[llvm] [ValueTracking] Respect `samesign` flag in `isKnownInversion` (PR #112390)

[Antonio Frighetto via llvm-commits]

https://github.com/antoniofrighetto commented:

> * Alternative solution 3: Drop all poison-generating flags in InstCombine if `FalseVal` is an ICmp/Instruction
>   
>   * Pros: simple/fast
>   * Cons: instruction-dependent/hard to extend

Out of curiosity, how come is it a cons if it happens to be instruction-dependant? It doesn't seem to be necessarily so to me? Current solution looks fine to me.

https://github.com/llvm/llvm-project/pull/112390