[llvm] [LV] Use VPReductionRecipe for partial reductions (PR #144908)

[Sander de Smalen via llvm-commits]

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@@ -2861,6 +2886,12 @@ tryToMatchAndCreateMulAccumulateReduction(VPReductionRecipe *Red,
 
   VPValue *VecOp = Red->getVecOp();
   VPValue *A, *B;
+  // Some chained partial reductions used for complex numbers will have a
+  // negation between the mul and reduction. This extracts the mul from that
+  // pattern to use it for further checking.
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sdesmalen-arm wrote:

nit: Instead of "Some chained partialr eductions used for complex numbers" you can just say 'sub reductions'?

https://github.com/llvm/llvm-project/pull/144908