[llvm] [LV] Optionally preserve uniform branches when vectorizing (PR #128187)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for sharing the patch.

I am working on a few pending cleanups to initial VPlan construction that would be good to land first, including a cleaner separation of initial VPlan creation, predication and widened recipe creation.

There's https://github.com/llvm/llvm-project/pull/128420 to move predication to be VPlan-based and remove `HCFGBuilder.getIRBBForVPB`, which is only to enable the transition and should not have any new users added.

 There's one remaining issue related to early exits, for which we will have make some adjustments to how we generate single entry/exit regions, started in https://github.com/llvm/llvm-project/pull/128419 and some more follow-ups to initial preserve exiting edges.

https://github.com/llvm/llvm-project/pull/128187