[llvm] InstCombine: fold(select C, (X | A), X) | B into X | select C, (A | B), B. (#154246) (PR #154267)

[Rohan A M via llvm-commits]

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@@ -2695,6 +2695,40 @@ Instruction *InstCombinerImpl::visitAnd(BinaryOperator &I) {
   if (Instruction *FoldedLogic = foldBinOpIntoSelectOrPhi(I))
     return FoldedLogic;
 
+  // Factor a common operand across select feeding an 'or':
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badwriter123 wrote:

Hello, 
while working on the optimization for the OR operation , I rewrite the expression from (select C, (X | A), X) | B to select C, (A | B),B. The same OR optimization can be used to rewrite AND operations as well. Instead of overengineering , I thought of duplicating it for AND operations.

if not required for AND operations, the code can be discarded.

https://github.com/llvm/llvm-project/pull/154267