Comment # 21 on bug 64600 from Peter Wu

Works now with the latest mesa and llvm. If the performance is still bad, you
are probably affected by a bad workgroup size. In that case, try Tom's
pyrit-perfs[1][2] patches on top of ac81b6f2be8779022e8641984b09118b57263128.

The second patch[2] is already upstreamed, but patch [1] does not apply on the
current master because of other changes in the area.

 [1]:
http://people.freedesktop.org/~tstellar/pyrit-perf/0001-XXX-clover-Calculate-the-optimal-work-group-size.patch
 [2]:
http://people.freedesktop.org/~tstellar/pyrit-perf/0001-radeon-llvm-Specify-the-DataLayout-when-running-opti.patch