(In reply to Jarkko K from comment #3)
> 
> [Properties]
> "opengl.version"="3.0 Mesa 10.5.0-devel (git-d8da6de 2014-12-06
> trusty-oibaf-ppa)"

 That ppa still use llvm-3.5, OK. Yes i manage to reporuduce it now with
llvm-3.5 and with GFX Quality high setted in game, but with low issue is not
there.

 Anyway issue as i see is mostly fixed if current mesa is compiled against
llvm-3.6 svn. 

 I don't use ubuntu but you might want to try some ppas which does that like
this one - not day to day up to date, but hopefully should work at least for
you to check if this issue still appear there for you?

 https://launchpad.net/~paulo-miguel-dias/+archive/ubuntu/mesa