See image. Not seeing a GPU workload option to switch to compute mode. Running an RX 580 black core edition, driver version 17.12.1, win 7 professional edition. Did a clean install with the updater and again with the amd clean uninstall utility, still don't see the setting.
The same here with Sapphire Nitro+ RX580 8GB Special Edition using 17.12.2, also together with Windows 7 64 Bit Professional.
Don't have to upload a picture because it would look the same as yours :-D