[llvm] [IR][LangRef] Add partial reduction add intrinsic (PR #94499)

[via llvm-commits]

NickGuy-Arm wrote:

I've updated the langref, addressing the comments left. However I have not yet modified the codegen. 


> > What's the benefit to claiming this is a separate operation from the existing reduction intrinsics? Can't you just loosen the type declaration to allow vector types for the result?
> 
> ping?

Apologies @arsenm, I missed your message initially.
That would be the ideal result, yes; however at the moment it's useful, until feature parity is achieved, to keep this intrinsic in the experimental namespace. I believe Paul alluded to this further up, but the end goal is to migrate uses of reductions to use this over time, rather than attempting to retrofit vector->vector reductions into the existing reduction intrinsics.

https://github.com/llvm/llvm-project/pull/94499