[llvm] [SCEV] Simplify SCEVExpr for PHI to SCEV for operand if operands are identical (PR #115945)

[Yingwei Zheng via llvm-commits]

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@@ -6019,6 +6019,37 @@ const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
   return nullptr;
 }
 
+// Returns SCEV for the first operand of a phi if all phi operands have
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dtcxzyw wrote:

```suggestion
/// Returns SCEV for the first operand of a phi if all phi operands have
```
Use `///` for header comments.


https://github.com/llvm/llvm-project/pull/115945