I see the "GPU Workload" option in the AMD Settings application, but when I select "Compute" and accept the restart, it reverts back to "Graphics". I have more than one machine and have varying GPUs (470/480/570/580). On neither machine does the "Compute" option persist. I got it working once for one machine at the very beginning and saw a very noticeable difference in computation. After restarting that machine, the option would never persist. I was never able to get the "Compute" option to persist on the other machine.
This is unfortunate, because the preliminary results of the "Compute" workload looked extremely promising. I am using the 17.12.2 driver, but I am not sure if this worked better on older versions as I only started playing with it today.