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Make AliasAnalysis::getModRefInfo conservative in the face of volatility.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110120 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-08-03 17:27:43 +00:00
parent bae696956b
commit 14a498a486
1 changed files with 20 additions and 3 deletions
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23
lib/Analysis/AliasAnalysis.cpp
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@ -78,8 +78,17 @@ AliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
AliasAnalysis::ModRefResult
AliasAnalysis::getModRefInfo(LoadInst *L, Value *P, unsigned Size) {
return alias(L->getOperand(0), getTypeStoreSize(L->getType()),
P, Size) ? Ref : NoModRef;
// If the load address doesn't alias the given address, it doesn't read
// or write the specified memory.
if (!alias(L->getOperand(0), getTypeStoreSize(L->getType()), P, Size))
return NoModRef;
// Be conservative in the face of volatile.
if (L->isVolatile())
return ModRef;
// Otherwise, a load just reads.
return Ref;
}
AliasAnalysis::ModRefResult
@ -90,9 +99,17 @@ AliasAnalysis::getModRefInfo(StoreInst *S, Value *P, unsigned Size) {
getTypeStoreSize(S->getOperand(0)->getType()), P, Size))
return NoModRef;
// Be conservative in the face of volatile.
if (S->isVolatile())
return ModRef;
// If the pointer is a pointer to constant memory, then it could not have been
// modified by this store.
return pointsToConstantMemory(P) ? NoModRef : Mod;
if (pointsToConstantMemory(P))
return NoModRef;
// Otherwise, a store just writes.
return Mod;
}
AliasAnalysis::ModRefBehavior