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

[Nikita Popov via llvm-commits]

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@@ -1761,6 +1761,10 @@ class ScalarEvolution {
   /// V.
   const SCEV *getOperandsToCreate(Value *V, SmallVectorImpl<Value *> &Ops);
 
+  /// Returns SCEV for the first operand of a phi if all phi operands have
+  /// identical opcodes and operands
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nikic wrote:

```suggestion
  /// identical opcodes and operands.
```

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