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

[via llvm-commits]

XChy wrote:

I think folding it if the number of reachable successors <= 3 is OK, because the backend doesn't create a lookup table in this case, and the real-world case in original issue also holds only 3 successors.

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