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Realize the gep P, <zeros> must aliases P.

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This is a partial fix for PR 86


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10399 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-12-11 06:02:00 +00:00
parent 863914578a
commit 88d3e03429
1 changed files with 11 additions and 1 deletions
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12
lib/Analysis/BasicAliasAnalysis.cpp
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@ -175,12 +175,22 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
// If there is at least one non-zero constant index, we know they cannot
// alias.
bool ConstantFound = false;
bool AllZerosFound = true;
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i)))
if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i))) {
if (!C->isNullValue()) {
ConstantFound = true;
break;
}
} else {
AllZerosFound = false;
}
// If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
// the ptr, the end result is a must alias also.
if (AllZerosFound)
return MustAlias;
if (ConstantFound) {
if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
return NoAlias;