[SelectionDAG] Add m_Neg and m_Not pattern matcher and update DAGCombiner

[ZiCong-Wang]

Resolves #85065

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@llvm/pr-subscribers-llvm-selectiondag

Author: zicwangupa (ZiCong-Wang)

Changes

Resolves #85065

---

Full diff: https://github.com/llvm/llvm-project/pull/85365.diff

3 Files Affected:

• (modified) llvm/include/llvm/CodeGen/SDPatternMatch.h (+14)
• (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+3-3)
• (modified) llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp (+8)

diff --git a/llvm/include/llvm/CodeGen/SDPatternMatch.h b/llvm/include/llvm/CodeGen/SDPatternMatch.h
index a86c7400fa0945..2a475651b58a17 100644
--- a/llvm/include/llvm/CodeGen/SDPatternMatch.h
+++ b/llvm/include/llvm/CodeGen/SDPatternMatch.h
@@ -705,6 +705,20 @@ inline auto m_False() {
       },
       m_Value()};
 }
+
+/// Match a negtive as a sub(0, v)
+template <typename ValTy>
+inline BinaryOpc_match<SpecificInt_match, ValTy>
+m_Neg(const ValTy &V) {
+  return m_Sub(m_Zero(), V);
+}
+
+/// Match a Not as a xor(v, 1) or xor(1, v)
+template <typename ValTy>
+inline BinaryOpc_match<SpecificInt_match, ValTy, true>
+m_Not(const ValTy &V) {
+  return m_Xor(m_AllOnes(), V);
+}
 } // namespace SDPatternMatch
 } // namespace llvm
 #endif
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 40b078a201ace6..df084b86087c32 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2703,11 +2703,11 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
   SDValue A, B, C;
 
   // fold ((0-A) + B) -> B-A
-  if (sd_match(N0, m_Sub(m_Zero(), m_Value(A))))
+  if (sd_match(N0, m_Neg(m_Value(A))))
     return DAG.getNode(ISD::SUB, DL, VT, N1, A);
 
   // fold (A + (0-B)) -> A-B
-  if (sd_match(N1, m_Sub(m_Zero(), m_Value(B))))
+  if (sd_match(N1, m_Neg(m_Value(B))))
     return DAG.getNode(ISD::SUB, DL, VT, N0, B);
 
   // fold (A+(B-A)) -> B
@@ -3812,7 +3812,7 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
     return DAG.getNode(ISD::AND, DL, VT, N0, DAG.getNOT(DL, B, VT));
 
   // fold (A - (-B * C)) -> (A + (B * C))
-  if (sd_match(N1, m_OneUse(m_Mul(m_Sub(m_Zero(), m_Value(B)), m_Value(C)))))
+  if (sd_match(N1, m_OneUse(m_Mul(m_Neg(m_Value(B)), m_Value(C)))))
     return DAG.getNode(ISD::ADD, DL, VT, N0,
                        DAG.getNode(ISD::MUL, DL, VT, B, C));
 
diff --git a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
index 2b764c9e1f0fd6..372431f3080c8c 100644
--- a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
+++ b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
@@ -174,10 +174,18 @@ TEST_F(SelectionDAGPatternMatchTest, matchUnaryOp) {
   SDValue SExt = DAG->getNode(ISD::SIGN_EXTEND, DL, Int64VT, Op0);
   SDValue Trunc = DAG->getNode(ISD::TRUNCATE, DL, Int32VT, Op1);
 
+  SDValue Zero = DAG->getConstant(0, DL, Int32VT);
+  SDValue AllOnes = DAG->getConstant(APInt::getAllOnes(32), DL, Int32VT);
+  SDValue Neg = DAG->getNode(ISD::SUB, DL, Int32VT, Zero, Op0);
+  SDValue Not = DAG->getNode(ISD::XOR, DL, Int32VT, AllOnes, Op0);
+
   using namespace SDPatternMatch;
   EXPECT_TRUE(sd_match(ZExt, m_UnaryOp(ISD::ZERO_EXTEND, m_Value())));
   EXPECT_TRUE(sd_match(SExt, m_SExt(m_Value())));
   EXPECT_TRUE(sd_match(Trunc, m_Trunc(m_Specific(Op1))));
+
+  EXPECT_TRUE(sd_match(Neg, m_Neg(m_Value())));
+  EXPECT_TRUE(sd_match(Not, m_Not(m_Value())));
 }
 
 TEST_F(SelectionDAGPatternMatchTest, matchConstants) {

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[arsenm]

This should try matching the constant in the RHS operand, as that's canonical.

The IR pattern matchers have separate _c versions for versions that try to commute the inputs

[github-actions]

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