[clang] [llvm] [Clang][AMDGPU] Expose buffer load lds as a clang builtin (PR #132048)

[Juan Manuel Martinez Caamaño via llvm-commits]

jmmartinez wrote:

I've also seen that gfx11 seem to have some kind of BUFFER_LOAD_LDS_(SIZE) instruction (different from the BUFFER_LOAD_(SIZE)_LDS instructions associated with this builtin). 

However, I'm not sure they actually exists: we do not have any test where we generate them and the gfx11 shader manual explicitly says *"Remove "LOAD_LDS" instructions: buffer_load_lds, scratch_load_lds, global_load_lds"*

https://github.com/llvm/llvm-project/pull/132048