ConstantFold: Zero-sized globals might land on top of another global
A zero sized array is zero sized and might share its address with
another global.
llvm-svn: 223684
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index 719a3a4..4cb22bc 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -1348,12 +1348,24 @@
static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
const GlobalValue *GV2) {
- auto isLinkageUnsafeForEquality = [](const GlobalValue *GV) {
- return GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage();
+ auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
+ if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage())
+ return true;
+ if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
+ Type *Ty = GVar->getType()->getPointerElementType();
+ // A global with opaque type might end up being zero sized.
+ if (!Ty->isSized())
+ return true;
+ // A global with an empty type might lie at the address of any other
+ // global.
+ if (Ty->isEmptyTy())
+ return true;
+ }
+ return false;
};
// Don't try to decide equality of aliases.
if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
- if (!isLinkageUnsafeForEquality(GV1) && !isLinkageUnsafeForEquality(GV2))
+ if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
return ICmpInst::ICMP_NE;
return ICmpInst::BAD_ICMP_PREDICATE;
}