[TBAA] Refine pointer-tbaa for void pointers by pointer depth (#126047)

Commit 77d3f8a avoids distinct tags for any pointers where the ultimate
pointee type is `void`, to solve breakage in real-world code that uses
(indirections to) `void*` for polymorphism over different pointer types.

While this matches the TBAA implementation in GCC, this patch implements
a refinement that distinguishes void pointers by pointer depth, as
described in the "strict aliasing" documentation included in the
aforementioned commit:
> `void*` is permitted to alias any pointer type, `void**` is permitted
> to alias any pointer to pointer type, and so on.

For example, `void**` is no longer considered to alias `int*` in this
refinement, but it remains possible to use `void**` for polymorphism
over pointers to pointers.

0 files changed, 0 insertions, 0 deletions