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

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for the latest updates! A few more mostly minor comments inline.

It looks like the current patch needs to be updated on top of current `main`, would be good to do so for a final look. I don't expect many conflicts/issues, but IIRC ::computeCost now needs to be provided.

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