1218885Sdim//===------ SimplifyInstructions.cpp - Remove redundant instructions ------===// 2218885Sdim// 3218885Sdim// The LLVM Compiler Infrastructure 4218885Sdim// 5218885Sdim// This file is distributed under the University of Illinois Open Source 6218885Sdim// License. See LICENSE.TXT for details. 7218885Sdim// 8218885Sdim//===----------------------------------------------------------------------===// 9218885Sdim// 10218885Sdim// This is a utility pass used for testing the InstructionSimplify analysis. 11218885Sdim// The analysis is applied to every instruction, and if it simplifies then the 12218885Sdim// instruction is replaced by the simplification. If you are looking for a pass 13218885Sdim// that performs serious instruction folding, use the instcombine pass instead. 14218885Sdim// 15218885Sdim//===----------------------------------------------------------------------===// 16218885Sdim 17218885Sdim#define DEBUG_TYPE "instsimplify" 18249423Sdim#include "llvm/Transforms/Scalar.h" 19218885Sdim#include "llvm/ADT/DepthFirstIterator.h" 20218885Sdim#include "llvm/ADT/SmallPtrSet.h" 21218885Sdim#include "llvm/ADT/Statistic.h" 22218885Sdim#include "llvm/Analysis/Dominators.h" 23218885Sdim#include "llvm/Analysis/InstructionSimplify.h" 24249423Sdim#include "llvm/IR/DataLayout.h" 25249423Sdim#include "llvm/IR/Function.h" 26249423Sdim#include "llvm/IR/Type.h" 27249423Sdim#include "llvm/Pass.h" 28234353Sdim#include "llvm/Target/TargetLibraryInfo.h" 29218885Sdim#include "llvm/Transforms/Utils/Local.h" 30218885Sdimusing namespace llvm; 31218885Sdim 32218885SdimSTATISTIC(NumSimplified, "Number of redundant instructions removed"); 33218885Sdim 34218885Sdimnamespace { 35218885Sdim struct InstSimplifier : public FunctionPass { 36218885Sdim static char ID; // Pass identification, replacement for typeid 37218885Sdim InstSimplifier() : FunctionPass(ID) { 38218885Sdim initializeInstSimplifierPass(*PassRegistry::getPassRegistry()); 39218885Sdim } 40218885Sdim 41218885Sdim void getAnalysisUsage(AnalysisUsage &AU) const { 42218885Sdim AU.setPreservesCFG(); 43234353Sdim AU.addRequired<TargetLibraryInfo>(); 44218885Sdim } 45218885Sdim 46218885Sdim /// runOnFunction - Remove instructions that simplify. 47218885Sdim bool runOnFunction(Function &F) { 48218885Sdim const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>(); 49243830Sdim const DataLayout *TD = getAnalysisIfAvailable<DataLayout>(); 50234353Sdim const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>(); 51218885Sdim SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2; 52218885Sdim bool Changed = false; 53218885Sdim 54218885Sdim do { 55218885Sdim for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 56218885Sdim DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) 57218885Sdim for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) { 58218885Sdim Instruction *I = BI++; 59218885Sdim // The first time through the loop ToSimplify is empty and we try to 60218885Sdim // simplify all instructions. On later iterations ToSimplify is not 61218885Sdim // empty and we only bother simplifying instructions that are in it. 62218885Sdim if (!ToSimplify->empty() && !ToSimplify->count(I)) 63218885Sdim continue; 64218885Sdim // Don't waste time simplifying unused instructions. 65218885Sdim if (!I->use_empty()) 66234353Sdim if (Value *V = SimplifyInstruction(I, TD, TLI, DT)) { 67218885Sdim // Mark all uses for resimplification next time round the loop. 68218885Sdim for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); 69218885Sdim UI != UE; ++UI) 70218885Sdim Next->insert(cast<Instruction>(*UI)); 71218885Sdim I->replaceAllUsesWith(V); 72218885Sdim ++NumSimplified; 73218885Sdim Changed = true; 74218885Sdim } 75243830Sdim Changed |= RecursivelyDeleteTriviallyDeadInstructions(I, TLI); 76218885Sdim } 77218885Sdim 78218885Sdim // Place the list of instructions to simplify on the next loop iteration 79218885Sdim // into ToSimplify. 80218885Sdim std::swap(ToSimplify, Next); 81218885Sdim Next->clear(); 82218885Sdim } while (!ToSimplify->empty()); 83218885Sdim 84218885Sdim return Changed; 85218885Sdim } 86218885Sdim }; 87218885Sdim} 88218885Sdim 89218885Sdimchar InstSimplifier::ID = 0; 90234353SdimINITIALIZE_PASS_BEGIN(InstSimplifier, "instsimplify", 91234353Sdim "Remove redundant instructions", false, false) 92234353SdimINITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 93234353SdimINITIALIZE_PASS_END(InstSimplifier, "instsimplify", 94234353Sdim "Remove redundant instructions", false, false) 95218885Sdimchar &llvm::InstructionSimplifierID = InstSimplifier::ID; 96218885Sdim 97218885Sdim// Public interface to the simplify instructions pass. 98218885SdimFunctionPass *llvm::createInstructionSimplifierPass() { 99218885Sdim return new InstSimplifier(); 100218885Sdim} 101