In the very near future AMD will be releasing an updated driver, focused on improving performance in Prey and DiRT 4.
For DiRT 4 it will enable a Multi GPU profile and up to 30% performance improvement when using 8xMSAA on a Radeon RX 580 8GB compared to the previous release.
Prey is not quite so impressive, but you can expect a 4% boost on the same card. Drop by the driver page to grab them, or keep an eye out in your Catalyst Control Panel.
They need to stop doing
They need to stop doing performance fixes and focus on just fixing all the damn bugs they introduced and reintroduced with the RADEON SETTINGS rewrite.