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

[Jon Chesterfield via llvm-commits]

JonChesterfield wrote:

There's some existing builtin stuff going on in this area, e.g. https://github.com/llvm/llvm-project/pull/138141/commits/96e94b5662c613fd80f712080751076254a73524

The use case in CK is behind a hip header file, so could become static inline functions renaming a builtin, or could pick up some other dispatch.

I'm leaning slightly towards an automatic conversion between the two forms within LLVM not being worth the hassle. Inclined to abandon this PR, looks like it doesn't make sense within the wider context, but will leave it open for a while in case people comment further.

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