[llvm] [VPlan] Introduce CSE pass (PR #151872)

[Florian Hahn via llvm-commits]

================
@@ -286,6 +286,9 @@ struct VPlanTransforms {
   /// removing dead edges to their successors.
   static void removeBranchOnConst(VPlan &Plan);
 
+  /// Perform common-subexpression-elimination.
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fhahn wrote:

```suggestion
  /// Perform common-subexpression-elimination on \p Plan.
```

https://github.com/llvm/llvm-project/pull/151872