Comment # 2 on bug 57984 from Marek Olšák

(In reply to comment #1)
> I dug through the optimizations in r300_create_blend_state, and the problem
> is the "Disable reading if SRC_ALPHA == 0" optimization. It is not correct
> if the source factor is DEST_COLOR. I'm checking if any other source factors
> have to be excluded.

Yes, you're right. The optimization should check the source RGB and A factors
too.