[llvm] [DataLayout] Add isNullPointerAllZeroes (PR #165314)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

I'm not sure what you are trying to do here. The null pointer (as in `ptr null`) is always all-zeroes, no matter the address space. What differs by address space is whether the all-zeroes pointer is assumed to be non-dereferenceable by default.

https://github.com/llvm/llvm-project/pull/165314