[llvm] [WIP] Consider datalayout sentinel pointer value for isKnownNonZero check (PR #91769)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic requested changes to this pull request.

> Pointers can have contain an all-zero value no matter what the sentinel value is.

https://github.com/llvm/llvm-project/pull/91769