Forgot to add:

direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: X.Org (0x1002)
    Device: AMD Radeon HD 7900 Series (TAHITI, DRM 3.27.0,
4.18.0-rc1-amd-staging-drm-next-git, LLVM 7.0.0) (0x6798)
    Version: 18.2.0
    Accelerated: yes
    Video memory: 3072MB
    Unified memory: no
    Preferred profile: core (0x1)
    Max core profile version: 4.5
    Max compat profile version: 4.4
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.1
OpenGL vendor string: X.Org
OpenGL renderer string: AMD Radeon HD 7900 Series (TAHITI, DRM 3.27.0,
4.18.0-rc1-amd-staging-drm-next-git, LLVM 7.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.2.0-devel
(git-6853862a58)
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 4.4 (Compatibility Profile) Mesa 18.2.0-devel
(git-6853862a58)
OpenGL shading language version string: 4.40
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile

OpenGL ES profile version string: OpenGL ES 3.1 Mesa 18.2.0-devel
(git-6853862a58)
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.10

I use latest linuxfirmware git to be able to use my Tahiti card with AMDGPU.