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

[Sam Tebbs via llvm-commits]

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@@ -2098,23 +2099,30 @@ class VPReductionPHIRecipe : public VPHeaderPHIRecipe {
   /// The phi is part of an ordered reduction. Requires IsInLoop to be true.
   bool IsOrdered;
 
+  /// The scaling difference between the size of the output of the entire
+  /// reduction and the size of the inputs When expanding the reduction PHI, the
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SamTebbs33 wrote:

The formatter messed this comment up. Fixed now.

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