replaceAllUsesWith(New); | |||
| 1627 | eraseInstruction(*PN, *SafetyInfo, nullptr, nullptr); | |||
| 1628 | Changed = true; | |||
| 1629 | } | |||
| 1630 | return Changed; | |||
| 1631 | } | |||
| 1632 | ||||
| 1633 | /// When an instruction is found to only use loop invariant operands that | |||
| 1634 | /// is safe to hoist, this instruction is called to do the dirty work. | |||
| 1635 | /// | |||
| 1636 | static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, | |||
| 1637 | BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, | |||
| 1638 | MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) { | |||
| 1639 | LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getName() << ": " << Ido { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM hoisting to " << Dest ->getName() << ": " << I << "\n"; } } while (false) | |||
| 1640 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM hoisting to " << Dest ->getName() << ": " << I << "\n"; } } while (false); | |||
| 1641 | ORE->emit([&]() { | |||
| 1642 | return OptimizationRemark(DEBUG_TYPE"licm", "Hoisted", &I) << "hoisting " | |||
| 1643 | << ore::NV("Inst", &I); | |||
| 1644 | }); | |||
| 1645 | ||||
| 1646 | // Metadata can be dependent on conditions we are hoisting above. | |||
| 1647 | // Conservatively strip all metadata on the instruction unless we were | |||
| 1648 | // guaranteed to execute I if we entered the loop, in which case the metadata | |||
| 1649 | // is valid in the loop preheader. | |||
| 1650 | if (I.hasMetadataOtherThanDebugLoc() && | |||
| 1651 | // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning | |||
| 1652 | // time in isGuaranteedToExecute if we don't actually have anything to | |||
| 1653 | // drop. It is a compile time optimization, not required for correctness. | |||
| 1654 | !SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop)) | |||
| 1655 | I.dropUnknownNonDebugMetadata(); | |||
| 1656 | ||||
| 1657 | if (isa<PHINode>(I)) | |||
| 1658 | // Move the new node to the end of the phi list in the destination block. | |||
| 1659 | moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU); | |||
| 1660 | else | |||
| 1661 | // Move the new node to the destination block, before its terminator. | |||
| 1662 | moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU); | |||
| 1663 | ||||
| 1664 | // Apply line 0 debug locations when we are moving instructions to different | |||
| 1665 | // basic blocks because we want to avoid jumpy line tables. | |||
| 1666 | if (const DebugLoc &DL = I.getDebugLoc()) | |||
| 1667 | I.setDebugLoc(DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt())); | |||
| 1668 | ||||
| 1669 | if (isa<LoadInst>(I)) | |||
| 1670 | ++NumMovedLoads; | |||
| 1671 | else if (isa<CallInst>(I)) | |||
| 1672 | ++NumMovedCalls; | |||
| 1673 | ++NumHoisted; | |||
| 1674 | } | |||
| 1675 | ||||
| 1676 | /// Only sink or hoist an instruction if it is not a trapping instruction, | |||
| 1677 | /// or if the instruction is known not to trap when moved to the preheader. | |||
| 1678 | /// or if it is a trapping instruction and is guaranteed to execute. | |||
| 1679 | static bool isSafeToExecuteUnconditionally(Instruction &Inst, | |||
| 1680 | const DominatorTree *DT, | |||
| 1681 | const Loop *CurLoop, | |||
| 1682 | const LoopSafetyInfo *SafetyInfo, | |||
| 1683 | OptimizationRemarkEmitter *ORE, | |||
| 1684 | const Instruction *CtxI) { | |||
| 1685 | if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT)) | |||
| 1686 | return true; | |||
| 1687 | ||||
| 1688 | bool GuaranteedToExecute = | |||
| 1689 | SafetyInfo->isGuaranteedToExecute(Inst, DT, CurLoop); | |||
| 1690 | ||||
| 1691 | if (!GuaranteedToExecute) { | |||
| 1692 | auto *LI = dyn_cast<LoadInst>(&Inst); | |||
| 1693 | if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand())) | |||
| 1694 | ORE->emit([&]() { | |||
| 1695 | return OptimizationRemarkMissed( | |||
| 1696 | DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressCondExecuted", LI) | |||
| 1697 | << "failed to hoist load with loop-invariant address " | |||
| 1698 | "because load is conditionally executed"; | |||
| 1699 | }); | |||
| 1700 | } | |||
| 1701 | ||||
| 1702 | return GuaranteedToExecute; | |||
| 1703 | } | |||
| 1704 | ||||
| 1705 | namespace { | |||
| 1706 | class LoopPromoter : public LoadAndStorePromoter { | |||
| 1707 | Value *SomePtr; // Designated pointer to store to. | |||
| 1708 | const SmallSetVector<Value *, 8> &PointerMustAliases; | |||
| 1709 | SmallVectorImpl<BasicBlock *> &LoopExitBlocks; | |||
| 1710 | SmallVectorImpl<Instruction *> &LoopInsertPts; | |||
| 1711 | SmallVectorImpl<MemoryAccess *> &MSSAInsertPts; | |||
| 1712 | PredIteratorCache &PredCache; | |||
| 1713 | AliasSetTracker &AST; | |||
| 1714 | MemorySSAUpdater *MSSAU; | |||
| 1715 | LoopInfo &LI; | |||
| 1716 | DebugLoc DL; | |||
| 1717 | int Alignment; | |||
| 1718 | bool UnorderedAtomic; | |||
| 1719 | AAMDNodes AATags; | |||
| 1720 | ICFLoopSafetyInfo &SafetyInfo; | |||
| 1721 | ||||
| 1722 | Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const { | |||
| 1723 | if (Instruction *I = dyn_cast<Instruction>(V)) | |||
| 1724 | if (Loop *L = LI.getLoopFor(I->getParent())) | |||
| 1725 | if (!L->contains(BB)) { | |||
| 1726 | // We need to create an LCSSA PHI node for the incoming value and | |||
| 1727 | // store that. | |||
| 1728 | PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB), | |||
| 1729 | I->getName() + ".lcssa", &BB->front()); | |||
| 1730 | for (BasicBlock *Pred : PredCache.get(BB)) | |||
| 1731 | PN->addIncoming(I, Pred); | |||
| 1732 | return PN; | |||
| 1733 | } | |||
| 1734 | return V; | |||
| 1735 | } | |||
| 1736 | ||||
| 1737 | public: | |||
| 1738 | LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S, | |||
| 1739 | const SmallSetVector<Value *, 8> &PMA, | |||
| 1740 | SmallVectorImpl<BasicBlock *> &LEB, | |||
| 1741 | SmallVectorImpl<Instruction *> &LIP, | |||
| 1742 | SmallVectorImpl<MemoryAccess *> &MSSAIP, PredIteratorCache &PIC, | |||
| 1743 | AliasSetTracker &ast, MemorySSAUpdater *MSSAU, LoopInfo &li, | |||
| 1744 | DebugLoc dl, int alignment, bool UnorderedAtomic, | |||
| 1745 | const AAMDNodes &AATags, ICFLoopSafetyInfo &SafetyInfo) | |||
| 1746 | : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA), | |||
| 1747 | LoopExitBlocks(LEB), LoopInsertPts(LIP), MSSAInsertPts(MSSAIP), | |||
| 1748 | PredCache(PIC), AST(ast), MSSAU(MSSAU), LI(li), DL(std::move(dl)), | |||
| 1749 | Alignment(alignment), UnorderedAtomic(UnorderedAtomic), AATags(AATags), | |||
| 1750 | SafetyInfo(SafetyInfo) {} | |||
| 1751 | ||||
| 1752 | bool isInstInList(Instruction *I, | |||
| 1753 | const SmallVectorImpl<Instruction *> &) const override { | |||
| 1754 | Value *Ptr; | |||
| 1755 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) | |||
| 1756 | Ptr = LI->getOperand(0); | |||
| 1757 | else | |||
| 1758 | Ptr = cast<StoreInst>(I)->getPointerOperand(); | |||
| 1759 | return PointerMustAliases.count(Ptr); | |||
| 1760 | } | |||
| 1761 | ||||
| 1762 | void doExtraRewritesBeforeFinalDeletion() override { | |||
| 1763 | // Insert stores after in the loop exit blocks. Each exit block gets a | |||
| 1764 | // store of the live-out values that feed them. Since we've already told | |||
| 1765 | // the SSA updater about the defs in the loop and the preheader | |||
| 1766 | // definition, it is all set and we can start using it. | |||
| 1767 | for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) { | |||
| 1768 | BasicBlock *ExitBlock = LoopExitBlocks[i]; | |||
| 1769 | Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); | |||
| 1770 | LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock); | |||
| 1771 | Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock); | |||
| 1772 | Instruction *InsertPos = LoopInsertPts[i]; | |||
| 1773 | StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos); | |||
| 1774 | if (UnorderedAtomic) | |||
| 1775 | NewSI->setOrdering(AtomicOrdering::Unordered); | |||
| 1776 | NewSI->setAlignment(Alignment); | |||
| 1777 | NewSI->setDebugLoc(DL); | |||
| 1778 | if (AATags) | |||
| 1779 | NewSI->setAAMetadata(AATags); | |||
| 1780 | ||||
| 1781 | if (MSSAU) { | |||
| 1782 | MemoryAccess *MSSAInsertPoint = MSSAInsertPts[i]; | |||
| 1783 | MemoryAccess *NewMemAcc; | |||
| 1784 | if (!MSSAInsertPoint) { | |||
| 1785 | NewMemAcc = MSSAU->createMemoryAccessInBB( | |||
| 1786 | NewSI, nullptr, NewSI->getParent(), MemorySSA::Beginning); | |||
| 1787 | } else { | |||
| 1788 | NewMemAcc = | |||
| 1789 | MSSAU->createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint); | |||
| 1790 | } | |||
| 1791 | MSSAInsertPts[i] = NewMemAcc; | |||
| 1792 | MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true); | |||
| 1793 | // FIXME: true for safety, false may still be correct. | |||
| 1794 | } | |||
| 1795 | } | |||
| 1796 | } | |||
| 1797 | ||||
| 1798 | void replaceLoadWithValue(LoadInst *LI, Value *V) const override { | |||
| 1799 | // Update alias analysis. | |||
| 1800 | AST.copyValue(LI, V); | |||
| 1801 | } | |||
| 1802 | void instructionDeleted(Instruction *I) const override { | |||
| 1803 | SafetyInfo.removeInstruction(I); | |||
| 1804 | AST.deleteValue(I); | |||
| 1805 | if (MSSAU) | |||
| 1806 | MSSAU->removeMemoryAccess(I); | |||
| 1807 | } | |||
| 1808 | }; | |||
| 1809 | ||||
| 1810 | ||||
| 1811 | /// Return true iff we can prove that a caller of this function can not inspect | |||
| 1812 | /// the contents of the provided object in a well defined program. | |||
| 1813 | bool isKnownNonEscaping(Value *Object, const TargetLibraryInfo *TLI) { | |||
| 1814 | if (isa<AllocaInst>(Object)) | |||
| 1815 | // Since the alloca goes out of scope, we know the caller can't retain a | |||
| 1816 | // reference to it and be well defined. Thus, we don't need to check for | |||
| 1817 | // capture. | |||
| 1818 | return true; | |||
| 1819 | ||||
| 1820 | // For all other objects we need to know that the caller can't possibly | |||
| 1821 | // have gotten a reference to the object. There are two components of | |||
| 1822 | // that: | |||
| 1823 | // 1) Object can't be escaped by this function. This is what | |||
| 1824 | // PointerMayBeCaptured checks. | |||
| 1825 | // 2) Object can't have been captured at definition site. For this, we | |||
| 1826 | // need to know the return value is noalias. At the moment, we use a | |||
| 1827 | // weaker condition and handle only AllocLikeFunctions (which are | |||
| 1828 | // known to be noalias). TODO | |||
| 1829 | return isAllocLikeFn(Object, TLI) && | |||
| 1830 | !PointerMayBeCaptured(Object, true, true); | |||
| 1831 | } | |||
| 1832 | ||||
| 1833 | } // namespace | |||
| 1834 | ||||
| 1835 | /// Try to promote memory values to scalars by sinking stores out of the | |||
| 1836 | /// loop and moving loads to before the loop. We do this by looping over | |||
| 1837 | /// the stores in the loop, looking for stores to Must pointers which are | |||
| 1838 | /// loop invariant. | |||
| 1839 | /// | |||
| 1840 | bool llvm::promoteLoopAccessesToScalars( | |||
| 1841 | const SmallSetVector<Value *, 8> &PointerMustAliases, | |||
| 1842 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | |||
| 1843 | SmallVectorImpl<Instruction *> &InsertPts, | |||
| 1844 | SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC, | |||
| 1845 | LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI, | |||
| 1846 | Loop *CurLoop, AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, | |||
| 1847 | ICFLoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE) { | |||
| 1848 | // Verify inputs. | |||
| 1849 | assert(LI != nullptr && DT != nullptr && CurLoop != nullptr &&((LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && "Unexpected Input to promoteLoopAccessesToScalars" ) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1851, __PRETTY_FUNCTION__)) | |||
| 1850 | CurAST != nullptr && SafetyInfo != nullptr &&((LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && "Unexpected Input to promoteLoopAccessesToScalars" ) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1851, __PRETTY_FUNCTION__)) | |||
| 1851 | "Unexpected Input to promoteLoopAccessesToScalars")((LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && "Unexpected Input to promoteLoopAccessesToScalars" ) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 1851, __PRETTY_FUNCTION__)); | |||
| 1852 | ||||
| 1853 | Value *SomePtr = *PointerMustAliases.begin(); | |||
| 1854 | BasicBlock *Preheader = CurLoop->getLoopPreheader(); | |||
| 1855 | ||||
| 1856 | // It is not safe to promote a load/store from the loop if the load/store is | |||
| 1857 | // conditional. For example, turning: | |||
| 1858 | // | |||
| 1859 | // for () { if (c) *P += 1; } | |||
| 1860 | // | |||
| 1861 | // into: | |||
| 1862 | // | |||
| 1863 | // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; | |||
| 1864 | // | |||
| 1865 | // is not safe, because *P may only be valid to access if 'c' is true. | |||
| 1866 | // | |||
| 1867 | // The safety property divides into two parts: | |||
| 1868 | // p1) The memory may not be dereferenceable on entry to the loop. In this | |||
| 1869 | // case, we can't insert the required load in the preheader. | |||
| 1870 | // p2) The memory model does not allow us to insert a store along any dynamic | |||
| 1871 | // path which did not originally have one. | |||
| 1872 | // | |||
| 1873 | // If at least one store is guaranteed to execute, both properties are | |||
| 1874 | // satisfied, and promotion is legal. | |||
| 1875 | // | |||
| 1876 | // This, however, is not a necessary condition. Even if no store/load is | |||
| 1877 | // guaranteed to execute, we can still establish these properties. | |||
| 1878 | // We can establish (p1) by proving that hoisting the load into the preheader | |||
| 1879 | // is safe (i.e. proving dereferenceability on all paths through the loop). We | |||
| 1880 | // can use any access within the alias set to prove dereferenceability, | |||
| 1881 | // since they're all must alias. | |||
| 1882 | // | |||
| 1883 | // There are two ways establish (p2): | |||
| 1884 | // a) Prove the location is thread-local. In this case the memory model | |||
| 1885 | // requirement does not apply, and stores are safe to insert. | |||
| 1886 | // b) Prove a store dominates every exit block. In this case, if an exit | |||
| 1887 | // blocks is reached, the original dynamic path would have taken us through | |||
| 1888 | // the store, so inserting a store into the exit block is safe. Note that this | |||
| 1889 | // is different from the store being guaranteed to execute. For instance, | |||
| 1890 | // if an exception is thrown on the first iteration of the loop, the original | |||
| 1891 | // store is never executed, but the exit blocks are not executed either. | |||
| 1892 | ||||
| 1893 | bool DereferenceableInPH = false; | |||
| 1894 | bool SafeToInsertStore = false; | |||
| 1895 | ||||
| 1896 | SmallVector<Instruction *, 64> LoopUses; | |||
| 1897 | ||||
| 1898 | // We start with an alignment of one and try to find instructions that allow | |||
| 1899 | // us to prove better alignment. | |||
| 1900 | unsigned Alignment = 1; | |||
| 1901 | // Keep track of which types of access we see | |||
| 1902 | bool SawUnorderedAtomic = false; | |||
| 1903 | bool SawNotAtomic = false; | |||
| 1904 | AAMDNodes AATags; | |||
| 1905 | ||||
| 1906 | const DataLayout &MDL = Preheader->getModule()->getDataLayout(); | |||
| 1907 | ||||
| 1908 | bool IsKnownThreadLocalObject = false; | |||
| 1909 | if (SafetyInfo->anyBlockMayThrow()) { | |||
| 1910 | // If a loop can throw, we have to insert a store along each unwind edge. | |||
| 1911 | // That said, we can't actually make the unwind edge explicit. Therefore, | |||
| 1912 | // we have to prove that the store is dead along the unwind edge. We do | |||
| 1913 | // this by proving that the caller can't have a reference to the object | |||
| 1914 | // after return and thus can't possibly load from the object. | |||
| 1915 | Value *Object = GetUnderlyingObject(SomePtr, MDL); | |||
| 1916 | if (!isKnownNonEscaping(Object, TLI)) | |||
| 1917 | return false; | |||
| 1918 | // Subtlety: Alloca's aren't visible to callers, but *are* potentially | |||
| 1919 | // visible to other threads if captured and used during their lifetimes. | |||
| 1920 | IsKnownThreadLocalObject = !isa<AllocaInst>(Object); | |||
| 1921 | } | |||
| 1922 | ||||
| 1923 | // Check that all of the pointers in the alias set have the same type. We | |||
| 1924 | // cannot (yet) promote a memory location that is loaded and stored in | |||
| 1925 | // different sizes. While we are at it, collect alignment and AA info. | |||
| 1926 | for (Value *ASIV : PointerMustAliases) { | |||
| 1927 | // Check that all of the pointers in the alias set have the same type. We | |||
| 1928 | // cannot (yet) promote a memory location that is loaded and stored in | |||
| 1929 | // different sizes. | |||
| 1930 | if (SomePtr->getType() != ASIV->getType()) | |||
| 1931 | return false; | |||
| 1932 | ||||
| 1933 | for (User *U : ASIV->users()) { | |||
| 1934 | // Ignore instructions that are outside the loop. | |||
| 1935 | Instruction *UI = dyn_cast<Instruction>(U); | |||
| 1936 | if (!UI || !CurLoop->contains(UI)) | |||
| 1937 | continue; | |||
| 1938 | ||||
| 1939 | // If there is an non-load/store instruction in the loop, we can't promote | |||
| 1940 | // it. | |||
| 1941 | if (LoadInst *Load = dyn_cast<LoadInst>(UI)) { | |||
| 1942 | if (!Load->isUnordered()) | |||
| 1943 | return false; | |||
| 1944 | ||||
| 1945 | SawUnorderedAtomic |= Load->isAtomic(); | |||
| 1946 | SawNotAtomic |= !Load->isAtomic(); | |||
| 1947 | ||||
| 1948 | unsigned InstAlignment = Load->getAlignment(); | |||
| 1949 | if (!InstAlignment) | |||
| 1950 | InstAlignment = | |||
| 1951 | MDL.getABITypeAlignment(Load->getType()); | |||
| 1952 | ||||
| 1953 | // Note that proving a load safe to speculate requires proving | |||
| 1954 | // sufficient alignment at the target location. Proving it guaranteed | |||
| 1955 | // to execute does as well. Thus we can increase our guaranteed | |||
| 1956 | // alignment as well. | |||
| 1957 | if (!DereferenceableInPH || (InstAlignment > Alignment)) | |||
| 1958 | if (isSafeToExecuteUnconditionally(*Load, DT, CurLoop, SafetyInfo, | |||
| 1959 | ORE, Preheader->getTerminator())) { | |||
| 1960 | DereferenceableInPH = true; | |||
| 1961 | Alignment = std::max(Alignment, InstAlignment); | |||
| 1962 | } | |||
| 1963 | } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) { | |||
| 1964 | // Stores *of* the pointer are not interesting, only stores *to* the | |||
| 1965 | // pointer. | |||
| 1966 | if (UI->getOperand(1) != ASIV) | |||
| 1967 | continue; | |||
| 1968 | if (!Store->isUnordered()) | |||
| 1969 | return false; | |||
| 1970 | ||||
| 1971 | SawUnorderedAtomic |= Store->isAtomic(); | |||
| 1972 | SawNotAtomic |= !Store->isAtomic(); | |||
| 1973 | ||||
| 1974 | // If the store is guaranteed to execute, both properties are satisfied. | |||
| 1975 | // We may want to check if a store is guaranteed to execute even if we | |||
| 1976 | // already know that promotion is safe, since it may have higher | |||
| 1977 | // alignment than any other guaranteed stores, in which case we can | |||
| 1978 | // raise the alignment on the promoted store. | |||
| 1979 | unsigned InstAlignment = Store->getAlignment(); | |||
| 1980 | if (!InstAlignment) | |||
| 1981 | InstAlignment = | |||
| 1982 | MDL.getABITypeAlignment(Store->getValueOperand()->getType()); | |||
| 1983 | ||||
| 1984 | if (!DereferenceableInPH || !SafeToInsertStore || | |||
| 1985 | (InstAlignment > Alignment)) { | |||
| 1986 | if (SafetyInfo->isGuaranteedToExecute(*UI, DT, CurLoop)) { | |||
| 1987 | DereferenceableInPH = true; | |||
| 1988 | SafeToInsertStore = true; | |||
| 1989 | Alignment = std::max(Alignment, InstAlignment); | |||
| 1990 | } | |||
| 1991 | } | |||
| 1992 | ||||
| 1993 | // If a store dominates all exit blocks, it is safe to sink. | |||
| 1994 | // As explained above, if an exit block was executed, a dominating | |||
| 1995 | // store must have been executed at least once, so we are not | |||
| 1996 | // introducing stores on paths that did not have them. | |||
| 1997 | // Note that this only looks at explicit exit blocks. If we ever | |||
| 1998 | // start sinking stores into unwind edges (see above), this will break. | |||
| 1999 | if (!SafeToInsertStore) | |||
| 2000 | SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) { | |||
| 2001 | return DT->dominates(Store->getParent(), Exit); | |||
| 2002 | }); | |||
| 2003 | ||||
| 2004 | // If the store is not guaranteed to execute, we may still get | |||
| 2005 | // deref info through it. | |||
| 2006 | if (!DereferenceableInPH) { | |||
| 2007 | DereferenceableInPH = isDereferenceableAndAlignedPointer( | |||
| 2008 | Store->getPointerOperand(), Store->getAlignment(), MDL, | |||
| 2009 | Preheader->getTerminator(), DT); | |||
| 2010 | } | |||
| 2011 | } else | |||
| 2012 | return false; // Not a load or store. | |||
| 2013 | ||||
| 2014 | // Merge the AA tags. | |||
| 2015 | if (LoopUses.empty()) { | |||
| 2016 | // On the first load/store, just take its AA tags. | |||
| 2017 | UI->getAAMetadata(AATags); | |||
| 2018 | } else if (AATags) { | |||
| 2019 | UI->getAAMetadata(AATags, /* Merge = */ true); | |||
| 2020 | } | |||
| 2021 | ||||
| 2022 | LoopUses.push_back(UI); | |||
| 2023 | } | |||
| 2024 | } | |||
| 2025 | ||||
| 2026 | // If we found both an unordered atomic instruction and a non-atomic memory | |||
| 2027 | // access, bail. We can't blindly promote non-atomic to atomic since we | |||
| 2028 | // might not be able to lower the result. We can't downgrade since that | |||
| 2029 | // would violate memory model. Also, align 0 is an error for atomics. | |||
| 2030 | if (SawUnorderedAtomic && SawNotAtomic) | |||
| 2031 | return false; | |||
| 2032 | ||||
| 2033 | // If we're inserting an atomic load in the preheader, we must be able to | |||
| 2034 | // lower it. We're only guaranteed to be able to lower naturally aligned | |||
| 2035 | // atomics. | |||
| 2036 | auto *SomePtrElemType = SomePtr->getType()->getPointerElementType(); | |||
| 2037 | if (SawUnorderedAtomic && | |||
| 2038 | Alignment < MDL.getTypeStoreSize(SomePtrElemType)) | |||
| 2039 | return false; | |||
| 2040 | ||||
| 2041 | // If we couldn't prove we can hoist the load, bail. | |||
| 2042 | if (!DereferenceableInPH) | |||
| 2043 | return false; | |||
| 2044 | ||||
| 2045 | // We know we can hoist the load, but don't have a guaranteed store. | |||
| 2046 | // Check whether the location is thread-local. If it is, then we can insert | |||
| 2047 | // stores along paths which originally didn't have them without violating the | |||
| 2048 | // memory model. | |||
| 2049 | if (!SafeToInsertStore) { | |||
| 2050 | if (IsKnownThreadLocalObject) | |||
| 2051 | SafeToInsertStore = true; | |||
| 2052 | else { | |||
| 2053 | Value *Object = GetUnderlyingObject(SomePtr, MDL); | |||
| 2054 | SafeToInsertStore = | |||
| 2055 | (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) && | |||
| 2056 | !PointerMayBeCaptured(Object, true, true); | |||
| 2057 | } | |||
| 2058 | } | |||
| 2059 | ||||
| 2060 | // If we've still failed to prove we can sink the store, give up. | |||
| 2061 | if (!SafeToInsertStore) | |||
| 2062 | return false; | |||
| 2063 | ||||
| 2064 | // Otherwise, this is safe to promote, lets do it! | |||
| 2065 | LLVM_DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtrdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtr << '\n'; } } while (false) | |||
| 2066 | << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtr << '\n'; } } while (false); | |||
| 2067 | ORE->emit([&]() { | |||
| 2068 | return OptimizationRemark(DEBUG_TYPE"licm", "PromoteLoopAccessesToScalar", | |||
| 2069 | LoopUses[0]) | |||
| 2070 | << "Moving accesses to memory location out of the loop"; | |||
| 2071 | }); | |||
| 2072 | ++NumPromoted; | |||
| 2073 | ||||
| 2074 | // Grab a debug location for the inserted loads/stores; given that the | |||
| 2075 | // inserted loads/stores have little relation to the original loads/stores, | |||
| 2076 | // this code just arbitrarily picks a location from one, since any debug | |||
| 2077 | // location is better than none. | |||
| 2078 | DebugLoc DL = LoopUses[0]->getDebugLoc(); | |||
| 2079 | ||||
| 2080 | // We use the SSAUpdater interface to insert phi nodes as required. | |||
| 2081 | SmallVector<PHINode *, 16> NewPHIs; | |||
| 2082 | SSAUpdater SSA(&NewPHIs); | |||
| 2083 | LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks, | |||
| 2084 | InsertPts, MSSAInsertPts, PIC, *CurAST, MSSAU, *LI, DL, | |||
| 2085 | Alignment, SawUnorderedAtomic, AATags, *SafetyInfo); | |||
| 2086 | ||||
| 2087 | // Set up the preheader to have a definition of the value. It is the live-out | |||
| 2088 | // value from the preheader that uses in the loop will use. | |||
| 2089 | LoadInst *PreheaderLoad = new LoadInst( | |||
| 2090 | SomePtr->getType()->getPointerElementType(), SomePtr, | |||
| 2091 | SomePtr->getName() + ".promoted", Preheader->getTerminator()); | |||
| 2092 | if (SawUnorderedAtomic) | |||
| 2093 | PreheaderLoad->setOrdering(AtomicOrdering::Unordered); | |||
| 2094 | PreheaderLoad->setAlignment(Alignment); | |||
| 2095 | PreheaderLoad->setDebugLoc(DL); | |||
| 2096 | if (AATags) | |||
| 2097 | PreheaderLoad->setAAMetadata(AATags); | |||
| 2098 | SSA.AddAvailableValue(Preheader, PreheaderLoad); | |||
| 2099 | ||||
| 2100 | MemoryAccess *PreheaderLoadMemoryAccess; | |||
| 2101 | if (MSSAU) { | |||
| 2102 | PreheaderLoadMemoryAccess = MSSAU->createMemoryAccessInBB( | |||
| 2103 | PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End); | |||
| 2104 | MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess); | |||
| 2105 | MSSAU->insertUse(NewMemUse); | |||
| 2106 | } | |||
| 2107 | ||||
| 2108 | // Rewrite all the loads in the loop and remember all the definitions from | |||
| 2109 | // stores in the loop. | |||
| 2110 | Promoter.run(LoopUses); | |||
| 2111 | ||||
| 2112 | if (MSSAU && VerifyMemorySSA) | |||
| 2113 | MSSAU->getMemorySSA()->verifyMemorySSA(); | |||
| 2114 | // If the SSAUpdater didn't use the load in the preheader, just zap it now. | |||
| 2115 | if (PreheaderLoad->use_empty()) | |||
| 2116 | eraseInstruction(*PreheaderLoad, *SafetyInfo, CurAST, MSSAU); | |||
| 2117 | ||||
| 2118 | return true; | |||
| 2119 | } | |||
| 2120 | ||||
| 2121 | /// Returns an owning pointer to an alias set which incorporates aliasing info | |||
| 2122 | /// from L and all subloops of L. | |||
| 2123 | /// FIXME: In new pass manager, there is no helper function to handle loop | |||
| 2124 | /// analysis such as cloneBasicBlockAnalysis, so the AST needs to be recomputed | |||
| 2125 | /// from scratch for every loop. Hook up with the helper functions when | |||
| 2126 | /// available in the new pass manager to avoid redundant computation. | |||
| 2127 | std::unique_ptr<AliasSetTracker> | |||
| 2128 | LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI, | |||
| 2129 | AliasAnalysis *AA) { | |||
| 2130 | std::unique_ptr<AliasSetTracker> CurAST; | |||
| 2131 | SmallVector<Loop *, 4> RecomputeLoops; | |||
| 2132 | for (Loop *InnerL : L->getSubLoops()) { | |||
| 2133 | auto MapI = LoopToAliasSetMap.find(InnerL); | |||
| 2134 | // If the AST for this inner loop is missing it may have been merged into | |||
| 2135 | // some other loop's AST and then that loop unrolled, and so we need to | |||
| 2136 | // recompute it. | |||
| 2137 | if (MapI == LoopToAliasSetMap.end()) { | |||
| 2138 | RecomputeLoops.push_back(InnerL); | |||
| 2139 | continue; | |||
| 2140 | } | |||
| 2141 | std::unique_ptr<AliasSetTracker> InnerAST = std::move(MapI->second); | |||
| 2142 | ||||
| 2143 | if (CurAST) { | |||
| 2144 | // What if InnerLoop was modified by other passes ? | |||
| 2145 | // Once we've incorporated the inner loop's AST into ours, we don't need | |||
| 2146 | // the subloop's anymore. | |||
| 2147 | CurAST->add(*InnerAST); | |||
| 2148 | } else { | |||
| 2149 | CurAST = std::move(InnerAST); | |||
| 2150 | } | |||
| 2151 | LoopToAliasSetMap.erase(MapI); | |||
| 2152 | } | |||
| 2153 | if (!CurAST) | |||
| 2154 | CurAST = make_unique<AliasSetTracker>(*AA); | |||
| 2155 | ||||
| 2156 | // Add everything from the sub loops that are no longer directly available. | |||
| 2157 | for (Loop *InnerL : RecomputeLoops) | |||
| 2158 | for (BasicBlock *BB : InnerL->blocks()) | |||
| 2159 | CurAST->add(*BB); | |||
| 2160 | ||||
| 2161 | // And merge in this loop (without anything from inner loops). | |||
| 2162 | for (BasicBlock *BB : L->blocks()) | |||
| 2163 | if (LI->getLoopFor(BB) == L) | |||
| 2164 | CurAST->add(*BB); | |||
| 2165 | ||||
| 2166 | return CurAST; | |||
| 2167 | } | |||
| 2168 | ||||
| 2169 | std::unique_ptr<AliasSetTracker> | |||
| 2170 | LoopInvariantCodeMotion::collectAliasInfoForLoopWithMSSA( | |||
| 2171 | Loop *L, AliasAnalysis *AA, MemorySSAUpdater *MSSAU) { | |||
| 2172 | auto *MSSA = MSSAU->getMemorySSA(); | |||
| 2173 | auto CurAST = make_unique<AliasSetTracker>(*AA, MSSA, L); | |||
| 2174 | CurAST->addAllInstructionsInLoopUsingMSSA(); | |||
| 2175 | return CurAST; | |||
| 2176 | } | |||
| 2177 | ||||
| 2178 | /// Simple analysis hook. Clone alias set info. | |||
| 2179 | /// | |||
| 2180 | void LegacyLICMPass::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, | |||
| 2181 | Loop *L) { | |||
| 2182 | auto ASTIt = LICM.getLoopToAliasSetMap().find(L); | |||
| 2183 | if (ASTIt == LICM.getLoopToAliasSetMap().end()) | |||
| 2184 | return; | |||
| 2185 | ||||
| 2186 | ASTIt->second->copyValue(From, To); | |||
| 2187 | } | |||
| 2188 | ||||
| 2189 | /// Simple Analysis hook. Delete value V from alias set | |||
| 2190 | /// | |||
| 2191 | void LegacyLICMPass::deleteAnalysisValue(Value *V, Loop *L) { | |||
| 2192 | auto ASTIt = LICM.getLoopToAliasSetMap().find(L); | |||
| 2193 | if (ASTIt == LICM.getLoopToAliasSetMap().end()) | |||
| 2194 | return; | |||
| 2195 | ||||
| 2196 | ASTIt->second->deleteValue(V); | |||
| 2197 | } | |||
| 2198 | ||||
| 2199 | /// Simple Analysis hook. Delete value L from alias set map. | |||
| 2200 | /// | |||
| 2201 | void LegacyLICMPass::deleteAnalysisLoop(Loop *L) { | |||
| 2202 | if (!LICM.getLoopToAliasSetMap().count(L)) | |||
| 2203 | return; | |||
| 2204 | ||||
| 2205 | LICM.getLoopToAliasSetMap().erase(L); | |||
| 2206 | } | |||
| 2207 | ||||
| 2208 | static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, | |||
| 2209 | AliasSetTracker *CurAST, Loop *CurLoop, | |||
| 2210 | AliasAnalysis *AA) { | |||
| 2211 | // First check to see if any of the basic blocks in CurLoop invalidate *V. | |||
| 2212 | bool isInvalidatedAccordingToAST = CurAST->getAliasSetFor(MemLoc).isMod(); | |||
| 2213 | ||||
| 2214 | if (!isInvalidatedAccordingToAST || !LICMN2Theshold) | |||
| 2215 | return isInvalidatedAccordingToAST; | |||
| 2216 | ||||
| 2217 | // Check with a diagnostic analysis if we can refine the information above. | |||
| 2218 | // This is to identify the limitations of using the AST. | |||
| 2219 | // The alias set mechanism used by LICM has a major weakness in that it | |||
| 2220 | // combines all things which may alias into a single set *before* asking | |||
| 2221 | // modref questions. As a result, a single readonly call within a loop will | |||
| 2222 | // collapse all loads and stores into a single alias set and report | |||
| 2223 | // invalidation if the loop contains any store. For example, readonly calls | |||
| 2224 | // with deopt states have this form and create a general alias set with all | |||
| 2225 | // loads and stores. In order to get any LICM in loops containing possible | |||
| 2226 | // deopt states we need a more precise invalidation of checking the mod ref | |||
| 2227 | // info of each instruction within the loop and LI. This has a complexity of | |||
| 2228 | // O(N^2), so currently, it is used only as a diagnostic tool since the | |||
| 2229 | // default value of LICMN2Threshold is zero. | |||
| 2230 | ||||
| 2231 | // Don't look at nested loops. | |||
| 2232 | if (CurLoop->begin() != CurLoop->end()) | |||
| 2233 | return true; | |||
| 2234 | ||||
| 2235 | int N = 0; | |||
| 2236 | for (BasicBlock *BB : CurLoop->getBlocks()) | |||
| 2237 | for (Instruction &I : *BB) { | |||
| 2238 | if (N >= LICMN2Theshold) { | |||
| 2239 | LLVM_DEBUG(dbgs() << "Alasing N2 threshold exhausted for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "Alasing N2 threshold exhausted for " << *(MemLoc.Ptr) << "\n"; } } while (false) | |||
| 2240 | << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "Alasing N2 threshold exhausted for " << *(MemLoc.Ptr) << "\n"; } } while (false); | |||
| 2241 | return true; | |||
| 2242 | } | |||
| 2243 | N++; | |||
| 2244 | auto Res = AA->getModRefInfo(&I, MemLoc); | |||
| 2245 | if (isModSet(Res)) { | |||
| 2246 | LLVM_DEBUG(dbgs() << "Aliasing failed on " << I << " for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "Aliasing failed on " << I << " for " << *(MemLoc.Ptr) << "\n"; } } while (false ) | |||
| 2247 | << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "Aliasing failed on " << I << " for " << *(MemLoc.Ptr) << "\n"; } } while (false ); | |||
| 2248 | return true; | |||
| 2249 | } | |||
| 2250 | } | |||
| 2251 | LLVM_DEBUG(dbgs() << "Aliasing okay for " << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("licm")) { dbgs() << "Aliasing okay for " << *(MemLoc .Ptr) << "\n"; } } while (false); | |||
| 2252 | return false; | |||
| 2253 | } | |||
| 2254 | ||||
| 2255 | static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, | |||
| 2256 | Loop *CurLoop, | |||
| 2257 | SinkAndHoistLICMFlags &Flags) { | |||
| 2258 | MemoryAccess *Source; | |||
| 2259 | // See declaration of SetLicmMssaOptCap for usage details. | |||
| 2260 | if (Flags.LicmMssaOptCounter >= Flags.LicmMssaOptCap) | |||
| 2261 | Source = MU->getDefiningAccess(); | |||
| 2262 | else { | |||
| 2263 | Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(MU); | |||
| 2264 | Flags.LicmMssaOptCounter++; | |||
| 2265 | } | |||
| 2266 | return !MSSA->isLiveOnEntryDef(Source) && | |||
| 2267 | CurLoop->contains(Source->getBlock()); | |||
| 2268 | } | |||
| 2269 | ||||
| 2270 | /// Little predicate that returns true if the specified basic block is in | |||
| 2271 | /// a subloop of the current one, not the current one itself. | |||
| 2272 | /// | |||
| 2273 | static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) { | |||
| 2274 | assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop")((CurLoop->contains(BB) && "Only valid if BB is IN the loop" ) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(BB) && \"Only valid if BB is IN the loop\"" , "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp" , 2274, __PRETTY_FUNCTION__)); | |||
| 2275 | return LI->getLoopFor(BB) != CurLoop; | |||
| 2276 | } |