SimplifyInstructions.cpp [plain text]
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Type.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
#define DEBUG_TYPE "instsimplify"
STATISTIC(NumSimplified, "Number of redundant instructions removed");
namespace {
struct InstSimplifier : public FunctionPass {
static char ID; InstSimplifier() : FunctionPass(ID) {
initializeInstSimplifierPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
bool runOnFunction(Function &F) override {
const DominatorTreeWrapperPass *DTWP =
getAnalysisIfAvailable<DominatorTreeWrapperPass>();
const DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
const DataLayout &DL = F.getParent()->getDataLayout();
const TargetLibraryInfo *TLI =
&getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
AssumptionCache *AC =
&getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
bool Changed = false;
do {
for (BasicBlock *BB : depth_first(&F.getEntryBlock()))
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = &*BI++;
if (!ToSimplify->empty() && !ToSimplify->count(I))
continue;
if (!I->use_empty())
if (Value *V = SimplifyInstruction(I, DL, TLI, DT, AC)) {
for (User *U : I->users())
Next->insert(cast<Instruction>(U));
I->replaceAllUsesWith(V);
++NumSimplified;
Changed = true;
}
bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
if (res) {
BI = BB->begin(); BE = BB->end();
Changed |= res;
}
}
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(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(InstSimplifier, "instsimplify",
"Remove redundant instructions", false, false)
char &llvm::InstructionSimplifierID = InstSimplifier::ID;
FunctionPass *llvm::createInstructionSimplifierPass() {
return new InstSimplifier();
}