mpn_sub_n
mpn_sub_n (np, np, dp, dsize);
mpn_sub_n (prodp, up + hsize, up, hsize);
mpn_sub_n (prodp, up, up + hsize, hsize);
mpn_sub_n (prodp + hsize, vp + hsize, vp, hsize);
mpn_sub_n (prodp + hsize, vp, vp + hsize, hsize);
cy -= mpn_sub_n (prodp + hsize, prodp + hsize, tspace, size);
mpn_sub_n (prodp, up + hsize, up, hsize);
mpn_sub_n (prodp, up, up + hsize, hsize);
cy -= mpn_sub_n (prodp + hsize, prodp + hsize, tspace, size);
mpn_sub_n (res_ptr, s1_ptr, s2_ptr, size)
mp_limb_t mpn_sub_n _PROTO ((mp_ptr, mp_srcptr, mp_srcptr, mp_size_t));
cy_limb = mpn_sub_n (res_ptr, s1_ptr, s2_ptr, s2_size);