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ConstantFold: Don't optimize comparisons with weak linkage objects

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Consider:
void f() {}
void __attribute__((weak)) g() {}
bool b = &f != &g;

It's possble for g to resolve to f if --defsym=g=f is passed on to the
linker.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223585 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-12-06 11:58:33 +00:00
parent d34c5a921f
commit 278bbacd27
2 changed files with 9 additions and 1 deletions
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5
lib/IR/ConstantFold.cpp
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@@ -1348,9 +1348,12 @@ static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
const GlobalValue *GV2) {
auto isLinkageUnsafeForEquality = [](const GlobalValue *GV) {
return GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage();
};
// Don't try to decide equality of aliases.
if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
if (!GV1->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
if (!isLinkageUnsafeForEquality(GV1) && !isLinkageUnsafeForEquality(GV2))
return ICmpInst::ICMP_NE;
return ICmpInst::BAD_ICMP_PREDICATE;
}