[llvm] [LoopPeel] Implement initial peeling off the last loop iteration. (PR #139551)

[Florian Hahn via llvm-commits]

fhahn wrote:

> This looks like a very useful improvement, thank you for working on this.

The initial version is still quite restricted, but I am planning on making various improvements in follow-ups, including the ones you mentiond (thanks!) and removing the minimum iteration restriction via a runtime check and better adjusting of the exit condition.

https://github.com/llvm/llvm-project/pull/139551