return e
}

// Sub sets e = t1 - t2, and returns e.
func (e *P521Element) Sub(t1, t2 *P521Element) *P521Element {
	p521Sub(&e.x, &t1.x, &t2.x)
	return e
}

// Mul sets e = t1 * t2, and returns e.
func (e *P521Element) Mul(t1, t2 *P521Element) *P521Element {
	p521Mul(&e.x, &t1.x, &t2.x)
	return e
}

// Square sets e = t * t, and returns e.
func (e *P521Element) Square(t *P521Element) *P521Element {

	out1[7] = x46
	out1[8] = x47
}

// p521Sub subtracts two field elements in the Montgomery domain.
//
// Preconditions:
//
//	0 ≤ eval arg1 < m
//	0 ≤ eval arg2 < m
//
// Postconditions:
//
//	eval (from_montgomery out1) mod m = (eval (from_montgomery arg1) - eval (from_montgomery arg2)) mod m
//	0 ≤ eval out1 < m

	z3 := new(fiat.P521Element).Mul(p521B(), t2) // Z3 := b * t2
	x3.Sub(y3, z3)                               // X3 := Y3 - Z3
	z3.Add(x3, x3)                               // Z3 := X3 + X3
	x3.Add(x3, z3)                               // X3 := X3 + Z3
	z3.Sub(t1, x3)                               // Z3 := t1 - X3
	x3.Add(t1, x3)                               // X3 := t1 + X3
	y3.Mul(p521B(), y3)                          // Y3 := b * Y3