[clang] [Clang][CodeGen] Start migrating away from assuming the Default AS is 0 (PR #88182)

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

> querying a modules global AS from the target, rather than from the data layout (some DL's are incomplete, e.g. SPIRV's)

That is a bug in those DataLayouts

https://github.com/llvm/llvm-project/pull/88182