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

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for all the updates. A few more comments, then I think it should be good to go.

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