[llvm] [InstCombine] simplify average of lsb (PR #95684)

[Yingwei Zheng via llvm-commits]

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@@ -1284,6 +1284,13 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
     return NewSub;
   }
 
+  // Fold (X + Y) / 2 --> (X & Y) iff (X u<= 1) && (Y u<= 1)
+  if (match(Op0, m_Add(m_Value(X), m_Value(Y))) && match(Op1, m_One()) &&
+      computeKnownBits(X, 0, &I).countMaxActiveBits() <= 1 &&
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dtcxzyw wrote:

http://llvm-compile-time-tracker.com/compare.php?from=d442bf043537fd4bc0c2fc5a4d77337b0d482ea9&to=8fda4ae9c656cec3a12a04a0a218149aac28eddf&stat=instructions:u


https://github.com/llvm/llvm-project/pull/95684