[llvm] Reapply "[LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (#149042)" (PR #168738)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for putting this up.


> Can you add an mllvm option to opt out of this change? It causes AVX512 performance degradation.

I am currently looking at the AVX512 regression and was planning on resubmitting once we understood the root cause better.



https://github.com/llvm/llvm-project/pull/168738