[llvm] [LoopInterchange] Constrain LI within supported loop nest depth (PR #118656)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur approved this pull request.

> Sure, let me rerun again with compile-time-tracker.

If you want to check the influence of the max-depth bound with enabled loop-interchange, you would need it based on the commit that has if enabled.

I don't think any of the sources from test-suite used by by the compile-time-tracker has loops that deep. I don't think it matters anyway, based on bubble-sort already is a convinving argument that an upper bound it needed.

Not relying on `-debug` would be nice, but still common practice that I don't want to suddenly enforce.

LGTM. Be sure to remove `cl::init(true)` before pushing[^1].

[^1]: Could have used a different branch for experimentation, `bound-max-depth-2` is identical, `enable-li-2` is based on a different commit and doesn't show up as direct comparison in llvm-compile-tracker.

https://github.com/llvm/llvm-project/pull/118656