[llvm] Combine (X ^ Y) and (X == Y) where appropriate (PR #130922)

[Ryan Buchner via llvm-commits]

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@@ -8578,7 +8578,8 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI,
     }
     if (Cmp->isEquality() &&
         (match(UI, m_Add(m_Specific(X), m_SpecificInt(-CmpC))) ||
-         match(UI, m_Sub(m_Specific(X), m_SpecificInt(CmpC))))) {
+         match(UI, m_Sub(m_Specific(X), m_SpecificInt(CmpC))) ||
+         match(UI, m_Xor(m_Specific(X), m_SpecificInt(CmpC))))) {
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bababuck wrote:

Yes. There were two changes needed, first making sure the CodeGen shifts the `Xor` before the comparison (this change), and second imaking sure the RISCV backend doesn't fold the  `xor` back in with the comparison.

https://github.com/llvm/llvm-project/pull/130922