[llvm] [LV] Support tail-folded epilogue loops (PR #208764)

[Hassnaa Hamdi via llvm-commits]

================
@@ -856,6 +856,10 @@ class LoopVectorizationPlanner {
   /// The profitability analysis.
   LoopVectorizationCostModel &CM;
 
+  /// The profitability analysis for epilogue tail-folding.
+  /// Cleared after making cost based decisions.
+  std::unique_ptr<LoopVectorizationCostModel> EpilogueTfCM;
----------------
hassnaaHamdi wrote:

I thought about doing that, but I chose to follow the same design of letting the `processLoop` to construct the objects and pass it.
And storing the object in the planner will be needed anyway when the feature works for any VF.

https://github.com/llvm/llvm-project/pull/208764