Created attachment 130218 [details]
default UE4 fragment shader
UE4Editor (with -opengl3) seems to run reasonably well on r600/ARUBA using Mesa version 13.0, apart from the failure to compile the attached default fragment shader.
This shader uses many arrays, and hence, reserves more registers that the r600 hardware supports.
A work-in-progress patch series that fixes this can be found at
The according series has been pushed.
With the work landed, I think we can close this. Gert, feel free to open if I've missed something.