1 //===- InstSimplifyPass.cpp -----------------------------------------------===// 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 #include "llvm/Transforms/Scalar/InstSimplifyPass.h" 10 #include "llvm/ADT/DepthFirstIterator.h" 11 #include "llvm/ADT/SmallPtrSet.h" 12 #include "llvm/ADT/Statistic.h" 13 #include "llvm/Analysis/AssumptionCache.h" 14 #include "llvm/Analysis/InstructionSimplify.h" 15 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 16 #include "llvm/Analysis/TargetLibraryInfo.h" 17 #include "llvm/IR/DataLayout.h" 18 #include "llvm/IR/Dominators.h" 19 #include "llvm/IR/Function.h" 20 #include "llvm/IR/Type.h" 21 #include "llvm/Pass.h" 22 #include "llvm/Transforms/Utils.h" 23 #include "llvm/Transforms/Utils/Local.h" 24 using namespace llvm; 25 26 #define DEBUG_TYPE "instsimplify" 27 28 STATISTIC(NumSimplified, "Number of redundant instructions removed"); 29 30 static bool runImpl(Function &F, const SimplifyQuery &SQ, 31 OptimizationRemarkEmitter *ORE) { 32 SmallPtrSet<const Instruction *, 8> S1, S2, *ToSimplify = &S1, *Next = &S2; 33 bool Changed = false; 34 35 do { 36 for (BasicBlock &BB : F) { 37 SmallVector<Instruction *, 8> DeadInstsInBB; 38 for (Instruction &I : BB) { 39 // The first time through the loop, ToSimplify is empty and we try to 40 // simplify all instructions. On later iterations, ToSimplify is not 41 // empty and we only bother simplifying instructions that are in it. 42 if (!ToSimplify->empty() && !ToSimplify->count(&I)) 43 continue; 44 45 // Don't waste time simplifying dead/unused instructions. 46 if (isInstructionTriviallyDead(&I)) { 47 DeadInstsInBB.push_back(&I); 48 } else if (!I.use_empty()) { 49 if (Value *V = SimplifyInstruction(&I, SQ, ORE)) { 50 // Mark all uses for resimplification next time round the loop. 51 for (User *U : I.users()) 52 Next->insert(cast<Instruction>(U)); 53 I.replaceAllUsesWith(V); 54 ++NumSimplified; 55 Changed = true; 56 // A call can get simplified, but it may not be trivially dead. 57 if (isInstructionTriviallyDead(&I)) 58 DeadInstsInBB.push_back(&I); 59 } 60 } 61 } 62 RecursivelyDeleteTriviallyDeadInstructions(DeadInstsInBB, SQ.TLI); 63 } 64 65 // Place the list of instructions to simplify on the next loop iteration 66 // into ToSimplify. 67 std::swap(ToSimplify, Next); 68 Next->clear(); 69 } while (!ToSimplify->empty()); 70 71 return Changed; 72 } 73 74 namespace { 75 struct InstSimplifyLegacyPass : public FunctionPass { 76 static char ID; // Pass identification, replacement for typeid 77 InstSimplifyLegacyPass() : FunctionPass(ID) { 78 initializeInstSimplifyLegacyPassPass(*PassRegistry::getPassRegistry()); 79 } 80 81 void getAnalysisUsage(AnalysisUsage &AU) const override { 82 AU.setPreservesCFG(); 83 AU.addRequired<DominatorTreeWrapperPass>(); 84 AU.addRequired<AssumptionCacheTracker>(); 85 AU.addRequired<TargetLibraryInfoWrapperPass>(); 86 AU.addRequired<OptimizationRemarkEmitterWrapperPass>(); 87 } 88 89 /// runOnFunction - Remove instructions that simplify. 90 bool runOnFunction(Function &F) override { 91 if (skipFunction(F)) 92 return false; 93 94 const DominatorTree *DT = 95 &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 96 const TargetLibraryInfo *TLI = 97 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); 98 AssumptionCache *AC = 99 &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 100 OptimizationRemarkEmitter *ORE = 101 &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE(); 102 const DataLayout &DL = F.getParent()->getDataLayout(); 103 const SimplifyQuery SQ(DL, TLI, DT, AC); 104 return runImpl(F, SQ, ORE); 105 } 106 }; 107 } // namespace 108 109 char InstSimplifyLegacyPass::ID = 0; 110 INITIALIZE_PASS_BEGIN(InstSimplifyLegacyPass, "instsimplify", 111 "Remove redundant instructions", false, false) 112 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 113 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 114 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) 115 INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass) 116 INITIALIZE_PASS_END(InstSimplifyLegacyPass, "instsimplify", 117 "Remove redundant instructions", false, false) 118 119 // Public interface to the simplify instructions pass. 120 FunctionPass *llvm::createInstSimplifyLegacyPass() { 121 return new InstSimplifyLegacyPass(); 122 } 123 124 PreservedAnalyses InstSimplifyPass::run(Function &F, 125 FunctionAnalysisManager &AM) { 126 auto &DT = AM.getResult<DominatorTreeAnalysis>(F); 127 auto &TLI = AM.getResult<TargetLibraryAnalysis>(F); 128 auto &AC = AM.getResult<AssumptionAnalysis>(F); 129 auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F); 130 const DataLayout &DL = F.getParent()->getDataLayout(); 131 const SimplifyQuery SQ(DL, &TLI, &DT, &AC); 132 bool Changed = runImpl(F, SQ, &ORE); 133 if (!Changed) 134 return PreservedAnalyses::all(); 135 136 PreservedAnalyses PA; 137 PA.preserveSet<CFGAnalyses>(); 138 return PA; 139 } 140