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Don't assume that external global variables are aligned at their preferred

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alignment. Only the minimum alignment guaranteed by the ABI may be assumed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78668 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-08-11 15:50:03 +00:00
parent 00b0a243bd
commit 004072508b
2 changed files with 32 additions and 2 deletions
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12
lib/Analysis/ValueTracking.cpp
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@ -81,8 +81,16 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
// The address of an aligned GlobalValue has trailing zeros.
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD && GV->getType()->getElementType()->isSized())
Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) {
const Type *ObjectType = GV->getType()->getElementType();
// If the object is defined in the current Module, we'll be giving
// it the preferred alignment. Otherwise, we have to assume that it
// may only have the minimum ABI alignment.
if (!GV->isDeclaration() && !GV->mayBeOverridden())
Align = TD->getPrefTypeAlignment(ObjectType);
else
Align = TD->getABITypeAlignment(ObjectType);
}
if (Align > 0)
KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
CountTrailingZeros_32(Align));