Contrary to what's in the paper, I'm pretty sure IMUL-by-constant is in fact useful, since you can use subtraction: x * (a - b) === x * a - x * b and this a

Contrary to what's in the paper, I'm pretty sure IMUL-by-constant is in fact useful, since you can use subtraction: x * (a - b) === x * a - x * b and this applies even when losing the top half.