[llvm] [Transforms][Utils] Add LoopSplitUtils for iteration-space loop splitting (PR #205995)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Please see inline for some code that looks like it might miscompile, crash or is not covered by existing tests.

It would have been good to try to break down the changes into smaller chunks, as the current size makes reviewing quite challenging.

It looks like there are a few pieces that could be added incrementally, like exit value support etc.

https://github.com/llvm/llvm-project/pull/205995