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operands are visited before the instructions themselves. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122647 91177308-0d34-0410-b5e6-96231b3b80d8
84 lines
2.9 KiB
C++
84 lines
2.9 KiB
C++
//===------ SimplifyInstructions.cpp - Remove redundant instructions ------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This is a utility pass used for testing the InstructionSimplify analysis.
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// The analysis is applied to every instruction, and if it simplifies then the
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// instruction is replaced by the simplification. If you are looking for a pass
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// that performs serious instruction folding, use the instcombine pass instead.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "instsimplify"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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#include "llvm/Type.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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STATISTIC(NumSimplified, "Number of redundant instructions removed");
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namespace {
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struct InstSimplifier : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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InstSimplifier() : FunctionPass(ID) {
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initializeInstSimplifierPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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}
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/// runOnFunction - Remove instructions that simplify.
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bool runOnFunction(Function &F) {
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const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
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const TargetData *TD = getAnalysisIfAvailable<TargetData>();
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bool Changed = false;
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bool LocalChanged;
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do {
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LocalChanged = false;
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for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
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DE = df_end(&F.getEntryBlock()); DI != DE; ++DI)
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for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) {
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Instruction *I = BI++;
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// Don't bother simplifying unused instructions.
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if (!I->use_empty())
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if (Value *V = SimplifyInstruction(I, TD, DT)) {
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I->replaceAllUsesWith(V);
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LocalChanged = true;
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++NumSimplified;
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}
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LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I);
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}
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Changed |= LocalChanged;
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} while (LocalChanged);
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return Changed;
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}
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};
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}
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char InstSimplifier::ID = 0;
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INITIALIZE_PASS(InstSimplifier, "instsimplify", "Remove redundant instructions",
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false, false)
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char &llvm::InstructionSimplifierID = InstSimplifier::ID;
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// Public interface to the simplify instructions pass.
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FunctionPass *llvm::createInstructionSimplifierPass() {
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return new InstSimplifier();
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}
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