[llvm] [InstCombine] Generalize `icmp (shl nuw C2, Y), C -> icmp Y, C3` (PR #104696)

[Nikita Popov via llvm-commits]

nikic wrote:

> Alive2: https://alive2.llvm.org/ce/z/0xcdE6

These proofs don't match the implementation. Note that the pow2 check is not a pre-condition of the transform, it is only used to adjust the predicate in some cases. There is no adjustment for ule predicates, so in that case I'd expect this to verify for the implementation to be correct: https://alive2.llvm.org/ce/z/wk4LYe

https://github.com/llvm/llvm-project/pull/104696