[llvm] [LoopVectorize] Fix double-application of FindIV reduction expression in epilogue (PR #219362)

[Florian Hahn via llvm-commits]

================
@@ -2879,6 +2879,11 @@ class VPReductionPHIRecipe : public VPHeaderPHIRecipe, public VPIRFlags {
   /// compare has multiple uses.
   bool HasUsesOutsideReductionChain;
 
+  // True if FindIV's expression was sunk into the vector loop. Epilogue
+  // is disabled while this is true. Temporary until epilogue handles sunk
+  // expressions.
----------------
fhahn wrote:

```suggestion
  /// True if FindIV's expression was sunk into the vector loop. Epilogue
  /// is disabled while this is true. Temporary until epilogue handles sunk
  /// expressions.
```

https://github.com/llvm/llvm-project/pull/219362