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//===------ SimplifyInstructions.cpp - Remove redundant instructions ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a utility pass used for testing the InstructionSimplify analysis.
// The analysis is applied to every instruction, and if it simplifies then the
// instruction is replaced by the simplification. If you are looking for a pass
// that performs serious instruction folding, use the instcombine pass instead.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "instsimplify"
#include "llvm/Function.h"
#include "llvm/Pass.h"
#include "llvm/Type.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Scalar.h"
using namespace llvm;
STATISTIC(NumSimplified, "Number of redundant instructions removed");
namespace {
struct InstSimplifier : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
InstSimplifier() : FunctionPass(ID) {
initializeInstSimplifierPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
}
/// runOnFunction - Remove instructions that simplify.
bool runOnFunction(Function &F) {
bool Changed = false;
const TargetData *TD = getAnalysisIfAvailable<TargetData>();
const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = BI++;
if (Value *V = SimplifyInstruction(I, TD, DT)) {
I->replaceAllUsesWith(V);
I->eraseFromParent();
Changed = true;
++NumSimplified;
}
}
return Changed;
}
};
}
char InstSimplifier::ID = 0;
INITIALIZE_PASS(InstSimplifier, "instsimplify", "Remove redundant instructions",
false, false)
char &llvm::InstructionSimplifierID = InstSimplifier::ID;
// Public interface to the simplify instructions pass.
FunctionPass *llvm::createInstructionSimplifierPass() {
return new InstSimplifier();
}
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