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DAG: Lower fcNormal is.fpclass to compare with inf #100389

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Oct 17, 2024
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DAG: Lower fcNormal is.fpclass to compare with inf #100389

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25 changes: 25 additions & 0 deletions llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8790,6 +8790,31 @@ SDValue TargetLowering::expandIS_FPCLASS(EVT ResultVT, SDValue Op,
IsOrdered ? OrderedOp : UnorderedOp);
}
}

if (FPTestMask == fcNormal) {
// TODO: Handle unordered
ISD::CondCode IsFiniteOp = IsInvertedFP ? ISD::SETUGE : ISD::SETOLT;
ISD::CondCode IsNormalOp = IsInvertedFP ? ISD::SETOLT : ISD::SETUGE;

if (isCondCodeLegalOrCustom(IsFiniteOp,
OperandVT.getScalarType().getSimpleVT()) &&
isCondCodeLegalOrCustom(IsNormalOp,
OperandVT.getScalarType().getSimpleVT()) &&
isFAbsFree(OperandVT)) {
// isnormal(x) --> fabs(x) < infinity && !(fabs(x) < smallest_normal)
SDValue Inf =
DAG.getConstantFP(APFloat::getInf(Semantics), DL, OperandVT);
SDValue SmallestNormal = DAG.getConstantFP(
APFloat::getSmallestNormalized(Semantics), DL, OperandVT);

SDValue Abs = DAG.getNode(ISD::FABS, DL, OperandVT, Op);
SDValue IsFinite = DAG.getSetCC(DL, ResultVT, Abs, Inf, IsFiniteOp);
SDValue IsNormal =
DAG.getSetCC(DL, ResultVT, Abs, SmallestNormal, IsNormalOp);
unsigned LogicOp = IsInvertedFP ? ISD::OR : ISD::AND;
return DAG.getNode(LogicOp, DL, ResultVT, IsFinite, IsNormal);
}
}
}

// Some checks may be represented as inversion of simpler check, for example
Expand Down