Hmm... I'm not sure this is the best approach. You have a compare, and then a jump to deoptimize in the fastest case. A single jo to deoptimize would be tighter. The code for Math.abs is:

    public static int abs(int a) {
        return (a < 0) ? -a : a;
    }

Perhaps we'd be better off writing that inline, and then just replacing the - with ExactMath.subtractExact?

And then of course you'd need the fallback cases similar to as you have.

@chrisseaton updated to use ExactMath

Thanks - take a look at jt --asm of the two to see why it's better this way.