[llvm] [VPlan] Impl VPlan-based pattern match for ExtendedRed and MulAccRed (NFCI) (PR #113903)

[Florian Hahn via llvm-commits]

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@@ -2694,6 +2724,202 @@ class VPReductionEVLRecipe : public VPReductionRecipe {
   }
 };
 
+/// A recipe to represent inloop extended reduction operations, performing a
+/// reduction on a vector operand into a scalar value, and adding the result to
+/// a chain. This recipe is high level abstract which will generate
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fhahn wrote:

```suggestion
/// a chain. This recipe is abstract and needs to be lowered to concrete recipes before codegen.
```

https://github.com/llvm/llvm-project/pull/113903