Comment # 5 on bug 54767 from Marek Olšák

(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.