[llvm] [LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (WIP) (PR #149042)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

ping :)

this should be ready now, with first-order recurrences also handled

https://github.com/llvm/llvm-project/pull/149042