https://bugs.freedesktop.org/show_bug.cgi?id=79575
--- Comment #6 from Michel Dänzer michel@daenzer.net --- (In reply to comment #5)
I tried adding R600_DEBUG=fs but no extra info was printed.
That should be R600_DEBUG=ps for the pixel/fragment shader (you can see a list of supported debugging options with R600_DEBUG=help).
Anyway, this is probably related to comment #3.