Phoronix published a review on the 2016 End-of-Year Open-Source Radeon Benchmarks With Linux 4.9, Mesa 13.1-dev On Many Different GPUs A quote from the article:

With 2016 soon drawing to an end, it's time for all of my year-end recaps now of Linux drivers that I have been doing for the past 12 years. Today are benchmarks of a wide assortment of AMD graphics cards on both R600g and RadeonSI Gallium3D drivers when using Mesa 13.1-dev + LLVM 4.0 SVN and the Linux 4.9 kernel for providing a bleeding-edge look at the open-source AMD Linux graphics performance across hardware going from the Radeon HD 4890 series all the way up through the RX 480 and R9 Fury hardware. Here's a fun look at the OpenGL driver performance across this range of GPUs.

 2016 End-of-Year Open-Source Radeon Benchmarks With Linux 4.9, Mesa 13.1-dev On Many Different GPUs @ Phoronix