The RadeonSI driver for the very latest AMD graphics hardware is still a ways behind the "R600g" stack that spans supporting the Radeon HD 2000 through HD 6000 series hardware. (For that coverage, see AMD Radeon Gallium3D More Competitive With Catalyst On Linux.) Fortunately, the RadeonSI support is slowly but surely catching up.
Approaching a year and a half since the HD 7000 series debut, 2D tiling to boost performance is now supported by the xf86-video-ati X.Org driver and RadeonSI Gallium3D driver. The Gallium3D driver was also updated to support compressed textures. The notable Mesa commits are here and here. Te xf86-video-ati DDX commit is here.
Leveraging the tiling support requires using the new libdrm 2.4.44 release in conjunction with the rest of the updated user-space. This support has been in development for several weeks.
RadeonSI Gallium3D vs. Catalyst benchmarks are forthcoming on Phoronix.