169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands//===------ SimplifyInstructions.cpp - Remove redundant instructions ------===// 269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// 369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// The LLVM Compiler Infrastructure 469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// 569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// This file is distributed under the University of Illinois Open Source 669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// License. See LICENSE.TXT for details. 769fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// 869fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands//===----------------------------------------------------------------------===// 969fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// 1069fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// This is a utility pass used for testing the InstructionSimplify analysis. 1169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// The analysis is applied to every instruction, and if it simplifies then the 1269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// instruction is replaced by the simplification. If you are looking for a pass 1369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// that performs serious instruction folding, use the instcombine pass instead. 1469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// 1569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands//===----------------------------------------------------------------------===// 1669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 1769fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#define DEBUG_TYPE "instsimplify" 1869fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Function.h" 1969fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Pass.h" 2069fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Type.h" 218a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands#include "llvm/ADT/DepthFirstIterator.h" 22dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands#include "llvm/ADT/SmallPtrSet.h" 2369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/ADT/Statistic.h" 2469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Analysis/Dominators.h" 2569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Analysis/InstructionSimplify.h" 2669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Target/TargetData.h" 2769fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands#include "llvm/Transforms/Scalar.h" 28e95cc25a2267128436bb83af6cb57c07323c8693Duncan Sands#include "llvm/Transforms/Utils/Local.h" 2969fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sandsusing namespace llvm; 3069fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 3169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan SandsSTATISTIC(NumSimplified, "Number of redundant instructions removed"); 3269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 3369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sandsnamespace { 3469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands struct InstSimplifier : public FunctionPass { 3569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands static char ID; // Pass identification, replacement for typeid 3669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands InstSimplifier() : FunctionPass(ID) { 3769fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands initializeInstSimplifierPass(*PassRegistry::getPassRegistry()); 3869fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands } 3969fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 4069fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands void getAnalysisUsage(AnalysisUsage &AU) const { 4169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands AU.setPreservesCFG(); 4269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands } 4369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 4469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands /// runOnFunction - Remove instructions that simplify. 4569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands bool runOnFunction(Function &F) { 4669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>(); 478a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands const TargetData *TD = getAnalysisIfAvailable<TargetData>(); 48dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2; 49e95cc25a2267128436bb83af6cb57c07323c8693Duncan Sands bool Changed = false; 50e95cc25a2267128436bb83af6cb57c07323c8693Duncan Sands 518a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands do { 528a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 538a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) 548a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) { 558a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands Instruction *I = BI++; 56dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // The first time through the loop ToSimplify is empty and we try to 57dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // simplify all instructions. On later iterations ToSimplify is not 58dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // empty and we only bother simplifying instructions that are in it. 59dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands if (!ToSimplify->empty() && !ToSimplify->count(I)) 60dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands continue; 61dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // Don't waste time simplifying unused instructions. 628a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands if (!I->use_empty()) 638a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands if (Value *V = SimplifyInstruction(I, TD, DT)) { 64dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // Mark all uses for resimplification next time round the loop. 65dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); 66dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands UI != UE; ++UI) 67dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands Next->insert(cast<Instruction>(*UI)); 688a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands I->replaceAllUsesWith(V); 698a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands ++NumSimplified; 70dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands Changed = true; 718a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands } 72dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands Changed |= RecursivelyDeleteTriviallyDeadInstructions(I); 738a3d29cf1064e8efbb8c8d5d4653ad147c7b037eDuncan Sands } 74e95cc25a2267128436bb83af6cb57c07323c8693Duncan Sands 75dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // Place the list of instructions to simplify on the next loop iteration 76dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands // into ToSimplify. 77dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands std::swap(ToSimplify, Next); 78dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands Next->clear(); 79dc615e41b56daa380e80982097a609bb25afaa82Duncan Sands } while (!ToSimplify->empty()); 801cd0f4637bfb8c93996b09baec8bf2bb220b74caDuncan Sands 8169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands return Changed; 8269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands } 8369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands }; 8469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands} 8569fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 8669fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sandschar InstSimplifier::ID = 0; 8769fdf876e1cceca935561272fd5c238a59c6e9d8Duncan SandsINITIALIZE_PASS(InstSimplifier, "instsimplify", "Remove redundant instructions", 8869fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands false, false) 8969fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sandschar &llvm::InstructionSimplifierID = InstSimplifier::ID; 9069fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands 9169fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands// Public interface to the simplify instructions pass. 9269fdf876e1cceca935561272fd5c238a59c6e9d8Duncan SandsFunctionPass *llvm::createInstructionSimplifierPass() { 9369fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands return new InstSimplifier(); 9469fdf876e1cceca935561272fd5c238a59c6e9d8Duncan Sands} 95