Created attachment 124845 [details]
output of the dmesg command

Symptoms:
Login screen renders properly
Past login, the screen turns black, with the pointer visible and a blank pixel
in the upper left corner.
On some occasion the pointer turns from the arrow to the vertical bar.
crtl+alt+F<whaterver> works and brings the user to the tty.

all symptoms are reverted when the llvm driver is used.

System:
Ubuntu 16.04 Gnome edition (but even with unity installed and configured as
default the symptoms are the same)
AMD Radeon RX 480 8G
AMDgpu-pro 16.30
4.4 kernel

The dmesg file is the output of the command after a tty return with
ctrl+alt+F4.

original description here:
https://www.phoronix.com/forums/forum/linux-graphics-x-org-drivers/amd-linux/881991-rx-480-on-ubuntu-has-anyone-been-able-to-use-it