https://bugs.freedesktop.org/show_bug.cgi?id=80419
--- Comment #123 from Nicolai Hähnle nhaehnle@gmail.com --- Thanks for the re-test. It's odd that I couldn't reproduce it any more. It may be that I was just lucky.
However, it's worth noting that Daniel has a GCN 1.0 card and David has a GCN 1.1 card, i.e. running on the radeon kernel module and DDX. It's possible that an amdgpu-only change has randomly fixed this for my Tonga-based test setup.