https://bugs.freedesktop.org/show_bug.cgi?id=54767
--- Comment #5 from Marek Olšák maraeo@gmail.com --- (In reply to comment #4)
Does that include atan(vec4, vec4) in fragment shader? I have a Radeon 9800 Pro 128MB (R350).
I don't remember if that function works on r300. I guess you have to try and see if the results are correct but not very precise (i.e. they're close to the expected value) or if they're totally wrong.