[llvm] [LV][EVL] Support in-loop reduction using tail folding with EVL. (PR #90184)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

The title mentions this adds support for in-loop reductions, but I wasn't able to find a check to make sure we only vectorize in-loop reductions?

All tests seem to pass flags guiding towards the use of in-loop/ordered reductions, so the case where the regular reduction strategy is chosen may not be tested well

https://github.com/llvm/llvm-project/pull/90184