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

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Yep, you're right, here are the right numbers:
> 
> http://llvm-compile-time-tracker.com/compare.php?from=bf60aa1c551ef5de62fd1d1cdcbff58cba55cacd&to=54b48e5d738fa763fb1f31590801b701262ce045&stat=instructions:u

I think this is quite a serious regression, especially given that there are no binary changes. Is the regression coming mostly from DA? In that case, can we try to early-exit in LoopInterchange and avoid computing DA, if there are likely going to be no binary changes?

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