Originally Posted by britelite
It has a modulo, which can be used as x increment, and which is perfect for this kind of gouraud shading (and other effects too).
It's a y modulo though. Better if it had X and Y for each source. Would have been nice to have an indirect addressing mode too. With halftone/smudge combined with destination f/l/m mask you can hflip or do brush magnification in 4 passes.
You can even do bitmap to b/w 16 bpp colour expansion