[llvm] [LV][NFC]Preselect folding style before choosing maxing VF, NFC. (PR #81885)

[Florian Hahn via llvm-commits]

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@@ -1509,15 +1509,25 @@ class LoopVectorizationCostModel {
   }
 
   /// Returns the TailFoldingStyle that is best for the current loop.
-  TailFoldingStyle
-  getTailFoldingStyle(bool IVUpdateMayOverflow = true) const {
-    if (!CanFoldTailByMasking)
-      return TailFoldingStyle::None;
+  TailFoldingStyle getTailFoldingStyle(bool IVUpdateMayOverflow = true) const {
+    return IVUpdateMayOverflow ? ChosenTailFoldingStyle.first
+                               : ChosenTailFoldingStyle.second;
+  }
+
+  void selectTailFoldinStyle() {
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fhahn wrote:

could you add some documentation here?

https://github.com/llvm/llvm-project/pull/81885