[llvm] [InstCombine] Add transforms for `icmp uPred (trunc x),(truncOrZext(y))` -> `icmp uPred x,y` (PR #71309)

[Nikita Popov via llvm-commits]

nikic wrote:

Should this be guarded by a shouldChangeType() heuristic? Say you're doing `icmp eq (trunc i256 to i32, trunc i256 to i32)`. Is folding that to `icmp eq i256` a good idea?

https://github.com/llvm/llvm-project/pull/71309