[llvm] [ExpandReductions] Add support for non-pow2 vector counts (PR #208738)

[Nikita Popov via llvm-commits]

nikic wrote:

I'm a bit unclear on why we're doing this. ExpandReductions is a legacy mechanism that has been superseded by VECREDUCE. Anything using ExpandReductions should be migrating to use VECREDUCE instead. So I'm not sure it really makes sense to expand the scope of ExpandReductions at this point?

https://github.com/llvm/llvm-project/pull/208738