#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
if (skipOptnoneFunction(F))
return false;
- AA = &getAnalysis<AliasAnalysis>();
+ AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
MD = &getAnalysis<MemoryDependenceAnalysis>();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
}
bool runOnBasicBlock(BasicBlock &BB);
- bool MemoryIsNotModifiedBetween(LoadInst *LI, StoreInst *SI);
+ bool MemoryIsNotModifiedBetween(Instruction *FirstI, Instruction *SecondI);
bool HandleFree(CallInst *F);
bool handleEndBlock(BasicBlock &BB);
void RemoveAccessedObjects(const MemoryLocation &LoadedLoc,
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<DominatorTreeWrapperPass>();
- AU.addRequired<AliasAnalysis>();
+ AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<MemoryDependenceAnalysis>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
- AU.addPreserved<AliasAnalysis>();
AU.addPreserved<DominatorTreeWrapperPass>();
+ AU.addPreserved<GlobalsAAWrapperPass>();
AU.addPreserved<MemoryDependenceAnalysis>();
}
};
char DSE::ID = 0;
INITIALIZE_PASS_BEGIN(DSE, "dse", "Dead Store Elimination", false, false)
-INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(DSE, "dse", "Dead Store Elimination", false, false)
//===----------------------------------------------------------------------===//
bool DSE::runOnBasicBlock(BasicBlock &BB) {
+ const DataLayout &DL = BB.getModule()->getDataLayout();
bool MadeChange = false;
// Do a top-down walk on the BB.
// If we're storing the same value back to a pointer that we just
// loaded from, then the store can be removed.
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+
+ auto RemoveDeadInstAndUpdateBBI = [&](Instruction *DeadInst) {
+ // DeleteDeadInstruction can delete the current instruction. Save BBI
+ // in case we need it.
+ WeakVH NextInst(BBI);
+
+ DeleteDeadInstruction(DeadInst, *MD, *TLI);
+
+ if (!NextInst) // Next instruction deleted.
+ BBI = BB.begin();
+ else if (BBI != BB.begin()) // Revisit this instruction if possible.
+ --BBI;
+ ++NumRedundantStores;
+ MadeChange = true;
+ };
+
if (LoadInst *DepLoad = dyn_cast<LoadInst>(SI->getValueOperand())) {
if (SI->getPointerOperand() == DepLoad->getPointerOperand() &&
isRemovable(SI) &&
DEBUG(dbgs() << "DSE: Remove Store Of Load from same pointer:\n "
<< "LOAD: " << *DepLoad << "\n STORE: " << *SI << '\n');
- // DeleteDeadInstruction can delete the current instruction. Save BBI
- // in case we need it.
- WeakVH NextInst(BBI);
+ RemoveDeadInstAndUpdateBBI(SI);
+ continue;
+ }
+ }
- DeleteDeadInstruction(SI, *MD, *TLI);
+ // Remove null stores into the calloc'ed objects
+ Constant *StoredConstant = dyn_cast<Constant>(SI->getValueOperand());
- if (!NextInst) // Next instruction deleted.
- BBI = BB.begin();
- else if (BBI != BB.begin()) // Revisit this instruction if possible.
- --BBI;
- ++NumRedundantStores;
- MadeChange = true;
+ if (StoredConstant && StoredConstant->isNullValue() &&
+ isRemovable(SI)) {
+ Instruction *UnderlyingPointer = dyn_cast<Instruction>(
+ GetUnderlyingObject(SI->getPointerOperand(), DL));
+
+ if (UnderlyingPointer && isCallocLikeFn(UnderlyingPointer, TLI) &&
+ MemoryIsNotModifiedBetween(UnderlyingPointer, SI)) {
+ DEBUG(dbgs()
+ << "DSE: Remove null store to the calloc'ed object:\n DEAD: "
+ << *Inst << "\n OBJECT: " << *UnderlyingPointer << '\n');
+
+ RemoveDeadInstAndUpdateBBI(SI);
continue;
}
}
if (isRemovable(DepWrite) &&
!isPossibleSelfRead(Inst, Loc, DepWrite, *TLI, *AA)) {
int64_t InstWriteOffset, DepWriteOffset;
- const DataLayout &DL = BB.getModule()->getDataLayout();
OverwriteResult OR =
isOverwrite(Loc, DepLoc, DL, *TLI, DepWriteOffset, InstWriteOffset);
if (OR == OverwriteComplete) {
return MadeChange;
}
-/// Returns true if the memory which is accessed by the store instruction is not
-/// modified between the load and the store instruction.
-/// Precondition: The store instruction must be dominated by the load
+/// Returns true if the memory which is accessed by the second instruction is not
+/// modified between the first and the second instruction.
+/// Precondition: Second instruction must be dominated by the first
/// instruction.
-bool DSE::MemoryIsNotModifiedBetween(LoadInst *LI, StoreInst *SI) {
+bool DSE::MemoryIsNotModifiedBetween(Instruction *FirstI,
+ Instruction *SecondI) {
SmallVector<BasicBlock *, 16> WorkList;
SmallPtrSet<BasicBlock *, 8> Visited;
- BasicBlock::iterator LoadBBI(LI);
- ++LoadBBI;
- BasicBlock::iterator StoreBBI(SI);
- BasicBlock *LoadBB = LI->getParent();
- BasicBlock *StoreBB = SI->getParent();
- MemoryLocation StoreLoc = MemoryLocation::get(SI);
+ BasicBlock::iterator FirstBBI(FirstI);
+ ++FirstBBI;
+ BasicBlock::iterator SecondBBI(SecondI);
+ BasicBlock *FirstBB = FirstI->getParent();
+ BasicBlock *SecondBB = SecondI->getParent();
+ MemoryLocation MemLoc = MemoryLocation::get(SecondI);
// Start checking the store-block.
- WorkList.push_back(StoreBB);
+ WorkList.push_back(SecondBB);
bool isFirstBlock = true;
// Check all blocks going backward until we reach the load-block.
while (!WorkList.empty()) {
BasicBlock *B = WorkList.pop_back_val();
- // Ignore instructions before LI if this is the LoadBB.
- BasicBlock::iterator BI = (B == LoadBB ? LoadBBI : B->begin());
+ // Ignore instructions before LI if this is the FirstBB.
+ BasicBlock::iterator BI = (B == FirstBB ? FirstBBI : B->begin());
BasicBlock::iterator EI;
if (isFirstBlock) {
- // Ignore instructions after SI if this is the first visit of StoreBB.
- assert(B == StoreBB && "first block is not the store block");
- EI = StoreBBI;
+ // Ignore instructions after SI if this is the first visit of SecondBB.
+ assert(B == SecondBB && "first block is not the store block");
+ EI = SecondBBI;
isFirstBlock = false;
} else {
- // It's not StoreBB or (in case of a loop) the second visit of StoreBB.
+ // It's not SecondBB or (in case of a loop) the second visit of SecondBB.
// In this case we also have to look at instructions after SI.
EI = B->end();
}
for (; BI != EI; ++BI) {
Instruction *I = BI;
- if (I->mayWriteToMemory() && I != SI) {
- auto Res = AA->getModRefInfo(I, StoreLoc);
+ if (I->mayWriteToMemory() && I != SecondI) {
+ auto Res = AA->getModRefInfo(I, MemLoc);
if (Res != MRI_NoModRef)
return false;
}
}
- if (B != LoadBB) {
- assert(B != &LoadBB->getParent()->getEntryBlock() &&
+ if (B != FirstBB) {
+ assert(B != &FirstBB->getParent()->getEntryBlock() &&
"Should not hit the entry block because SI must be dominated by LI");
for (auto PredI = pred_begin(B), PE = pred_end(B); PredI != PE; ++PredI) {
if (!Visited.insert(*PredI).second)
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