[llvm] [HashRecognize] Rewrite arePHIsIntertwined (PR #144878)

[Piotr Fusik via llvm-commits]

pfusik wrote:

Please also change `L`->`P1`, `R`->`P2` in the IR comment for clarity.

> > Now I think the XOR might be e.g. multiplied by a (runtime) zero
>
> I've added a test showing that the KnownBits propagation works.

KnownBits propagation is sufficient, do we even need to look for a XOR ?

> > or be one of the branches of a `SelectInst` that is never taken.
> 
> The XOR is checked in the condition of the select, not the branches.

I meant another `SelectInst` in the use-def chain of the condition.


https://github.com/llvm/llvm-project/pull/144878