[llvm] [DAG] SDPatternMatch - Fix m_Reassociatable mismatching (PR #170061)

[Min-Yih Hsu via llvm-commits]

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@@ -842,6 +842,28 @@ TEST_F(SelectionDAGPatternMatchTest, matchReassociatableOp) {
   EXPECT_TRUE(sd_match(
       MUL, m_ReassociatableMul(m_Value(), m_Value(), m_Value(), m_Value())));
 
+  // (Op0 + Op1) + Op0 binds correctly, allowing commutation
+  SDValue ADD010 = DAG->getNode(ISD::ADD, DL, Int32VT, ADD01, Op0);
+  SDValue A, B;
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mshockwave wrote:

> because as it currently is, the matching commutes the leaf nodes and not the patterns,

Ah that makes sense to me. Then I think we should _not_ allow m_Value(A), m_Deferred(B), m_Value(B) to match. So on this end no change is needed.

https://github.com/llvm/llvm-project/pull/170061