One option is to try polishing the glass with a pad and polish specifically designed for auto glass. There are kits out there, however, the pits won't disappear. I have not seen a filler or resin that can fill the small chips in the glass. The only option that really works is replacing the windshield which is probably not the answer you want to hear.
Glass on the M3 and now all BMW's are really soft and chip easily. Highways beat the crap out of my windshield it's pretty sad.