Implementation of atomic_ref::load with memory_scope_work_item

[VerenaBeckham]

Specification Version

SYCL 2020 (Revision 11)

Section Number(s)

4.15.3. Atomic references
(https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#sec:atomic-references)

Issue Description

atomic_ref::load() accepts all memory scopes. In OpenCL this would map to atomic_load_explicit() AIUI, but that API is not allowed with a work_item scope. See OpenCL spec (https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#memory-scope):

memory_scope_work_item can only be used with atomic_work_item_fence with flags set to CLK_IMAGE_MEM_FENCE.

This I take to mean memory_scope_work_item is only allowed to be used by the fence API.

Are we saying atomic_ref::load() with memory_scope::work_item needs to be implemented in some other way? Or should it be restricted to match OpenCL (#665 seems to say otherwise)? Or should this be added to OpenCL?

Code Example (Optional)

No response

[TApplencourt]

Todo: Get point of view of OpenCL people.