[libclc] [libclc] Add generic implementation of some atomic functions in OpenCL spec section 6.15.12.7 (PR #146814)

[Fraser Cormack via cfe-commits]

https://github.com/frasercrmck commented:

Can we do anything about the warnings I'm seeing while building this? They're noisy.


```
In file included from /llvm-project/libclc/clc/lib/generic/atomic/clc_atomic_fetch_min.cl:18:
In file included from /llvm-project/libclc/clc/include/clc/math/gentype.inc:239:
/llvm-project/libclc/clc/lib/generic/atomic/atomic_def.inc:59:1: warning: large atomic operation may incur significant performance penalty; the access size (2 bytes) exceeds the max lock-free size (0 bytes) [-Watomic-alignment]
   59 | __CLC_DEFINE_ATOMIC()
      | ^
/llvm-project/libclc/clc/lib/generic/atomic/atomic_def.inc:51:9: note: expanded from macro '__CLC_DEFINE_ATOMIC'
   51 |         __IMPL_FUNCTION((ADDRSPACE __CLC_PTR_CASTTYPE *)Ptr, Value,            \
      |         ^
/llvm-project/libclc/clc/lib/generic/atomic/clc_atomic_fetch_min.cl:12:25: note: expanded from macro '__IMPL_FUNCTION'
   12 | #define __IMPL_FUNCTION __scoped_atomic_fetch_min
      |                         ^

https://github.com/llvm/llvm-project/pull/146814