1 //===------ SimplifyInstructions.cpp - Remove redundant instructions ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This is a utility pass used for testing the InstructionSimplify analysis.
11 // The analysis is applied to every instruction, and if it simplifies then the
12 // instruction is replaced by the simplification. If you are looking for a pass
13 // that performs serious instruction folding, use the instcombine pass instead.
15 //===----------------------------------------------------------------------===//
17 #define DEBUG_TYPE "instsimplify"
18 #include "llvm/Function.h"
19 #include "llvm/Pass.h"
20 #include "llvm/Type.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/Analysis/InstructionSimplify.h"
24 #include "llvm/Target/TargetData.h"
25 #include "llvm/Transforms/Scalar.h"
26 #include "llvm/Transforms/Utils/Local.h"
29 STATISTIC(NumSimplified, "Number of redundant instructions removed");
32 struct InstSimplifier : public FunctionPass {
33 static char ID; // Pass identification, replacement for typeid
34 InstSimplifier() : FunctionPass(ID) {
35 initializeInstSimplifierPass(*PassRegistry::getPassRegistry());
38 void getAnalysisUsage(AnalysisUsage &AU) const {
42 /// runOnFunction - Remove instructions that simplify.
43 bool runOnFunction(Function &F) {
44 const TargetData *TD = getAnalysisIfAvailable<TargetData>();
45 const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
48 // Add all interesting instructions to the worklist.
49 std::set<Instruction*> Worklist;
50 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
51 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
52 Instruction *I = BI++;
53 // Zap any dead instructions.
54 if (isInstructionTriviallyDead(I)) {
59 // Add all others to the worklist.
63 // Simplify everything in the worklist until the cows come home.
64 while (!Worklist.empty()) {
65 Instruction *I = *Worklist.begin();
66 Worklist.erase(Worklist.begin());
67 Value *V = SimplifyInstruction(I, TD, DT);
70 // This instruction simplifies! Replace it with its simplification and
71 // add all uses to the worklist, since they may now simplify.
72 I->replaceAllUsesWith(V);
73 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
75 // In unreachable code an instruction can use itself, in which case
76 // don't add it to the worklist since we are about to erase it.
77 if (*UI != I) Worklist.insert(cast<Instruction>(*UI));
78 if (isInstructionTriviallyDead(I))
89 char InstSimplifier::ID = 0;
90 INITIALIZE_PASS(InstSimplifier, "instsimplify", "Remove redundant instructions",
92 char &llvm::InstructionSimplifierID = InstSimplifier::ID;
94 // Public interface to the simplify instructions pass.
95 FunctionPass *llvm::createInstructionSimplifierPass() {
96 return new InstSimplifier();