The last good known version is d571f2, and the first known bad version is
9f2050. 

I will try to narrow that a bit but, aAs stated, it is a bit difficult for me
to bisect. I am using oibaf's ppa which I can recompile myself in a chroot
environment. However, since I am not used to working with git I presume it will
be a bit tricky for me to obtain the diffs to be applied.

I know this is noob, but is there a way to obtain a diff between version from
http://cgit.freedesktop.org/mesa/mesa without having to clone the git repo?
That would surely help me identify the offending commit...