1 //===- LoopInstSimplify.cpp - Loop Instruction Simplification Pass --------===// 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 // This pass performs lightweight instruction simplification on loop bodies. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #define DEBUG_TYPE "loop-instsimplify" 15 #include "llvm/Function.h" 16 #include "llvm/Pass.h" 17 #include "llvm/Analysis/Dominators.h" 18 #include "llvm/Analysis/InstructionSimplify.h" 19 #include "llvm/Analysis/LoopInfo.h" 20 #include "llvm/Target/TargetData.h" 21 #include "llvm/Transforms/Scalar.h" 22 #include "llvm/Transforms/Utils/Local.h" 23 #include "llvm/ADT/Statistic.h" 24 using namespace llvm; 25 26 STATISTIC(NumSimplified, "Number of redundant instructions simplified"); 27 28 namespace { 29 class LoopInstSimplify : public FunctionPass { 30 public: 31 static char ID; // Pass ID, replacement for typeid 32 LoopInstSimplify() : FunctionPass(ID) { 33 initializeLoopInstSimplifyPass(*PassRegistry::getPassRegistry()); 34 } 35 36 bool runOnFunction(Function&); 37 38 virtual void getAnalysisUsage(AnalysisUsage& AU) const { 39 AU.setPreservesCFG(); 40 AU.addRequired<LoopInfo>(); 41 AU.addPreserved<LoopInfo>(); 42 AU.addPreservedID(LCSSAID); 43 } 44 }; 45 } 46 47 char LoopInstSimplify::ID = 0; 48 INITIALIZE_PASS_BEGIN(LoopInstSimplify, "loop-instsimplify", 49 "Simplify instructions in loops", false, false) 50 INITIALIZE_PASS_DEPENDENCY(DominatorTree) 51 INITIALIZE_PASS_DEPENDENCY(LoopInfo) 52 INITIALIZE_PASS_DEPENDENCY(LCSSA) 53 INITIALIZE_PASS_END(LoopInstSimplify, "loop-instsimplify", 54 "Simplify instructions in loops", false, false) 55 56 Pass* llvm::createLoopInstSimplifyPass() { 57 return new LoopInstSimplify(); 58 } 59 60 bool LoopInstSimplify::runOnFunction(Function& F) { 61 DominatorTree* DT = getAnalysisIfAvailable<DominatorTree>(); 62 LoopInfo* LI = &getAnalysis<LoopInfo>(); 63 const TargetData* TD = getAnalysisIfAvailable<TargetData>(); 64 65 bool Changed = false; 66 bool LocalChanged; 67 do { 68 LocalChanged = false; 69 70 for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 71 DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) 72 for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) { 73 Instruction* I = BI++; 74 // Don't bother simplifying unused instructions. 75 if (!I->use_empty()) { 76 Value* V = SimplifyInstruction(I, TD, DT); 77 if (V && LI->replacementPreservesLCSSAForm(I, V)) { 78 I->replaceAllUsesWith(V); 79 LocalChanged = true; 80 ++NumSimplified; 81 } 82 } 83 LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I); 84 } 85 86 Changed |= LocalChanged; 87 } while (LocalChanged); 88 89 return Changed; 90 } 91