[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Slava Zakharin via llvm-commits]

vzakhari wrote:

Performance has restored back. Thank you!  I also see a significant performance improvement on zen4 - just wondering if this is expected (I did not verify which commit caused this, but it is in the same timeframe as the follow-up fix here).

https://github.com/llvm/llvm-project/pull/132190