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[Constant] Make Constant::getSplatValue return poison on poison #141870

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Merged
merged 2 commits into from
May 29, 2025
Merged

[Constant] Make Constant::getSplatValue return poison on poison #141870

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f2f2997
[Constant] Make Constant::getSplatValue return poison on poison
lukel97 May 28, 2025
0eb5333
Mark undef/poison as non-constant in getOperandInfo to preserve exist…
lukel97 May 29, 2025
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5 changes: 0 additions & 5 deletions llvm/lib/Analysis/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3794,11 +3794,6 @@ static Constant *ConstantFoldScalableVectorCall(
SplatOps.push_back(Op);
continue;
}
// TODO: Should getSplatValue return a poison scalar for a poison vector?
if (isa<PoisonValue>(Op)) {
SplatOps.push_back(PoisonValue::get(Op->getType()->getScalarType()));
continue;
}
Constant *Splat = Op->getSplatValue();
if (!Splat)
return nullptr;
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4 changes: 4 additions & 0 deletions llvm/lib/Analysis/TargetTransformInfo.cpp
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Expand Up @@ -886,6 +886,10 @@ TargetTransformInfo::getOperandInfo(const Value *V) {
OperandValueKind OpInfo = OK_AnyValue;
OperandValueProperties OpProps = OP_None;

// undef/poison don't materialize constants.
if (isa<UndefValue>(V))
return {OK_AnyValue, OP_None};

if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) {
if (const auto *CI = dyn_cast<ConstantInt>(V)) {
if (CI->getValue().isPowerOf2())
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2 changes: 2 additions & 0 deletions llvm/lib/IR/Constants.cpp
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Expand Up @@ -1711,6 +1711,8 @@ void ConstantVector::destroyConstantImpl() {

Constant *Constant::getSplatValue(bool AllowPoison) const {
assert(this->getType()->isVectorTy() && "Only valid for vectors!");
if (isa<PoisonValue>(this))
return PoisonValue::get(cast<VectorType>(getType())->getElementType());
if (isa<ConstantAggregateZero>(this))
return getNullValue(cast<VectorType>(getType())->getElementType());
if (auto *CI = dyn_cast<ConstantInt>(this))
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