I'm running on a MacBook Pro 2016, with Radeon Pro 455 and the latest OS update.
Apart from the memory leaks and missing CL_SNORM_INT16 support previously mentioned, it looks like clEnqueueFillBuffer fails miserably to do what it's supposed to do. It seems to sometimes at least write something to the buffer, but not the pattern. Works okay using Intel graphics on the same Mac.
By the way, is there any point of reporting here? Should I report to Apple? Or do I just stick to Intel graphics and tell users that AMD on Macs is useless?