Don't assume that external global variables are aligned at their preferred
alignment. Only the minimum alignment guaranteed by the ABI may be assumed.
llvm-svn: 78668
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index dbaadd8..af86494 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -81,8 +81,16 @@
// 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));