[llvm] [InstCombineCompares] Try to "strengthen" compares based on known bits. (PR #79405)

[Mikhail Gudim via llvm-commits]

mgudim wrote:

@dtcxzyw I think it's better to limit this only to the case when result of `icmp` is used in branches. I pushed the commit with this change and I'll fix the tests soon.

https://github.com/llvm/llvm-project/pull/79405