Comment # 46 on bug 80419 from darkm00n

Tested on Ubuntu 15.04 with Oibaf PPA, same thing happens...

mesa 10.6~git1504011930.5604d7~gd~v
xserver-xorg-video-ati 1:7.5.0-1ubuntu2
libllvm3.6 1:3.6-2ubuntu1
kernel 3.19.0.11.10

The saddest part is that game runs much smoother with mesa driver than with
fglrx.