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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/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/DataLayout.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.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();
AU.addRequired<TargetLibraryInfo>();
}
/// runOnFunction - Remove instructions that simplify.
bool runOnFunction(Function &F) {
const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
const DataLayout *TD = getAnalysisIfAvailable<DataLayout>();
const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>();
SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
bool Changed = false;
do {
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
DE = df_end(&F.getEntryBlock()); DI != DE; ++DI)
for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) {
Instruction *I = BI++;
// The first time through the loop ToSimplify is empty and we try to
// simplify all instructions. On later iterations ToSimplify is not
// empty and we only bother simplifying instructions that are in it.
if (!ToSimplify->empty() && !ToSimplify->count(I))
continue;
// Don't waste time simplifying unused instructions.
if (!I->use_empty())
if (Value *V = SimplifyInstruction(I, TD, TLI, DT)) {
// Mark all uses for resimplification next time round the loop.
for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE; ++UI)
Next->insert(cast<Instruction>(*UI));
I->replaceAllUsesWith(V);
++NumSimplified;
Changed = true;
}
Changed |= RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
}
// Place the list of instructions to simplify on the next loop iteration
// into ToSimplify.
std::swap(ToSimplify, Next);
Next->clear();
} while (!ToSimplify->empty());
return Changed;
}
};
}
char InstSimplifier::ID = 0;
INITIALIZE_PASS_BEGIN(InstSimplifier, "instsimplify",
"Remove redundant instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_PASS_END(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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