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[SDAG] Harden assumption in getMemsetStringVal #126207

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Merged
merged 2 commits into from
Feb 13, 2025
Merged

[SDAG] Harden assumption in getMemsetStringVal #126207

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[SDAG] Harden assumption in getMemsetStringVal
c-rhodes Feb 6, 2025
2dfa6fe
address comments
c-rhodes Feb 10, 2025
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13 changes: 2 additions & 11 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8015,17 +8015,8 @@ static SDValue getMemsetStringVal(EVT VT, const SDLoc &dl, SelectionDAG &DAG,
if (Slice.Array == nullptr) {
if (VT.isInteger())
return DAG.getConstant(0, dl, VT);
if (VT == MVT::f32 || VT == MVT::f64 || VT == MVT::f128)
return DAG.getConstantFP(0.0, dl, VT);
if (VT.isVector()) {
unsigned NumElts = VT.getVectorNumElements();
MVT EltVT = (VT.getVectorElementType() == MVT::f32) ? MVT::i32 : MVT::i64;
return DAG.getNode(ISD::BITCAST, dl, VT,
DAG.getConstant(0, dl,
EVT::getVectorVT(*DAG.getContext(),
EltVT, NumElts)));
}
Comment on lines -8020 to -8027
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This can just bitcast to VT.changeVectorElementTypeToInteger?

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that would also work I guess, although it's not obvious to me that's any better than calling getConstantFP?

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I mean instead of having this unreachable case

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not sure if my understanding is correct, but I've updated to what I believe you're suggesting, except I've used changeTypeToInteger since it handles both scalar/vector.

llvm_unreachable("Expected type!");
return DAG.getNode(ISD::BITCAST, dl, VT,
DAG.getConstant(0, dl, VT.changeTypeToInteger()));
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Technically this can be used for the isInteger() path above as well, but I'm not sure if that just gets confusing?

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@c-rhodes c-rhodes Feb 10, 2025 •
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that crossed my mind also and is perhaps what @arsenm was referring to as well, I don't mind either way.

}

assert(!VT.isVector() && "Can't handle vector type here!");
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