Comment # 1 on bug 91828 from Michel Dänzer

(In reply to iive from comment #0)
> I know that R600 LLVM is not under active development. However at the moment
> that code is crashing on regular basis. Mesa should be able to work with any
> recent LLVM release and 3.6.2 is the latest current release. If you do not
> intend to maintain it, then you might consider removing it.

It's why it's disabled by default both at build time and at runtime. At this
point, it should only be enabled by someone who wants to work on fixing it.