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

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Hi - Sounds like a nice approach.

> This patch only implements the pattern recognition and production of the partial reduction intrinsic, it does not yet lower the intrinsic to valid IR/Asm, those will be coming later.

They might need to come first, or at least be committed first. The intrinsics will need language ref which will need to be agreed upon, and some generic lowering.

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