https://bugs.freedesktop.org/show_bug.cgi?id=32296
--- Comment #7 from Marek Olšák maraeo@gmail.com 2011-01-25 07:53:05 PST --- The zigzagged edges (those little deterministic squares of corruption) are a HiZ issue. Currently I am only fixing Zmask (zbuffer compression).
I've made a new patch, which contains new bug fixes and performance should no longer regress. Could you give it a try?
https://bugs.freedesktop.org/attachment.cgi?id=42464