You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: p256.go
    path of file: ./repos/gccrs/libgo/go/crypto/elliptic
    
    the code of the file until where you have to start completion: // Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//-go:build !amd64 && !arm64

package elliptic

// P-256 is implemented by various different backends, including a generic
// 32-bi
    
func p256PointAdd(xOut, yOut, zOut, x1, y1, z1, x2, y2, z2 *[p256Limbs]uint32) {
	var z1z1, z1z1z1, z2z2, z2z2z2, s1, s2, u1, u2, h, i, j, r, rr, v, tmp [p256Limbs]uint32

	p256Square(&z1z1, z1)
	p256Square(&z2z2, z2)
	p256Mul(&u1, x1, &z2z2)

	p256Sum(&tmp, z1, z2)
	p256Square(&tmp, &tmp)
	p256Diff(&tmp, &tmp, &z1z1)
	p256Diff(&tmp, &tmp, &z2z2)

	p256Mul(&z2z2z2, z2, &z2z2)
	p256Mul(&s1, y1, &z2z2z2)

	p256Mul(&u2, x2, &z1z1)
	p256Mul(&z1z1z1, z1, &z1z1)
	p256Mul(&s2, y2, &z1z1z1)
	p256Diff(&h, &u2, &u1)
	p256Sum(&i, &h, &h)
	p256Square(&i, &i)
	p256Mul(&j, &h, &i)
	p256Diff(&r, &s2, &s1)
	p256Sum(&r, &r, &r)
	p256Mul(&v, &u1, &i)

	p256Mul(zOut, &tmp, &h)
	p256Square(&rr, &r)
	p256Diff(xOut, &rr, &j)
	p256Diff(xOut, xOut, &v)
	p256Diff(xOut, xOut, &v)

	p256Diff(&tmp, &v, xOut)
	p256Mul(yOut, &tmp, &r)
	p256Mul(&tmp, &s1, &j)
	p256Diff(yOut, yOut, &tmp)
	p256Diff(yOut, yOut, &tmp)
}