[clang] [clang-tools-extra] [Clang] Use TargetInfo when deciding is an address space is compatible (PR #115777)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> I updated the patch to use target info instead, this doesn't affect OpenCL because they don't use the `DefaultAS`. I would appreciate some information from the people who know the standards better than I.

As best I can tell, this seems correct to me, at least from the perspective of the TR (it's possible that our uses of address spaces have diverged from the TR though, I'm not an expert in address spaces by any means!). One thing I think we need to do is actually document the address space relationships so users know which ones are disjoint, which are equivalent, and which are subsets (and this may be target-specific documentation).

I'd love to hear from other folks who may have had prior exposure to address spaces: @AnastasiaStulova @rjmccall @efriedma-quic @jyknight (others?)

https://github.com/llvm/llvm-project/pull/115777