Unless you are very familiar with the firearm and have handled it a great deal, I would probably do without a backup weapon. If you are close enough to shoot one with a bow, you probably aren't going to be quick enough with a firearm to do you any good. Fumbling around with a gun would make you a sitting duck IF a hog charged.

I hunt with a gun, so I don't carry a backup. But so far, I have not been charged by a hog I have shot. Most simply drop dead. A few times, I have had to shoot a hog twice. Usually, they are hiding in the brush, I shoot the part of them I can see, they run out, and I shoot them in the head. Even those hogs have not attacked. They usually try to run away before I can deliver a fatal shot. I've had a few run in my general direction, but they were not charging. They had no clue where the shot came from, and just picked a direction and hauled ham.

Same for hogs my dog is trailing. They will try to turn and fight him, but as soon as they see me, they turn and run. They will run until the dog closes again, turn to fight, then run again. Eventually, they tire and just try to stand the dog off. I shoot them and that's that.