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[X86] detectPMADDUBSW - use SDPatternMatch to handle some of the commutative matching for the zext/sext pairs. NFC. #165861

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Merged
merged 2 commits into from
Oct 31, 2025
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[X86] detectPMADDUBSW - use SDPatternMatch to handle some of the commutative matching for the zext/sext pairs. NFC. #165861

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[X86] detectPMADDUBSW - use SDPatternMatch to handle some of the comm…
RKSimon Oct 31, 2025
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RKSimon Oct 31, 2025
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40 changes: 9 additions & 31 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54459,6 +54459,7 @@ static SDValue combinePMULH(SDValue Src, EVT VT, const SDLoc &DL,
static SDValue detectPMADDUBSW(SDValue In, EVT VT, SelectionDAG &DAG,
const X86Subtarget &Subtarget,
const SDLoc &DL) {
using namespace SDPatternMatch;
if (!VT.isVector() || !Subtarget.hasSSSE3())
return SDValue();

Expand All @@ -54468,42 +54469,19 @@ static SDValue detectPMADDUBSW(SDValue In, EVT VT, SelectionDAG &DAG,
return SDValue();

SDValue SSatVal = detectSSatPattern(In, VT);
if (!SSatVal || SSatVal.getOpcode() != ISD::ADD)
return SDValue();

// Ok this is a signed saturation of an ADD. See if this ADD is adding pairs
// of multiplies from even/odd elements.
SDValue N0 = SSatVal.getOperand(0);
SDValue N1 = SSatVal.getOperand(1);

if (N0.getOpcode() != ISD::MUL || N1.getOpcode() != ISD::MUL)
if (!SSatVal)
return SDValue();

SDValue N00 = N0.getOperand(0);
SDValue N01 = N0.getOperand(1);
SDValue N10 = N1.getOperand(0);
SDValue N11 = N1.getOperand(1);

// See if this is a signed saturation of an ADD, adding pairs of multiplies
// from even/odd elements, from zero_extend/sign_extend operands.
//
// TODO: Handle constant vectors and use knownbits/computenumsignbits?
// Canonicalize zero_extend to LHS.
if (N01.getOpcode() == ISD::ZERO_EXTEND)
std::swap(N00, N01);
if (N11.getOpcode() == ISD::ZERO_EXTEND)
std::swap(N10, N11);

// Ensure we have a zero_extend and a sign_extend.
if (N00.getOpcode() != ISD::ZERO_EXTEND ||
N01.getOpcode() != ISD::SIGN_EXTEND ||
N10.getOpcode() != ISD::ZERO_EXTEND ||
N11.getOpcode() != ISD::SIGN_EXTEND)
SDValue N00, N01, N10, N11;
if (!sd_match(SSatVal,
m_Add(m_Mul(m_ZExt(m_Value(N00)), m_SExt(m_Value(N01))),
m_Mul(m_ZExt(m_Value(N10)), m_SExt(m_Value(N11))))))
return SDValue();

// Peek through the extends.
N00 = N00.getOperand(0);
N01 = N01.getOperand(0);
N10 = N10.getOperand(0);
N11 = N11.getOperand(0);

// Ensure the extend is from vXi8.
if (N00.getValueType().getVectorElementType() != MVT::i8 ||
N01.getValueType().getVectorElementType() != MVT::i8 ||
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