(In reply to comment #12)
> Created attachment 69334 [details]
> Possible fix
> 
> This is a strange bug.  There must be a race condition somewhere.  Does this
> patch help?  If it doesn't, can you reproduce this with an LLVM 3.2 tree:
> 
> git fetch git://people.freedesktop.org/~tstellar/llvm master

I should add you need to build the branch of LLVM with
--enable-experimental-targets=AMDGPU