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When promoting an alloca to registers discard any lifetime intrinsics.

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llvm-svn: 133251
This commit is contained in:
Nick Lewycky 2011-06-17 10:09:00 +00:00
parent 20552cda1a
commit 9bfe06b4d6
1 changed files with 59 additions and 0 deletions
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59
lib/Transforms/Utils/PromoteMemoryToRegister.cpp
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@ -73,6 +73,22 @@ struct DenseMapInfo<std::pair<BasicBlock*, unsigned> > {
};
}
/// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
/// are lifetime markers.
///
static bool onlyUsedByLifetimeMarkers(const Value *V) {
for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
UI != UE; ++UI) {
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(*UI);
if (!II) return false;
if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
II->getIntrinsicID() != Intrinsic::lifetime_end)
return false;
}
return true;
}
/// isAllocaPromotable - Return true if this alloca is legal for promotion.
/// This is true if there are only loads and stores to the alloca.
///
@ -92,6 +108,22 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) {
return false; // Don't allow a store OF the AI, only INTO the AI.
if (SI->isVolatile())
return false;
} else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
II->getIntrinsicID() != Intrinsic::lifetime_end)
return false;
} else if (const BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
if (BCI->getType() != Type::getInt8PtrTy(U->getContext()))
return false;
if (!onlyUsedByLifetimeMarkers(BCI))
return false;
} else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
if (GEPI->getType() != Type::getInt8PtrTy(U->getContext()))
return false;
if (!GEPI->hasAllZeroIndices())
return false;
if (!onlyUsedByLifetimeMarkers(GEPI))
return false;
} else {
return false;
}
@ -335,6 +367,31 @@ namespace {
};
} // end of anonymous namespace
static void removeLifetimeIntrinsicUsers(AllocaInst *AI) {
// Knowing that this alloca is promotable, we know that it's safe to kill all
// instructions except for load and store.
for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
UI != UE;) {
Instruction *I = cast<Instruction>(*UI);
++UI;
if (isa<LoadInst>(I) || isa<StoreInst>(I))
continue;
if (!I->getType()->isVoidTy()) {
// The only users of this bitcast/GEP instruction are lifetime intrinsics.
// Follow the use/def chain to erase them now instead of leaving it for
// dead code elimination later.
for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE;) {
Instruction *Inst = cast<Instruction>(*UI);
++UI;
Inst->eraseFromParent();
}
}
I->eraseFromParent();
}
}
void PromoteMem2Reg::run() {
Function &F = *DT.getRoot()->getParent();
@ -353,6 +410,8 @@ void PromoteMem2Reg::run() {
assert(AI->getParent()->getParent() == &F &&
"All allocas should be in the same function, which is same as DF!");
removeLifetimeIntrinsicUsers(AI);
if (AI->use_empty()) {
// If there are no uses of the alloca, just delete it now.
if (AST) AST->deleteValue(AI);