[clang] [llvm] [clang][amdgpu] Add builtins for raw/struct buffer lds load (PR #137678)

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

Side note, if we're cleaning up the API, we really should add s.buffer.load.real that actually models the memory effects correctly

https://github.com/llvm/llvm-project/pull/137678