[llvm] [VPlan] First step towards VPlan cost modeling (LegacyCM in CostCtx) (PR #92555)

[via llvm-commits]

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@@ -1621,6 +1622,12 @@ class LoopVectorizationCostModel {
   /// \p VF is the vectorization factor chosen for the original loop.
   bool isEpilogueVectorizationProfitable(const ElementCount VF) const;
 
+  /// Return the cost of instructions in an inloop reduction pattern, if I is
+  /// part of that pattern.
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ayalz wrote:

```suggestion
  /// Return the cost of instructions in an inloop reduction pattern, if \p I
  /// is part of that pattern.
```
(unrelated to this patch).

https://github.com/llvm/llvm-project/pull/92555