BN_mod_sub_quick
if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field))
if (!BN_mod_sub_quick(rh, rh, tmp, p))
if (!BN_mod_sub_quick(n5, n1, n3, p))
if (!BN_mod_sub_quick(n6, n2, n4, p))
if (!BN_mod_sub_quick(&r->X, n0, n3, p))
if (!BN_mod_sub_quick(n0, n3, n0, p))
if (!BN_mod_sub_quick(n0, n0, n1, p))
if (!BN_mod_sub_quick(n2, &a->X, n1, p))
if (!BN_mod_sub_quick(&r->X, &r->X, n0, p))
if (!BN_mod_sub_quick(n0, n2, &r->X, p))
if (!BN_mod_sub_quick(&r->Y, n0, n3, p))
int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m);