[llvm] [InstCombine] Fold ((X << nuw Z) binop nuw Y) >>u Z --> X binop nuw (Y >>u Z) (PR #88193)

[Yingwei Zheng via llvm-commits]

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@@ -1259,6 +1259,53 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
       match(Op1, m_SpecificIntAllowPoison(BitWidth - 1)))
     return new ZExtInst(Builder.CreateIsNotNeg(X, "isnotneg"), Ty);
 
+  // ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub nuw (Y >>u exact Z),
+  // ONLY if I is exact, and both the shift and sub are nuw
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dtcxzyw wrote:

```suggestion
```
It is the same as the above line.

https://github.com/llvm/llvm-project/pull/88193