mpn_mul_1
cy_limb = mpn_mul_1 (prodp, up, usize, v_limb);
cy_limb = mpn_mul_1 (prodp, up, size, v_limb);
cy_limb = mpn_mul_1 (prodp, up, size, v_limb);
cy_limb = mpn_mul_1 (prodp, up, usize, v_limb);
mp_limb_t mpn_mul_1 _PROTO ((mp_ptr, mp_srcptr, mp_size_t, mp_limb_t));