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[DAG] visitTRUNCATE - merge the trunc(abd) and trunc(avg) handling which are almost identical (#154301)

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CC @houngkoungting
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Simon Pilgrim 2025-08-19 12:59:39 +01:00 committed by GitHub
parent df57bb8c49
commit fcb36ca8cc
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1 changed files with 9 additions and 37 deletions
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46
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -16279,40 +16279,6 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
// because targets may prefer a wider type during later combines and invert
// this transform.
switch (N0.getOpcode()) {
case ISD::AVGCEILU:
case ISD::AVGFLOORU:
if (!LegalOperations && N0.hasOneUse() &&
TLI.isOperationLegal(N0.getOpcode(), VT)) {
SDValue X = N0.getOperand(0);
SDValue Y = N0.getOperand(1);
unsigned SrcBits = X.getScalarValueSizeInBits();
unsigned DstBits = VT.getScalarSizeInBits();
APInt UpperBits = APInt::getBitsSetFrom(SrcBits, DstBits);
if (DAG.MaskedValueIsZero(X, UpperBits) &&
DAG.MaskedValueIsZero(Y, UpperBits)) {
SDValue Tx = DAG.getNode(ISD::TRUNCATE, DL, VT, X);
SDValue Ty = DAG.getNode(ISD::TRUNCATE, DL, VT, Y);
return DAG.getNode(N0.getOpcode(), DL, VT, Tx, Ty);
}
}
break;
case ISD::AVGCEILS:
case ISD::AVGFLOORS:
if (!LegalOperations && N0.hasOneUse() &&
TLI.isOperationLegal(N0.getOpcode(), VT)) {
SDValue X = N0.getOperand(0);
SDValue Y = N0.getOperand(1);
unsigned SrcBits = X.getScalarValueSizeInBits();
unsigned DstBits = VT.getScalarSizeInBits();
unsigned NeededSignBits = SrcBits - DstBits + 1;
if (DAG.ComputeNumSignBits(X) >= NeededSignBits &&
DAG.ComputeNumSignBits(Y) >= NeededSignBits) {
SDValue Tx = DAG.getNode(ISD::TRUNCATE, DL, VT, X);
SDValue Ty = DAG.getNode(ISD::TRUNCATE, DL, VT, Y);
return DAG.getNode(N0.getOpcode(), DL, VT, Tx, Ty);
}
}
break;
case ISD::ADD:
case ISD::SUB:
case ISD::MUL:
@ -16361,10 +16327,15 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
DAG, DL);
}
break;
case ISD::ABDU:
case ISD::AVGFLOORS:
case ISD::AVGFLOORU:
case ISD::AVGCEILS:
case ISD::AVGCEILU:
case ISD::ABDS:
case ISD::ABDU:
// (trunc (avg a, b)) -> (avg (trunc a), (trunc b))
// (trunc (abdu/abds a, b)) -> (abdu/abds (trunc a), (trunc b))
if ((!LegalOperations || N0.hasOneUse()) &&
if (!LegalOperations && N0.hasOneUse() &&
TLI.isOperationLegal(N0.getOpcode(), VT)) {
EVT TruncVT = VT;
unsigned SrcBits = SrcVT.getScalarSizeInBits();
@ -16374,7 +16345,8 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
SDValue B = N0.getOperand(1);
bool CanFold = false;
if (N0.getOpcode() == ISD::ABDU) {
if (N0.getOpcode() == ISD::AVGFLOORU || N0.getOpcode() == ISD::AVGCEILU ||
N0.getOpcode() == ISD::ABDU) {
APInt UpperBits = APInt::getBitsSetFrom(SrcBits, TruncBits);
CanFold = DAG.MaskedValueIsZero(B, UpperBits) &&
DAG.MaskedValueIsZero(A, UpperBits);