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[SCEV] Take global variable linkage into account when comparing values #148071

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Merged
merged 2 commits into from
Jul 11, 2025
Merged

[SCEV] Take global variable linkage into account when comparing values #148071

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[SCEV] Take global variable linkage into account
aeubanks Jul 10, 2025
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aeubanks Jul 11, 2025
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3 changes: 3 additions & 0 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Expand Up @@ -601,6 +601,9 @@ static int CompareValueComplexity(const LoopInfo *const LI, Value *LV,
if (const auto *LGV = dyn_cast<GlobalValue>(LV)) {
const auto *RGV = cast<GlobalValue>(RV);

if (auto L = LGV->getLinkage() - RGV->getLinkage())
return L;

const auto IsGVNameSemantic = [&](const GlobalValue *GV) {
auto LT = GV->getLinkage();
return !(GlobalValue::isPrivateLinkage(LT) ||
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30 changes: 30 additions & 0 deletions llvm/unittests/Analysis/ScalarEvolutionTest.cpp
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Expand Up @@ -1738,4 +1738,34 @@ TEST_F(ScalarEvolutionsTest, ComplexityComparatorIsStrictWeakOrdering2) {
SE.getAddExpr(Ops);
}

TEST_F(ScalarEvolutionsTest, ComplexityComparatorIsStrictWeakOrdering3) {
Type *Int64Ty = Type::getInt64Ty(Context);
Constant *Init = Constant::getNullValue(Int64Ty);
Type *PtrTy = PointerType::get(Context, 0);
Constant *Null = Constant::getNullValue(PtrTy);
FunctionType *FTy = FunctionType::get(Type::getVoidTy(Context), {}, false);

Value *V0 = new GlobalVariable(M, Int64Ty, false,
GlobalValue::ExternalLinkage, Init, "V0");
Value *V1 = new GlobalVariable(M, Int64Ty, false,
GlobalValue::ExternalLinkage, Init, "V1");
Value *V2 = new GlobalVariable(M, Int64Ty, false,
GlobalValue::InternalLinkage, Init, "V2");
Function *F = Function::Create(FTy, Function::ExternalLinkage, "f", M);
BasicBlock *BB = BasicBlock::Create(Context, "entry", F);
Value *C0 = ICmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ, V0, Null,
"c0", BB);
Value *C1 = ICmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ, V1, Null,
"c1", BB);
Value *C2 = ICmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ, V2, Null,
"c2", BB);
Value *Or0 = BinaryOperator::CreateOr(C0, C1, "or0", BB);
Value *Or1 = BinaryOperator::CreateOr(Or0, C2, "or1", BB);
ReturnInst::Create(Context, nullptr, BB);
ScalarEvolution SE = buildSE(*F);
// When _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG, this will
// crash if the comparator is inconsistent about global variable linkage.
SE.getSCEV(Or1);
}

} // end namespace llvm
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