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[LegalizeVectorOps] Use getBoolConstant instead of getAllOnesConstant in VectorLegalizer::UnrollVSETCC. #121526

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Merged
merged 2 commits into from
Jan 3, 2025
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[LegalizeVectorOps] Use getBoolConstant instead of getAllOnesConstant in VectorLegalizer::UnrollVSETCC. #121526

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[LegalizeVectorOps] Use getBoolConstant instead of getAllOnesConstant…
topperc Jan 2, 2025
1573cfb
fixup! add FIXME.
topperc Jan 3, 2025
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4 changes: 3 additions & 1 deletion llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2246,11 +2246,13 @@ SDValue VectorLegalizer::UnrollVSETCC(SDNode *Node) {
DAG.getVectorIdxConstant(i, dl));
SDValue RHSElem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, TmpEltVT, RHS,
DAG.getVectorIdxConstant(i, dl));
// FIXME: We should use i1 setcc + boolext here, but it causes regressions.
Ops[i] = DAG.getNode(ISD::SETCC, dl,
TLI.getSetCCResultType(DAG.getDataLayout(),
*DAG.getContext(), TmpEltVT),
LHSElem, RHSElem, CC);
Ops[i] = DAG.getSelect(dl, EltVT, Ops[i], DAG.getAllOnesConstant(dl, EltVT),
Ops[i] = DAG.getSelect(dl, EltVT, Ops[i],
DAG.getBoolConstant(true, dl, EltVT, VT),
DAG.getConstant(0, dl, EltVT));
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I still think this should be:

    Ops[i] = DAG.getNode(ISD::SETCC, dl, MVT::i1, LHSElem, RHSElem, CC);
    Ops[i] = DAG.getBoolExtOrTrunc(Ops[i], dl, EltVT, VT);

But the last time I attempted this it resulted in a lot of churn: https://github.com/RKSimon/llvm-project/tree/unroll-setcc

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Thanks. I didn't know there was history here. Have any of the yaks been shaved yet?

Still seems like we should either fix the code with getBoolConstant or add a FIXME until we can use getBoolExtOrTrunc. That way the next person who reads this code doesn't think it's wrong like I just did.

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Agreed, a fixme comment would be acceptable for now.

}
return DAG.getBuildVector(VT, dl, Ops);
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