Figure out a strategy for source/dest modifiers
I've never really liked depending on NIR's modifiers in the back-end because NIR doesn't have any good concept of what modifiers are valid. We need to analyze different options and come up with a strategy that better fits our HW. That may be just to improve NIR modifiers and maybe we want to shut off NIR modifiers and do our own thing. Currently, we're doing the later but we're not doing it well.