//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This pass performs loop invariant code motion, attempting to remove as much // code from the body of a loop as possible. It does this by either hoisting // code into the preheader block, or by sinking code to the exit blocks if it is // safe. This pass also promotes must-aliased memory locations in the loop to // live in registers, thus hoisting and sinking "invariant" loads and stores. // // Hoisting operations out of loops is a canonicalization transform. It // enables and simplifies subsequent optimizations in the middle-end. // Rematerialization of hoisted instructions to reduce register pressure is the // responsibility of the back-end, which has more accurate information about // register pressure and also handles other optimizations than LICM that // increase live-ranges. // // This pass uses alias analysis for two purposes: // // 1. Moving loop invariant loads and calls out of loops. If we can determine // that a load or call inside of a loop never aliases anything stored to, // we can hoist it or sink it like any other instruction. // 2. Scalar Promotion of Memory - If there is a store instruction inside of // the loop, we try to move the store to happen AFTER the loop instead of // inside of the loop. This can only happen if a few conditions are true: // A. The pointer stored through is loop invariant // B. There are no stores or loads in the loop which _may_ alias the // pointer. There are no calls in the loop which mod/ref the pointer. // If these conditions are true, we can promote the loads and stores in the // loop of the pointer to use a temporary alloca'd variable. We then use // the SSAUpdater to construct the appropriate SSA form for the value. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/Scalar/LICM.h" #include "llvm/ADT/PriorityWorklist.h" #include "llvm/ADT/SetOperations.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Analysis/AliasSetTracker.h" #include "llvm/Analysis/AssumptionCache.h" #include "llvm/Analysis/CaptureTracking.h" #include "llvm/Analysis/DomTreeUpdater.h" #include "llvm/Analysis/GuardUtils.h" #include "llvm/Analysis/LazyBlockFrequencyInfo.h" #include "llvm/Analysis/Loads.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/LoopIterator.h" #include "llvm/Analysis/LoopNestAnalysis.h" #include "llvm/Analysis/LoopPass.h" #include "llvm/Analysis/MemorySSA.h" #include "llvm/Analysis/MemorySSAUpdater.h" #include "llvm/Analysis/MustExecute.h" #include "llvm/Analysis/OptimizationRemarkEmitter.h" #include "llvm/Analysis/ScalarEvolution.h" #include "llvm/Analysis/TargetLibraryInfo.h" #include "llvm/Analysis/TargetTransformInfo.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/IR/CFG.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/DebugInfoMetadata.h" #include "llvm/IR/DerivedTypes.h" #include "llvm/IR/Dominators.h" #include "llvm/IR/IRBuilder.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/LLVMContext.h" #include "llvm/IR/Metadata.h" #include "llvm/IR/PatternMatch.h" #include "llvm/IR/PredIteratorCache.h" #include "llvm/InitializePasses.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetOptions.h" #include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Utils/AssumeBundleBuilder.h" #include "llvm/Transforms/Utils/BasicBlockUtils.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Transforms/Utils/LoopUtils.h" #include "llvm/Transforms/Utils/SSAUpdater.h" #include <algorithm> #include <utility> usingnamespacellvm; namespace llvm { class LPMUpdater; } // namespace llvm #define DEBUG_TYPE … STATISTIC(NumCreatedBlocks, "Number of blocks created"); STATISTIC(NumClonedBranches, "Number of branches cloned"); STATISTIC(NumSunk, "Number of instructions sunk out of loop"); STATISTIC(NumHoisted, "Number of instructions hoisted out of loop"); STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk"); STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk"); STATISTIC(NumPromotionCandidates, "Number of promotion candidates"); STATISTIC(NumLoadPromoted, "Number of load-only promotions"); STATISTIC(NumLoadStorePromoted, "Number of load and store promotions"); STATISTIC(NumMinMaxHoisted, "Number of min/max expressions hoisted out of the loop"); STATISTIC(NumGEPsHoisted, "Number of geps reassociated and hoisted out of the loop"); STATISTIC(NumAddSubHoisted, "Number of add/subtract expressions reassociated " "and hoisted out of the loop"); STATISTIC(NumFPAssociationsHoisted, "Number of invariant FP expressions " "reassociated and hoisted out of the loop"); STATISTIC(NumIntAssociationsHoisted, "Number of invariant int expressions " "reassociated and hoisted out of the loop"); STATISTIC(NumBOAssociationsHoisted, "Number of invariant BinaryOp expressions " "reassociated and hoisted out of the loop"); /// Memory promotion is enabled by default. static cl::opt<bool> DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false), cl::desc("Disable memory promotion in LICM pass")); static cl::opt<bool> ControlFlowHoisting( "licm-control-flow-hoisting", cl::Hidden, cl::init(false), cl::desc("Enable control flow (and PHI) hoisting in LICM")); static cl::opt<bool> SingleThread("licm-force-thread-model-single", cl::Hidden, cl::init(false), cl::desc("Force thread model single in LICM pass")); static cl::opt<uint32_t> MaxNumUsesTraversed( "licm-max-num-uses-traversed", cl::Hidden, cl::init(8), cl::desc("Max num uses visited for identifying load " "invariance in loop using invariant start (default = 8)")); static cl::opt<unsigned> FPAssociationUpperLimit( "licm-max-num-fp-reassociations", cl::init(5U), cl::Hidden, cl::desc( "Set upper limit for the number of transformations performed " "during a single round of hoisting the reassociated expressions.")); cl::opt<unsigned> IntAssociationUpperLimit( "licm-max-num-int-reassociations", cl::init(5U), cl::Hidden, cl::desc( "Set upper limit for the number of transformations performed " "during a single round of hoisting the reassociated expressions.")); // Experimental option to allow imprecision in LICM in pathological cases, in // exchange for faster compile. This is to be removed if MemorySSA starts to // address the same issue. LICM calls MemorySSAWalker's // getClobberingMemoryAccess, up to the value of the Cap, getting perfect // accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess, // which may not be precise, since optimizeUses is capped. The result is // correct, but we may not get as "far up" as possible to get which access is // clobbering the one queried. cl::opt<unsigned> llvm::SetLicmMssaOptCap( "licm-mssa-optimization-cap", cl::init(100), cl::Hidden, cl::desc("Enable imprecision in LICM in pathological cases, in exchange " "for faster compile. Caps the MemorySSA clobbering calls.")); // Experimentally, memory promotion carries less importance than sinking and // hoisting. Limit when we do promotion when using MemorySSA, in order to save // compile time. cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap( "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden, cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no " "effect. When MSSA in LICM is enabled, then this is the maximum " "number of accesses allowed to be present in a loop in order to " "enable memory promotion.")); static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI); static bool isNotUsedOrFoldableInLoop(const Instruction &I, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, TargetTransformInfo *TTI, bool &FoldableInLoop, bool LoopNestMode); static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU, ScalarEvolution *SE, OptimizationRemarkEmitter *ORE); static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU, OptimizationRemarkEmitter *ORE); static bool isSafeToExecuteUnconditionally( Instruction &Inst, const DominatorTree *DT, const TargetLibraryInfo *TLI, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE, const Instruction *CtxI, AssumptionCache *AC, bool AllowSpeculation); static bool pointerInvalidatedByLoop(MemorySSA *MSSA, MemoryUse *MU, Loop *CurLoop, Instruction &I, SinkAndHoistLICMFlags &Flags, bool InvariantGroup); static bool pointerInvalidatedByBlock(BasicBlock &BB, MemorySSA &MSSA, MemoryUse &MU); /// Aggregates various functions for hoisting computations out of loop. static bool hoistArithmetics(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT); static Instruction *cloneInstructionInExitBlock( Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU); static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU); static void moveInstructionBefore(Instruction &I, BasicBlock::iterator Dest, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, ScalarEvolution *SE); static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L, function_ref<void(Instruction *)> Fn); PointersAndHasReadsOutsideSet; static SmallVector<PointersAndHasReadsOutsideSet, 0> collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L); namespace { struct LoopInvariantCodeMotion { … }; struct LegacyLICMPass : public LoopPass { … }; } // namespace PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR, LPMUpdater &) { … } void LICMPass::printPipeline( raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { … } PreservedAnalyses LNICMPass::run(LoopNest &LN, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR, LPMUpdater &) { … } void LNICMPass::printPipeline( raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { … } char LegacyLICMPass::ID = …; INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false, false) INITIALIZE_PASS_DEPENDENCY(LoopPass) INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass) INITIALIZE_PASS_DEPENDENCY(LazyBFIPass) INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false, false) Pass *llvm::createLICMPass() { … } llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags(bool IsSink, Loop &L, MemorySSA &MSSA) : … { … } llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags( unsigned LicmMssaOptCap, unsigned LicmMssaNoAccForPromotionCap, bool IsSink, Loop &L, MemorySSA &MSSA) : … { … } /// Hoist expressions out of the specified loop. Note, alias info for inner /// loop is not preserved so it is not a good idea to run LICM multiple /// times on one loop. bool LoopInvariantCodeMotion::runOnLoop(Loop *L, AAResults *AA, LoopInfo *LI, DominatorTree *DT, AssumptionCache *AC, TargetLibraryInfo *TLI, TargetTransformInfo *TTI, ScalarEvolution *SE, MemorySSA *MSSA, OptimizationRemarkEmitter *ORE, bool LoopNestMode) { … } /// Walk the specified region of the CFG (defined by all blocks dominated by /// the specified block, and that are in the current loop) in reverse depth /// first order w.r.t the DominatorTree. This allows us to visit uses before /// definitions, allowing us to sink a loop body in one pass without iteration. /// bool llvm::sinkRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI, DominatorTree *DT, TargetLibraryInfo *TLI, TargetTransformInfo *TTI, Loop *CurLoop, MemorySSAUpdater &MSSAU, ICFLoopSafetyInfo *SafetyInfo, SinkAndHoistLICMFlags &Flags, OptimizationRemarkEmitter *ORE, Loop *OutermostLoop) { … } bool llvm::sinkRegionForLoopNest(DomTreeNode *N, AAResults *AA, LoopInfo *LI, DominatorTree *DT, TargetLibraryInfo *TLI, TargetTransformInfo *TTI, Loop *CurLoop, MemorySSAUpdater &MSSAU, ICFLoopSafetyInfo *SafetyInfo, SinkAndHoistLICMFlags &Flags, OptimizationRemarkEmitter *ORE) { … } namespace { // This is a helper class for hoistRegion to make it able to hoist control flow // in order to be able to hoist phis. The way this works is that we initially // start hoisting to the loop preheader, and when we see a loop invariant branch // we make note of this. When we then come to hoist an instruction that's // conditional on such a branch we duplicate the branch and the relevant control // flow, then hoist the instruction into the block corresponding to its original // block in the duplicated control flow. class ControlFlowHoister { … }; } // namespace /// Walk the specified region of the CFG (defined by all blocks dominated by /// the specified block, and that are in the current loop) in depth first /// order w.r.t the DominatorTree. This allows us to visit definitions before /// uses, allowing us to hoist a loop body in one pass without iteration. /// bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI, DominatorTree *DT, AssumptionCache *AC, TargetLibraryInfo *TLI, Loop *CurLoop, MemorySSAUpdater &MSSAU, ScalarEvolution *SE, ICFLoopSafetyInfo *SafetyInfo, SinkAndHoistLICMFlags &Flags, OptimizationRemarkEmitter *ORE, bool LoopNestMode, bool AllowSpeculation) { … } // Return true if LI is invariant within scope of the loop. LI is invariant if // CurLoop is dominated by an invariant.start representing the same memory // location and size as the memory location LI loads from, and also the // invariant.start has no uses. static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT, Loop *CurLoop) { … } namespace { /// Return true if-and-only-if we know how to (mechanically) both hoist and /// sink a given instruction out of a loop. Does not address legality /// concerns such as aliasing or speculation safety. bool isHoistableAndSinkableInst(Instruction &I) { … } /// Return true if MSSA knows there are no MemoryDefs in the loop. bool isReadOnly(const MemorySSAUpdater &MSSAU, const Loop *L) { … } /// Return true if I is the only Instruction with a MemoryAccess in L. bool isOnlyMemoryAccess(const Instruction *I, const Loop *L, const MemorySSAUpdater &MSSAU) { … } } static MemoryAccess *getClobberingMemoryAccess(MemorySSA &MSSA, BatchAAResults &BAA, SinkAndHoistLICMFlags &Flags, MemoryUseOrDef *MA) { … } bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, Loop *CurLoop, MemorySSAUpdater &MSSAU, bool TargetExecutesOncePerLoop, SinkAndHoistLICMFlags &Flags, OptimizationRemarkEmitter *ORE) { … } /// Returns true if a PHINode is a trivially replaceable with an /// Instruction. /// This is true when all incoming values are that instruction. /// This pattern occurs most often with LCSSA PHI nodes. /// static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) { … } /// Return true if the instruction is foldable in the loop. static bool isFoldableInLoop(const Instruction &I, const Loop *CurLoop, const TargetTransformInfo *TTI) { … } /// Return true if the only users of this instruction are outside of /// the loop. If this is true, we can sink the instruction to the exit /// blocks of the loop. /// /// We also return true if the instruction could be folded away in lowering. /// (e.g., a GEP can be folded into a load as an addressing mode in the loop). static bool isNotUsedOrFoldableInLoop(const Instruction &I, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, TargetTransformInfo *TTI, bool &FoldableInLoop, bool LoopNestMode) { … } static Instruction *cloneInstructionInExitBlock( Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU) { … } static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU) { … } static void moveInstructionBefore(Instruction &I, BasicBlock::iterator Dest, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, ScalarEvolution *SE) { … } static Instruction *sinkThroughTriviallyReplaceablePHI( PHINode *TPN, Instruction *I, LoopInfo *LI, SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies, const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop, MemorySSAUpdater &MSSAU) { … } static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) { … } static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT, LoopInfo *LI, const Loop *CurLoop, LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) { … } /// When an instruction is found to only be used outside of the loop, this /// function moves it to the exit blocks and patches up SSA form as needed. /// This method is guaranteed to remove the original instruction from its /// position, and may either delete it or move it to outside of the loop. /// static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU, OptimizationRemarkEmitter *ORE) { … } /// When an instruction is found to only use loop invariant operands that /// is safe to hoist, this instruction is called to do the dirty work. /// static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater &MSSAU, ScalarEvolution *SE, OptimizationRemarkEmitter *ORE) { … } /// Only sink or hoist an instruction if it is not a trapping instruction, /// or if the instruction is known not to trap when moved to the preheader. /// or if it is a trapping instruction and is guaranteed to execute. static bool isSafeToExecuteUnconditionally( Instruction &Inst, const DominatorTree *DT, const TargetLibraryInfo *TLI, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE, const Instruction *CtxI, AssumptionCache *AC, bool AllowSpeculation) { … } namespace { class LoopPromoter : public LoadAndStorePromoter { … }; bool isNotCapturedBeforeOrInLoop(const Value *V, const Loop *L, DominatorTree *DT) { … } /// Return true if we can prove that a caller cannot inspect the object if an /// unwind occurs inside the loop. bool isNotVisibleOnUnwindInLoop(const Value *Object, const Loop *L, DominatorTree *DT) { … } bool isThreadLocalObject(const Value *Object, const Loop *L, DominatorTree *DT, TargetTransformInfo *TTI) { … } } // namespace /// Try to promote memory values to scalars by sinking stores out of the /// loop and moving loads to before the loop. We do this by looping over /// the stores in the loop, looking for stores to Must pointers which are /// loop invariant. /// bool llvm::promoteLoopAccessesToScalars( const SmallSetVector<Value *, 8> &PointerMustAliases, SmallVectorImpl<BasicBlock *> &ExitBlocks, SmallVectorImpl<BasicBlock::iterator> &InsertPts, SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC, LoopInfo *LI, DominatorTree *DT, AssumptionCache *AC, const TargetLibraryInfo *TLI, TargetTransformInfo *TTI, Loop *CurLoop, MemorySSAUpdater &MSSAU, ICFLoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE, bool AllowSpeculation, bool HasReadsOutsideSet) { … } static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L, function_ref<void(Instruction *)> Fn) { … } // The bool indicates whether there might be reads outside the set, in which // case only loads may be promoted. static SmallVector<PointersAndHasReadsOutsideSet, 0> collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L) { … } static bool pointerInvalidatedByLoop(MemorySSA *MSSA, MemoryUse *MU, Loop *CurLoop, Instruction &I, SinkAndHoistLICMFlags &Flags, bool InvariantGroup) { … } bool pointerInvalidatedByBlock(BasicBlock &BB, MemorySSA &MSSA, MemoryUse &MU) { … } /// Try to simplify things like (A < INV_1 AND icmp A < INV_2) into (A < /// min(INV_1, INV_2)), if INV_1 and INV_2 are both loop invariants and their /// minimun can be computed outside of loop, and X is not a loop-invariant. static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU) { … } /// Reassociate gep (gep ptr, idx1), idx2 to gep (gep ptr, idx2), idx1 if /// this allows hoisting the inner GEP. static bool hoistGEP(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } /// Try to turn things like "LV + C1 < C2" into "LV < C2 - C1". Here /// C1 and C2 are loop invariants and LV is a loop-variant. static bool hoistAdd(ICmpInst::Predicate Pred, Value *VariantLHS, Value *InvariantRHS, ICmpInst &ICmp, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } /// Try to reassociate and hoist the following two patterns: /// LV - C1 < C2 --> LV < C1 + C2, /// C1 - LV < C2 --> LV > C1 - C2. static bool hoistSub(ICmpInst::Predicate Pred, Value *VariantLHS, Value *InvariantRHS, ICmpInst &ICmp, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } /// Reassociate and hoist add/sub expressions. static bool hoistAddSub(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } static bool isReassociableOp(Instruction *I, unsigned IntOpcode, unsigned FPOpcode) { … } /// Try to reassociate expressions like ((A1 * B1) + (A2 * B2) + ...) * C where /// A1, A2, ... and C are loop invariants into expressions like /// ((A1 * C * B1) + (A2 * C * B2) + ...) and hoist the (A1 * C), (A2 * C), ... /// invariant expressions. This functions returns true only if any hoisting has /// actually occured. static bool hoistMulAddAssociation(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } /// Reassociate associative binary expressions of the form /// /// 1. "(LV op C1) op C2" ==> "LV op (C1 op C2)" /// 2. "(C1 op LV) op C2" ==> "LV op (C1 op C2)" /// 3. "C2 op (C1 op LV)" ==> "LV op (C1 op C2)" /// 4. "C2 op (LV op C1)" ==> "LV op (C1 op C2)" /// /// where op is an associative BinOp, LV is a loop variant, and C1 and C2 are /// loop invariants that we want to hoist, noting that associativity implies /// commutativity. static bool hoistBOAssociation(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } static bool hoistArithmetics(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo, MemorySSAUpdater &MSSAU, AssumptionCache *AC, DominatorTree *DT) { … } /// Little predicate that returns true if the specified basic block is in /// a subloop of the current one, not the current one itself. /// static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) { … }
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