llvm/llvm-project
Wrong types checked at DAGCombiner::visitSRA(SDNode *N)
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#153,543 opened on 2025/08/14
good first issuellvm:SelectionDAG
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説明
The following check is performed at DAGCombiner::visitSRA(SDNode *N)
if ((ShiftAmt > 0) &&
TLI.isOperationLegalOrCustom(ISD::SIGN_EXTEND, **TruncVT**) &&
TLI.isOperationLegalOrCustom(ISD::TRUNCATE, **VT**) &&
TLI.isTruncateFree(VT, TruncVT)) {
SDValue Amt = DAG.getShiftAmountConstant(ShiftAmt, VT, DL);
SDValue Shift = DAG.getNode(ISD::SRL, DL, VT,
N0.getOperand(0), Amt);
SDValue Trunc = DAG.getNode(ISD::TRUNCATE, DL, TruncVT,
Shift);
return DAG.getNode(ISD::SIGN_EXTEND, DL,
N->getValueType(0), Trunc);
}
but it should be
if ((ShiftAmt > 0) &&
TLI.isOperationLegalOrCustom(ISD::SIGN_EXTEND, **VT**) &&
TLI.isOperationLegalOrCustom(ISD::TRUNCATE, **TruncVT**) &&
TLI.isTruncateFree(VT, TruncVT)) {
SDValue Amt = DAG.getShiftAmountConstant(ShiftAmt, VT, DL);
SDValue Shift = DAG.getNode(ISD::SRL, DL, VT,
N0.getOperand(0), Amt);
SDValue Trunc = DAG.getNode(ISD::TRUNCATE, DL, TruncVT,
Shift);
return DAG.getNode(ISD::SIGN_EXTEND, DL,
N->getValueType(0), Trunc);
}
this mistake can cause operation marked with expand to reach selection