llvm/libclc/generic/include/clc/cl_khr_global_int32_base_atomics/atom_cmpxchg.h

_CLC_OVERLOAD _CLC_DECL int atom_cmpxchg(volatile global int *p, int cmp, int val);
_CLC_OVERLOAD _CLC_DECL unsigned int atom_cmpxchg(volatile global unsigned int *p, unsigned int cmp, unsigned int val);