C can't do provenance

As I explained, the compiler is required to allow the programmer to reconstitute an arbitrary valid pointer from non-pointer data in multiple ways. So the optimization you describe is only possible if the compiler can either prove that you have not done that in a particular case, or if it can somehow prove that the pointers must not alias despite the fact that they may not obey strict provenance rules. In other words, this optimization only works in "easy" cases, and does not cover all legal uses of pointers. The compiler is required to disable it if it is not provably correct in a given case.

Provenance is not a matter of optimization. It is not "optional," and you cannot simply turn it off when it becomes inconvenient. It is a real feature of some hardware (e.g. CHERI) that makes it impossible to dereference a possibly-invalid pointer. On that hardware, manufacturing (and dereferencing) an arbitrary pointer out of non-pointer data traps. Walking off the end of an array traps. UAF and double free both trap. And there are probably several other things that trap, but I think you get the idea. All of these traps happen even if the pointer is numerically equal to a valid pointer that exists elsewhere in the program, and could be validly dereferenced at the same exact address. This is because, on that hardware, every pointer has associated metadata that tells the hardware whether it is valid, and over what range of addresses, so the hardware can check every dereference for validity (similar to Valgrind's memcheck tool, but much stricter because it is not required to be compatible with C). In the context of programming languages, "pointer provenance" generally means the set of restrictions that must be enforced in order for the language to be compatible with CHERI and similar architectures. I have not seen the term used to refer generically to knowing where some specific pointer came from - that's usually called escape analysis or pointer analysis.