The line "no SPIR support" indicates that the driver doesn't support SPIR. It is not an error, just an indication of the fact, since AMD dropped SPIR support at some point.
As for the number of compute units, we are using OpenCL call CL_DEVICE_MAX_COMPUTE_UNITS to get this number. It may be a specific of RDNA architecture that only half of the actual compute units number is returned. However, it shouldn't affect the device performance.