[llvm] [LoopInterchange] Add tests of 'S' deps (NFC) (PR #125214)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

The more testing the better, but I wanted to ask how these tests differ from existing S deps test? There are quite a few tests that we had to disable, and I have for example added some tests in https://github.com/llvm/llvm-project/pull/115900. I haven't looked closely how the new tests here differ, or what they add, so just wanted to ask you here. 

https://github.com/llvm/llvm-project/pull/125214