ramp::ll
pub unsafe fn mul(wp: LimbsMut, xp: Limbs, xs: i32, yp: Limbs, ys: i32)
Multiplies {xp, xs} by {yp, ys}, storing the result to {wp, xs + ys}.
{xp, xs}
{yp, ys}
{wp, xs + ys}
{wp, xs + ys} must be disjoint from both inputs.