bn_mulw_addw_addw
bn_mulw_addw_addw(a0, b, c0, d, &d, &r0);
bn_mulw_addw_addw(a1, b, c1, d, &d, &r1);
bn_mulw_addw_addw(a2, b, c2, d, &d, &r2);
bn_mulw_addw_addw(a3, b, c3, d, &d, &r3);
bn_mulw_addw_addw(ap[0], b, tp[0], *carry_a, carry_a, &x0);
bn_mulw_addw_addw(np[0], w, x0, *carry_n, carry_n, &tp[0]);
bn_mulw_addw_addw(a[0], w, r[0], carry, &carry, &r[0]);
bn_mulw_addw_addw(a[0], a[0], r[0], carry, &carry, &r[0]);