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

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

Re: compile-times

I feel we are approaching bikeshed territory. I.e., with the geomean compile times that I shared earlier, there should be no reason for concerns, I think. If we are going to discuss what they should be, it is going to completely arbitrary. 
The concession I am willing to make is to enable this only with -O3.



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