https://bugs.freedesktop.org/show_bug.cgi?id=65192
--- Comment #2 from Michel Dänzer michel@daenzer.net --- (In reply to comment #2)
Setting R600_HYPERZ=0 in /etc/environment didn't help.
Are you sure this ended up in the environment of the screensaver hacks? Can you try e.g.
R600_HYPERZ=0 /usr/lib/xscreensaver/antmaze
manually to see if that works better? Same thing might be interesting for R600_DEBUG=sb (or R600_LLVM=0, but AFAICT you're building without the r600g LLVM compiler backend anyway?).