Not an LLVM issue, just hung with a downgraded LLVM 3.4. So the problem has to
be in mesa. I will now try to find the latest working version of mesa. Starting
from 10.1.4 for now.

Regarding recent two hangs. One was total, and I had to hard reset. The other,
that happened 10 minutes after reboot, wasn't that bad. After `pkill -9 kdm`
from SSH I was able to CTRL+ALT+F1. The error was "EQ overflow" again of
course, but has got a different stacktrace just a little bit.

However, X wasn't able to start again. I had to reboot.

[   480.971] (EE) RADEON(0): [drm] Failed to open DRM device for
pci:0000:01:00.0: No such file or directory