(In reply to comment #3)
> (In reply to comment #2)
> > I can't reproduce this with LLVM r179895 and Mesa
> > 12eab7cc564a6928197f9b87ded9e368e56976f0
> > 
> > Have you done full rebuilds of both projects?
> 
> Yes, I always do make [dist]clean and git clean -dfx.
> 
> I have just deleted both trees and re-cloned to be sure, but the segfault is
> still there.
> 
> When I was on my working commits moving either llvm or mesa to head while
> keeping the other on "working" produced the segfault (which is why I didn't
> do a proper bisect).
> 
> I always clean and rebuild mesa after llvm has changed.

I was able to reproduce this on my gentoo system, but not on either of my
fedora systems.  I will investigate further, what distro are you using?