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[LegalizeDAG] PromoteNode FABS: Override promotion with clear sign bit #106076

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[LegalizeDAG] PromoteNode FABS: Override promotion with clear sign bit #106076

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22 changes: 21 additions & 1 deletion llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5576,6 +5576,27 @@ void SelectionDAGLegalize::PromoteNode(SDNode *Node) {
Results.push_back(Tmp2.getValue(1));
break;
}
case ISD::FABS: {
// if we can convert to a same sized int value, we bitcast to it,
// clear the sign bit and bitcast back to the original type.
EVT IntVT = OVT.changeTypeToInteger();
if (TLI.isTypeLegal(IntVT)) {
SDValue Cast = DAG.getNode(ISD::BITCAST, dl, IntVT, Node->getOperand(0));

APInt SignMask = APInt::getSignMask(IntVT.getScalarSizeInBits());

// Mask = ~(1 << (Size-1))
SDValue Mask = DAG.getConstant(SignMask, dl, IntVT);

SDValue And = DAG.getNode(ISD::AND, dl, IntVT, Cast, Mask);

SDValue Result = DAG.getNode(ISD::BITCAST, dl, OVT, And);
Results.push_back(Result);
break;
}

[[fallthrough]];
}
case ISD::FFLOOR:
case ISD::FCEIL:
case ISD::FRINT:
Expand All @@ -5597,7 +5618,6 @@ void SelectionDAGLegalize::PromoteNode(SDNode *Node) {
case ISD::FLOG:
case ISD::FLOG2:
case ISD::FLOG10:
case ISD::FABS:
case ISD::FEXP:
case ISD::FEXP2:
case ISD::FEXP10:
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