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[SelectionDAG] Fold (avg x, 0) -> x >> 1 #85581

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[SelectionDAG] Fold (avg x, 0) -> x >> 1 #85581

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8 changes: 7 additions & 1 deletion llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5135,7 +5135,13 @@ SDValue DAGCombiner::visitAVG(SDNode *N) {
if (N0 == N1 && Level >= AfterLegalizeTypes)
return N0;

// TODO If we use avg for scalars anywhere, we can add (avgfl x, 0) -> x >> 1
// fold (avgfloor x, 0) -> x >> 1
if (isNullOrNullSplat(N1)) {
if (Opcode == ISD::AVGFLOORS)
return DAG.getNode(ISD::SRA, DL, VT, N0, DAG.getConstant(1, DL, VT));
if (Opcode == ISD::AVGFLOORU)
return DAG.getNode(ISD::SRL, DL, VT, N0, DAG.getConstant(1, DL, VT));
}
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Remove the vector folds above? (github won't let me put this comment there)


return SDValue();
}
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