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[DAG] Implement SDPatternMatch m_Abs() matcher #144512

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Merged
merged 2 commits into from
Jun 18, 2025
Merged

[DAG] Implement SDPatternMatch m_Abs() matcher #144512

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44570bc
[DAG] Implement SDPatternMatch `m_Abs()` matcher
Rajveer100 Jun 17, 2025
12128cc
Merge branch 'main' into dag-sd-pattern-abs
RKSimon Jun 18, 2025
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4 changes: 4 additions & 0 deletions llvm/include/llvm/CodeGen/SDPatternMatch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -938,6 +938,10 @@ template <typename Opnd> inline UnaryOpc_match<Opnd> m_Trunc(const Opnd &Op) {
return UnaryOpc_match<Opnd>(ISD::TRUNCATE, Op);
}

template <typename Opnd> inline UnaryOpc_match<Opnd> m_Abs(const Opnd &Op) {
return UnaryOpc_match<Opnd>(ISD::ABS, Op);
}

/// Match a zext or identity
/// Allows to peek through optional extensions
template <typename Opnd> inline auto m_ZExtOrSelf(const Opnd &Op) {
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12 changes: 3 additions & 9 deletions llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Expand Up @@ -11260,19 +11260,13 @@ SDValue DAGCombiner::foldABSToABD(SDNode *N, const SDLoc &DL) {
if (N->getOpcode() == ISD::TRUNCATE)
N = N->getOperand(0).getNode();

if (N->getOpcode() != ISD::ABS)
return SDValue();

EVT VT = N->getValueType(0);
SDValue AbsOp1 = N->getOperand(0);
SDValue Op0, Op1;

if (AbsOp1.getOpcode() != ISD::SUB)
if (!sd_match(N, m_Abs(m_Sub(m_Value(Op0), m_Value(Op1)))))
return SDValue();

Op0 = AbsOp1.getOperand(0);
Op1 = AbsOp1.getOperand(1);

SDValue AbsOp0 = N->getOperand(0);
unsigned Opc0 = Op0.getOpcode();

// Check if the operands of the sub are (zero|sign)-extended.
Expand All @@ -11282,7 +11276,7 @@ SDValue DAGCombiner::foldABSToABD(SDNode *N, const SDLoc &DL) {
Opc0 != ISD::SIGN_EXTEND_INREG)) {
// fold (abs (sub nsw x, y)) -> abds(x, y)
// Don't fold this for unsupported types as we lose the NSW handling.
if (AbsOp1->getFlags().hasNoSignedWrap() && hasOperation(ISD::ABDS, VT) &&
if (AbsOp0->getFlags().hasNoSignedWrap() && hasOperation(ISD::ABDS, VT) &&
TLI.preferABDSToABSWithNSW(VT)) {
SDValue ABD = DAG.getNode(ISD::ABDS, DL, VT, Op0, Op1);
return DAG.getZExtOrTrunc(ABD, DL, SrcVT);
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4 changes: 4 additions & 0 deletions llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
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Expand Up @@ -388,6 +388,8 @@ TEST_F(SelectionDAGPatternMatchTest, matchUnaryOp) {
SDValue SExt = DAG->getNode(ISD::SIGN_EXTEND, DL, Int64VT, Op0);
SDValue Trunc = DAG->getNode(ISD::TRUNCATE, DL, Int32VT, Op1);

SDValue Abs = DAG->getNode(ISD::ABS, DL, Int32VT, Op0);

SDValue Sub = DAG->getNode(ISD::SUB, DL, Int32VT, Trunc, Op0);
SDValue Neg = DAG->getNegative(Op0, DL, Int32VT);
SDValue Not = DAG->getNOT(DL, Op0, Int32VT);
Expand Down Expand Up @@ -417,6 +419,8 @@ TEST_F(SelectionDAGPatternMatchTest, matchUnaryOp) {
EXPECT_FALSE(sd_match(ZExt, m_SExtLike(m_Value())));
EXPECT_TRUE(sd_match(Trunc, m_Trunc(m_Specific(Op1))));

EXPECT_TRUE(sd_match(Abs, m_Abs(m_Specific(Op0))));

EXPECT_TRUE(sd_match(Neg, m_Neg(m_Value())));
EXPECT_TRUE(sd_match(Not, m_Not(m_Value())));
EXPECT_FALSE(sd_match(ZExt, m_Neg(m_Value())));
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