I can confirm lastest git head (50b49d242d702e4728329cc59f87d929963e7c53) still
causes lockups, though they seem to come much faster.

Also seems to have a regression regarding lighting, I'll see about bisecting
that in a separate report.

LLVM: 3.8.0
DRM: 2.43.0
Linux: 4.6.3-gentoo