The abilities of this hardware is too limited to support generic sign /
swizzle fixups. A generic handler would consume 4 of the 8 available
color instruction slots and 2 alpha instruction slots.

The bump mapping handler code has its own way of handling the color
fixups. It merges the fixup into the perturbation calculation without
requiring extra shader instructions. In theory this is possible for the
majority of d3d texture ops as well, but I don't think this is worth the
effort. I expect that this code will only be used for the ddraw signed
format test in practice.