[llvm] [LoopVectorizer] Add support for partial reductions (PR #92418)

[Graham Hunter via llvm-commits]

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@@ -2020,6 +2032,8 @@ class VPReductionPHIRecipe : public VPHeaderPHIRecipe {
     return R->getVPDefID() == VPDef::VPReductionPHISC;
   }
 
+  void SetVFScaleFactor(unsigned ScaleFactor) { VFScaleFactor = ScaleFactor; }
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huntergr-arm wrote:

This won't be needed if `postInsertionOp` is removed.

https://github.com/llvm/llvm-project/pull/92418