GLV2 supports GT::pow

include/mcl/bn.hpp

@@ -859,7 +859,7 @@ struct GLV2 {
 	template<class T>
 	void mul(T& Q, const T& P, mpz_class x, bool constTime = false) const
 	{
-#if 0
+#if 1
 		const int w = 5;
 		const size_t tblSize = 1 << (w - 2);
 		const size_t splitN = 4;
@@ -877,14 +877,14 @@ struct GLV2 {
 			x += r;
 		}
 		split(u, x);
-		for (size_t i = 0; i < splitN; i++) {
-			gmp::getNAFwidth(&b, naf[i], u[i], w);
-			assert(b); (void)b;
-		}
 		tbl[0][0] = P;
 		Frobenius(tbl[1][0], tbl[0][0]);
 		Frobenius(tbl[2][0], tbl[1][0]);
 		Frobenius(tbl[3][0], tbl[2][0]);
+		for (size_t i = 0; i < splitN; i++) {
+			gmp::getNAFwidth(&b, naf[i], u[i], w);
+			assert(b); (void)b;
+		}
 		{
 			T P2;
 			T::dbl(P2, P);

include/mcl/fp_tower.hpp

@@ -1336,6 +1336,12 @@ struct GroupMtoA : public T {
 	{
 		T::mul(castT(z), castT(x), castT(y));
 	}
+	static void sub(GroupMtoA& z, const GroupMtoA& x, const GroupMtoA& y)
+	{
+		T r;
+		T::unitaryInv(r, castT(y));
+		T::mul(castT(z), castT(x), r);
+	}
 	static void dbl(GroupMtoA& y, const GroupMtoA& x)
 	{
 		T::sqr(castT(y), castT(x));
@@ -1363,6 +1369,10 @@ struct GroupMtoA : public T {
 	{
 		add(*this, *this, rhs);
 	}
+	void operator-=(const GroupMtoA& rhs)
+	{
+		sub(*this, *this, rhs);
+	}
 	void normalize() {}
 private:
 	bool isOne() const;