[llvm] [LV] Add support for partial alias masking with tail folding (PR #182457)

[Sander de Smalen via llvm-commits]

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@@ -675,6 +675,12 @@ class LoopVectorizationPlanner {
   void attachRuntimeChecks(VPlan &Plan, GeneratedRTChecks &RTChecks,
                            bool HasBranchWeights) const;
 
+  /// Materializes the alias mask within a check block before the loop. The
+  /// vector loop will only be entered if the clamped VF from the alias mask
+  /// is not scalar.
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sdesmalen-arm wrote:

nit: (I find the 'scalar VF' terminology confusing)
```suggestion
  /// is larger than 1.
```

https://github.com/llvm/llvm-project/pull/182457