[llvm] [InstCombine] Resolve FIXME: Use commutative matchers (PR #81060)

[Craig Topper via llvm-commits]

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@@ -2255,7 +2255,7 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
     // This is done in other passes, but we want to be able to consume this
     // pattern in InstCombine so we can generate it without creating infinite
     // loops.
-    if (match(Op0, m_Add(m_Value(X), m_Value(Z))) &&
+    if (match(Op0, m_c_Add(m_Value(X), m_Value(Z))) &&
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topperc wrote:

It doesn't matter. The `match` function in m_Value always returns true, so the m_Add will be satisfied on the first operand order it tries. It won't ever try the commuted order.

https://github.com/llvm/llvm-project/pull/81060