[llvm] [LoopInterchange] Don't consider loops with BTC=0 (PR #167113)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

> Can you please merge or rebase main instead of committing the same changes as #167748?

This is rebased/merged. The changes here to pr43326.ll and pr57148.ll should indeed have been included in #167748, but I missed them earlier. They were a bit masked by other things, and I discovered them during the rebase/changes here.

Thanks for the review and remarks, I am now addressing them. 



https://github.com/llvm/llvm-project/pull/167113