[llvm] [LV] Use VPReductionRecipe for partial reductions (PR #147513)

[Florian Hahn via llvm-commits]

================
@@ -2370,6 +2370,23 @@ struct VPFirstOrderRecurrencePHIRecipe : public VPHeaderPHIRecipe {
 #endif
 };
 
+// Possible variants of a reduction.
+
+// This reduction is ordered and in-loop.
+struct RdxOrderedInLoop {};
+// This reduction is in-loop.
+struct RdxInLoop {};
+// This reduction isn't partial, ordered or in-loop.
+struct RdxNormal {};
----------------
fhahn wrote:

IIRC VPReductionRecipe was introduced because there were no suitable intrinsics at that time. The variants that map directly to an intrinsic should not need a dedicated recipe at all down the line, as we can just generate the appropriate intrinsic directly

https://github.com/llvm/llvm-project/pull/147513