[llvm] [InstCombine] Fold `switch(rol(x, C1)) case C2:` to `switch(x) case rol(C2, -C1):` (PR #86307)

[Nikita Popov via llvm-commits]

nikic wrote:

I don't really like the idea of SimplifyCFG and InstCombine changing the code back and forth. Maybe we should limit the fold to the case where it will not make the switch less dense?

https://github.com/llvm/llvm-project/pull/86307