OpenGL renderer string: AMD RV710 (DRM 2.50.0 / 4.13.0-32-generic, LLVM 5.0.0)
OpenGL core profile version string: 3.3 (Core Profile) Mesa 18.1.0-devel (git-2d5b5d267e)
git bisect brought me to this commit:
I can't confirm this neither for AMD BARTS, nor for AMD CEDAR on
DRM 2.50.0 / 4.14.16-gentoo, LLVM 5.0.1 (0x68f9)
OpenGL core profile version string: 3.3 (Core Profile) Mesa 18.1.0-devel
So I guess this bug only affects pre Evergreen cards.
Should fix it, I tested on my rv770, sorry for breakage.
I can confirm that this patch fixed rendering for me. Thank you.