[llvm] [LoopInterchange] Enable it by default (WIP) (PR #124911)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

I would like to change the status from WIP to ready-to-merge as I believe the outstanding issues has been resolved:

The last two DependenceAnalysis bugs and patches that address them have been merged:
- https://github.com/llvm/llvm-project/pull/123436
- https://github.com/llvm/llvm-project/pull/116632

We have enabled interchange in the Flang driver and compiler:
- https://github.com/llvm/llvm-project/pull/140182

This has been running for a while now, and one bug was found and fixed (thanks @kasuga-fj ): 
- https://github.com/llvm/llvm-project/pull/140709

And another interchange bug was fixed:
- https://github.com/llvm/llvm-project/issues/140238

With all of this fixed, I think loop interchange is now ready to be turned on here too.

Shall we merge this, @Meinersbur , @kasuga-fj , @sebpop, @nikic, @mshockwave?


https://github.com/llvm/llvm-project/pull/124911