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 17249423Sdim#include "llvm/Transforms/Scalar.h" 18218885Sdim#include "llvm/ADT/DepthFirstIterator.h" 19218885Sdim#include "llvm/ADT/SmallPtrSet.h" 20218885Sdim#include "llvm/ADT/Statistic.h" 21280031Sdim#include "llvm/Analysis/AssumptionCache.h" 22218885Sdim#include "llvm/Analysis/InstructionSimplify.h" 23296417Sdim#include "llvm/Analysis/TargetLibraryInfo.h" 24249423Sdim#include "llvm/IR/DataLayout.h" 25276479Sdim#include "llvm/IR/Dominators.h" 26249423Sdim#include "llvm/IR/Function.h" 27249423Sdim#include "llvm/IR/Type.h" 28249423Sdim#include "llvm/Pass.h" 29218885Sdim#include "llvm/Transforms/Utils/Local.h" 30218885Sdimusing namespace llvm; 31218885Sdim 32276479Sdim#define DEBUG_TYPE "instsimplify" 33276479Sdim 34218885SdimSTATISTIC(NumSimplified, "Number of redundant instructions removed"); 35218885Sdim 36218885Sdimnamespace { 37218885Sdim struct InstSimplifier : public FunctionPass { 38218885Sdim static char ID; // Pass identification, replacement for typeid 39218885Sdim InstSimplifier() : FunctionPass(ID) { 40218885Sdim initializeInstSimplifierPass(*PassRegistry::getPassRegistry()); 41218885Sdim } 42218885Sdim 43276479Sdim void getAnalysisUsage(AnalysisUsage &AU) const override { 44218885Sdim AU.setPreservesCFG(); 45280031Sdim AU.addRequired<AssumptionCacheTracker>(); 46288943Sdim AU.addRequired<TargetLibraryInfoWrapperPass>(); 47218885Sdim } 48218885Sdim 49218885Sdim /// runOnFunction - Remove instructions that simplify. 50276479Sdim bool runOnFunction(Function &F) override { 51276479Sdim const DominatorTreeWrapperPass *DTWP = 52276479Sdim getAnalysisIfAvailable<DominatorTreeWrapperPass>(); 53276479Sdim const DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr; 54288943Sdim const DataLayout &DL = F.getParent()->getDataLayout(); 55288943Sdim const TargetLibraryInfo *TLI = 56288943Sdim &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); 57280031Sdim AssumptionCache *AC = 58280031Sdim &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 59218885Sdim SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2; 60218885Sdim bool Changed = false; 61218885Sdim 62218885Sdim do { 63276479Sdim for (BasicBlock *BB : depth_first(&F.getEntryBlock())) 64276479Sdim // Here be subtlety: the iterator must be incremented before the loop 65276479Sdim // body (not sure why), so a range-for loop won't work here. 66276479Sdim for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) { 67296417Sdim Instruction *I = &*BI++; 68218885Sdim // The first time through the loop ToSimplify is empty and we try to 69218885Sdim // simplify all instructions. On later iterations ToSimplify is not 70218885Sdim // empty and we only bother simplifying instructions that are in it. 71218885Sdim if (!ToSimplify->empty() && !ToSimplify->count(I)) 72218885Sdim continue; 73218885Sdim // Don't waste time simplifying unused instructions. 74218885Sdim if (!I->use_empty()) 75280031Sdim if (Value *V = SimplifyInstruction(I, DL, TLI, DT, AC)) { 76218885Sdim // Mark all uses for resimplification next time round the loop. 77276479Sdim for (User *U : I->users()) 78276479Sdim Next->insert(cast<Instruction>(U)); 79218885Sdim I->replaceAllUsesWith(V); 80218885Sdim ++NumSimplified; 81218885Sdim Changed = true; 82218885Sdim } 83276479Sdim bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI); 84276479Sdim if (res) { 85276479Sdim // RecursivelyDeleteTriviallyDeadInstruction can remove 86276479Sdim // more than one instruction, so simply incrementing the 87276479Sdim // iterator does not work. When instructions get deleted 88276479Sdim // re-iterate instead. 89276479Sdim BI = BB->begin(); BE = BB->end(); 90276479Sdim Changed |= res; 91276479Sdim } 92218885Sdim } 93218885Sdim 94218885Sdim // Place the list of instructions to simplify on the next loop iteration 95218885Sdim // into ToSimplify. 96218885Sdim std::swap(ToSimplify, Next); 97218885Sdim Next->clear(); 98218885Sdim } while (!ToSimplify->empty()); 99218885Sdim 100218885Sdim return Changed; 101218885Sdim } 102218885Sdim }; 103218885Sdim} 104218885Sdim 105218885Sdimchar InstSimplifier::ID = 0; 106234353SdimINITIALIZE_PASS_BEGIN(InstSimplifier, "instsimplify", 107234353Sdim "Remove redundant instructions", false, false) 108280031SdimINITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 109288943SdimINITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) 110234353SdimINITIALIZE_PASS_END(InstSimplifier, "instsimplify", 111234353Sdim "Remove redundant instructions", false, false) 112218885Sdimchar &llvm::InstructionSimplifierID = InstSimplifier::ID; 113218885Sdim 114218885Sdim// Public interface to the simplify instructions pass. 115218885SdimFunctionPass *llvm::createInstructionSimplifierPass() { 116218885Sdim return new InstSimplifier(); 117218885Sdim} 118