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

[Florian Hahn via llvm-commits]

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@@ -22,6 +22,25 @@ class LoopVectorizationLegality;
 class LoopVectorizationCostModel;
 class TargetLibraryInfo;
 struct HistogramInfo;
+class TargetTransformInfo;
+
+/// A chain of instructions that form a partial reduction.
+/// Designed to match: reduction_bin_op (bin_op (extend (A), (extend (B))),
+/// accumulator)
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fhahn wrote:

nit: ```suggestion
/// accumulator).
```

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