[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[via llvm-commits]

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@@ -190,7 +190,10 @@ enum class TailFoldingStyle {
   /// Use predicate to control both data and control flow, but modify
   /// the trip count so that a runtime overflow check can be avoided
   /// and such that the scalar epilogue loop can always be removed.
-  DataAndControlFlowWithoutRuntimeCheck
+  DataAndControlFlowWithoutRuntimeCheck,
+  /// Use predicated EVL instructions for tail-folding.
+  /// Indicates that VP intrinsics should be used if tail-folding is enabled.
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ayalz wrote:

The suffix "if tail-folding is enabled" seems redundant - if it's not enabled the choice should be `None` rather than `DataWithEVL`?

https://github.com/llvm/llvm-project/pull/76172