1 //===- InstSimplifyPass.cpp -----------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "llvm/Transforms/Scalar/InstSimplifyPass.h" 11 #include "llvm/ADT/DepthFirstIterator.h" 12 #include "llvm/ADT/SmallPtrSet.h" 13 #include "llvm/ADT/Statistic.h" 14 #include "llvm/Analysis/AssumptionCache.h" 15 #include "llvm/Analysis/InstructionSimplify.h" 16 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 17 #include "llvm/Analysis/TargetLibraryInfo.h" 18 #include "llvm/IR/DataLayout.h" 19 #include "llvm/IR/Dominators.h" 20 #include "llvm/IR/Function.h" 21 #include "llvm/IR/Type.h" 22 #include "llvm/Pass.h" 23 #include "llvm/Transforms/Utils.h" 24 #include "llvm/Transforms/Utils/Local.h" 25 using namespace llvm; 26 27 #define DEBUG_TYPE "instsimplify" 28 29 STATISTIC(NumSimplified, "Number of redundant instructions removed"); 30 31 static bool runImpl(Function &F, const SimplifyQuery &SQ, 32 OptimizationRemarkEmitter *ORE) { 33 SmallPtrSet<const Instruction *, 8> S1, S2, *ToSimplify = &S1, *Next = &S2; 34 bool Changed = false; 35 36 do { 37 for (BasicBlock *BB : depth_first(&F.getEntryBlock())) { 38 // Here be subtlety: the iterator must be incremented before the loop 39 // body (not sure why), so a range-for loop won't work here. 40 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) { 41 Instruction *I = &*BI++; 42 // The first time through the loop ToSimplify is empty and we try to 43 // simplify all instructions. On later iterations ToSimplify is not 44 // empty and we only bother simplifying instructions that are in it. 45 if (!ToSimplify->empty() && !ToSimplify->count(I)) 46 continue; 47 48 // Don't waste time simplifying unused instructions. 49 if (!I->use_empty()) { 50 if (Value *V = SimplifyInstruction(I, SQ, ORE)) { 51 // Mark all uses for resimplification next time round the loop. 52 for (User *U : I->users()) 53 Next->insert(cast<Instruction>(U)); 54 I->replaceAllUsesWith(V); 55 ++NumSimplified; 56 Changed = true; 57 } 58 } 59 if (RecursivelyDeleteTriviallyDeadInstructions(I, SQ.TLI)) { 60 // RecursivelyDeleteTriviallyDeadInstruction can remove more than one 61 // instruction, so simply incrementing the iterator does not work. 62 // When instructions get deleted re-iterate instead. 63 BI = BB->begin(); 64 BE = BB->end(); 65 Changed = true; 66 } 67 } 68 } 69 70 // Place the list of instructions to simplify on the next loop iteration 71 // into ToSimplify. 72 std::swap(ToSimplify, Next); 73 Next->clear(); 74 } while (!ToSimplify->empty()); 75 76 return Changed; 77 } 78 79 namespace { 80 struct InstSimplifyLegacyPass : public FunctionPass { 81 static char ID; // Pass identification, replacement for typeid 82 InstSimplifyLegacyPass() : FunctionPass(ID) { 83 initializeInstSimplifyLegacyPassPass(*PassRegistry::getPassRegistry()); 84 } 85 86 void getAnalysisUsage(AnalysisUsage &AU) const override { 87 AU.setPreservesCFG(); 88 AU.addRequired<DominatorTreeWrapperPass>(); 89 AU.addRequired<AssumptionCacheTracker>(); 90 AU.addRequired<TargetLibraryInfoWrapperPass>(); 91 AU.addRequired<OptimizationRemarkEmitterWrapperPass>(); 92 } 93 94 /// runOnFunction - Remove instructions that simplify. 95 bool runOnFunction(Function &F) override { 96 if (skipFunction(F)) 97 return false; 98 99 const DominatorTree *DT = 100 &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 101 const TargetLibraryInfo *TLI = 102 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); 103 AssumptionCache *AC = 104 &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 105 OptimizationRemarkEmitter *ORE = 106 &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE(); 107 const DataLayout &DL = F.getParent()->getDataLayout(); 108 const SimplifyQuery SQ(DL, TLI, DT, AC); 109 return runImpl(F, SQ, ORE); 110 } 111 }; 112 } // namespace 113 114 char InstSimplifyLegacyPass::ID = 0; 115 INITIALIZE_PASS_BEGIN(InstSimplifyLegacyPass, "instsimplify", 116 "Remove redundant instructions", false, false) 117 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 118 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 119 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) 120 INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass) 121 INITIALIZE_PASS_END(InstSimplifyLegacyPass, "instsimplify", 122 "Remove redundant instructions", false, false) 123 124 // Public interface to the simplify instructions pass. 125 FunctionPass *llvm::createInstSimplifyLegacyPass() { 126 return new InstSimplifyLegacyPass(); 127 } 128 129 PreservedAnalyses InstSimplifyPass::run(Function &F, 130 FunctionAnalysisManager &AM) { 131 auto &DT = AM.getResult<DominatorTreeAnalysis>(F); 132 auto &TLI = AM.getResult<TargetLibraryAnalysis>(F); 133 auto &AC = AM.getResult<AssumptionAnalysis>(F); 134 auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F); 135 const DataLayout &DL = F.getParent()->getDataLayout(); 136 const SimplifyQuery SQ(DL, &TLI, &DT, &AC); 137 bool Changed = runImpl(F, SQ, &ORE); 138 if (!Changed) 139 return PreservedAnalyses::all(); 140 141 PreservedAnalyses PA; 142 PA.preserveSet<CFGAnalyses>(); 143 return PA; 144 } 145