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//===- LoopInstSimplify.cpp - Loop Instruction Simplification Pass --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs lightweight instruction simplification on loop bodies.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-instsimplify"
#include "llvm/Function.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumSimplified, "Number of redundant instructions simplified");
namespace {
class LoopInstSimplify : public FunctionPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopInstSimplify() : FunctionPass(ID) {
initializeLoopInstSimplifyPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function&);
virtual void getAnalysisUsage(AnalysisUsage& AU) const {
AU.setPreservesCFG();
AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
AU.addPreservedID(LCSSAID);
}
};
}
char LoopInstSimplify::ID = 0;
INITIALIZE_PASS_BEGIN(LoopInstSimplify, "loop-instsimplify",
"Simplify instructions in loops", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_END(LoopInstSimplify, "loop-instsimplify",
"Simplify instructions in loops", false, false)
Pass* llvm::createLoopInstSimplifyPass() {
return new LoopInstSimplify();
}
bool LoopInstSimplify::runOnFunction(Function& F) {
DominatorTree* DT = getAnalysisIfAvailable<DominatorTree>();
LoopInfo* LI = &getAnalysis<LoopInfo>();
const TargetData* TD = getAnalysisIfAvailable<TargetData>();
bool Changed = false;
bool LocalChanged;
do {
LocalChanged = false;
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++;
// Don't bother simplifying unused instructions.
if (!I->use_empty()) {
Value* V = SimplifyInstruction(I, TD, DT);
if (V && LI->replacementPreservesLCSSAForm(I, V)) {
I->replaceAllUsesWith(V);
LocalChanged = true;
++NumSimplified;
}
}
LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I);
}
Changed |= LocalChanged;
} while (LocalChanged);
return Changed;
}
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