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optimize is_finite assembly #169402

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optimize is_finite assembly #169402

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11 changes: 9 additions & 2 deletions llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9122,8 +9122,15 @@ SDValue TargetLowering::expandIS_FPCLASS(EVT ResultVT, SDValue Op,
; // Detect finite numbers of f80 by checking individual classes because
// they have different settings of the explicit integer bit.
else if ((Test & fcFinite) == fcFinite) {
// finite(V) ==> abs(V) < exp_mask
PartialRes = DAG.getSetCC(DL, ResultVT, AbsV, ExpMaskV, ISD::SETLT);
// finite(V) ==> (a << 1) < (inf << 1)
//
// See https://github.com/llvm/llvm-project/issues/169270, this is slightly
// shorter than the `finite(V) ==> abs(V) < exp_mask` formula used before.
SDValue One = DAG.getShiftAmountConstant(1, IntVT, DL);
SDValue TwiceOp = DAG.getNode(ISD::SHL, DL, IntVT, OpAsInt, One);
SDValue TwiceInf = DAG.getNode(ISD::SHL, DL, IntVT, ExpMaskV, One);

PartialRes = DAG.getSetCC(DL, ResultVT, TwiceOp, TwiceInf, ISD::SETULT);
Test &= ~fcFinite;
} else if ((Test & fcFinite) == fcPosFinite) {
// finite(V) && V > 0 ==> V < exp_mask
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