The Open CL 1.2 barrier() function is threadgroup scope, same as threadgroup_barrier on Metal. OpenCL 2.0 introduced a proper barrier function (work_group_barri

The Open CL 1.2 barrier() function is threadgroup scope, same as threadgroup_barrier on Metal. OpenCL 2.0 introduced a proper barrier function (work_group_barrier), which takes a memory scope parameter, which can be memory_scope_device (all this is pretty similar to the Vulkan memory model, and at least some of the same people worked on both). I know of no way to reliably support those semantics on Metal. Claiming OpenCL bitcode is "forward compatible" is a pretty strong claim considering that OpenCL has been deprecated for over 3 years, and the main thing you get when searching OpenCL docs on the Apple site is an exhortation to migrate to Metal. To the extent there's a forward compatibility guarantee for AIR, I'm sure it only applies to output generated by official Apple tools, and I'm pretty sure by now there's no way to get those to output a device-scope barrier.