https://bugs.freedesktop.org/show_bug.cgi?id=98351
--- Comment #4 from Clemens Eisserer linuxhippy@gmail.com --- Worked out of the box - maybe radeonsi supports some extensions LO requires and r600 is missing?
After all, at least with mesa LO's OpenGL backend is not worth the trouble - it is slow and rendering isn't pixel-perfect.