[llvm] [VPlan] Sink retrieving legacy costs to more specific computeCost impls. (PR #109708)

[via llvm-commits]

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@@ -2326,6 +2332,9 @@ class VPInterleaveRecipe : public VPRecipeBase {
   /// Generate the wide load or store, and shuffles.
   void execute(VPTransformState &State) override;
 
+  InstructionCost computeCost(ElementCount VF,
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ayalz wrote:

Would be good to /// document, here and elsewhere.

https://github.com/llvm/llvm-project/pull/109708