From 63834fe8c11195ebf69db90d57f416c030f65230 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Tue, 15 Oct 2019 12:25:15 +0300
Subject: [PATCH] Remove non-AVX parts from avx package

Remove Inv(), Mul1(), And() because right now
they have no AVX optimizations.
---
 gf127/avx/gf127.go      | 70 -----------------------------------------
 gf127/avx/gf127_test.go | 24 --------------
 tz/sl2.go               | 10 +++---
 tz/sl2_test.go          |  2 +-
 4 files changed, 6 insertions(+), 100 deletions(-)

diff --git a/gf127/avx/gf127.go b/gf127/avx/gf127.go
index fe5bcbb..4072981 100644
--- a/gf127/avx/gf127.go
+++ b/gf127/avx/gf127.go
@@ -8,8 +8,6 @@
 package avx
 
 import (
-	"math/bits"
-
 	"github.com/nspcc-dev/tzhash/gf127"
 )
 
@@ -21,76 +19,8 @@ const msb64 = uint64(1) << 63
 var (
 	// x127x63 represents x^127 + x^63. Used in assembly file.
 	x127x63 = GF127{msb64, msb64}
-
-	// x126x631 is reduction polynomial x^127+x^63+1
-	x127x631 = GF127{msb64 + 1, msb64}
 )
 
-// Inv sets b to a^-1
-// Algorithm is based on Extended Euclidean Algorithm
-// and is described by Hankerson, Hernandez, Menezes in
-// https://link.springer.com/content/pdf/10.1007/3-540-44499-8_1.pdf
-func Inv(a, b *GF127) {
-	var (
-		v    = x127x631
-		u    = *a
-		c, d = &GF127{1, 0}, &GF127{0, 0}
-		t    = new(GF127)
-		x    *GF127
-	)
-
-	// degree of polynomial is a position of most significant bit
-	for du, dv := msb(&u), msb(&v); du != 0; du, dv = msb(&u), msb(&v) {
-		if du < dv {
-			v, u = u, v
-			dv, du = du, dv
-			d, c = c, d
-		}
-
-		x = xN(du - dv)
-
-		Mul(x, &v, t)
-		Add(&u, t, &u)
-
-		// becasuse mul performs reduction on t, we need
-		// manually reduce u at first step
-		if msb(&u) == 127 {
-			Add(&u, &x127x631, &u)
-		}
-
-		Mul(x, d, t)
-		Add(c, t, c)
-	}
-	*b = *c
-}
-
-func xN(n int) *GF127 {
-	if n < 64 {
-		return &GF127{1 << uint(n), 0}
-	}
-	return &GF127{0, 1 << uint(n-64)}
-}
-
-func msb(a *GF127) (x int) {
-	x = bits.LeadingZeros64(a[1])
-	if x == 64 {
-		x = bits.LeadingZeros64(a[0]) + 64
-	}
-	return 127 - x
-}
-
-// Mul1 copies a to b.
-func Mul1(a, b *GF127) {
-	b[0] = a[0]
-	b[1] = a[1]
-}
-
-// And sets c to a & b (bitwise-and).
-func And(a, b, c *GF127) {
-	c[0] = a[0] & b[0]
-	c[1] = a[1] & b[1]
-}
-
 // Add sets c to a+b.
 func Add(a, b, c *GF127)
 
diff --git a/gf127/avx/gf127_test.go b/gf127/avx/gf127_test.go
index b7f1ba9..9da629c 100644
--- a/gf127/avx/gf127_test.go
+++ b/gf127/avx/gf127_test.go
@@ -66,27 +66,3 @@ func TestMul11(t *testing.T) {
 		require.Equal(t, tc[1], c)
 	}
 }
-
-var testCasesInv = [][2]*GF127{
-	{&GF127{1, 0}, &GF127{1, 0}},
-	{&GF127{3, 0}, &GF127{msb64, ^msb64}},
-	{&GF127{54321, 12345}, &GF127{8230555108620784737, 3929873967650665114}},
-}
-
-func TestInv(t *testing.T) {
-	var a, b, c = new(GF127), new(GF127), new(GF127)
-	for _, tc := range testCasesInv {
-		Inv(tc[0], c)
-		require.Equal(t, tc[1], c)
-	}
-
-	for i := 0; i < 3; i++ {
-		// 0 has no inverse
-		if a = gf127.Random(); a.Equals(&GF127{0, 0}) {
-			continue
-		}
-		Inv(a, b)
-		Mul(a, b, c)
-		require.Equal(t, &GF127{1, 0}, c)
-	}
-}
diff --git a/tz/sl2.go b/tz/sl2.go
index 11ff316..e0a4d8a 100644
--- a/tz/sl2.go
+++ b/tz/sl2.go
@@ -130,11 +130,11 @@ func (c *sl2) MulA() *sl2 {
 	var a GF127
 
 	avx.Mul10(&c[0][0], &a)
-	avx.Mul1(&c[0][0], &c[0][1])
+	gf127.Mul1(&c[0][0], &c[0][1])
 	avx.Add(&a, &c[0][1], &c[0][0])
 
 	avx.Mul10(&c[1][0], &a)
-	avx.Mul1(&c[1][0], &c[1][1])
+	gf127.Mul1(&c[1][0], &c[1][1])
 	avx.Add(&a, &c[1][1], &c[1][0])
 
 	return c
@@ -143,12 +143,12 @@ func (c *sl2) MulA() *sl2 {
 func (c *sl2) MulB() *sl2 {
 	var a GF127
 
-	avx.Mul1(&c[0][0], &a)
+	gf127.Mul1(&c[0][0], &a)
 	avx.Mul10(&c[0][0], &c[0][0])
 	avx.Add(&c[0][1], &c[0][0], &c[0][0])
 	avx.Add(&c[0][0], &a, &c[0][1])
 
-	avx.Mul1(&c[1][0], &a)
+	gf127.Mul1(&c[1][0], &a)
 	avx.Mul10(&c[1][0], &c[1][0])
 	avx.Add(&c[1][1], &c[1][0], &c[1][0])
 	avx.Add(&c[1][0], &a, &c[1][1])
@@ -172,7 +172,7 @@ func inv(a, b *sl2, t *[2]GF127) {
 	avx.Mul(&a[0][0], &a[1][1], &t[0])
 	avx.Mul(&a[0][1], &a[1][0], &t[1])
 	avx.Add(&t[0], &t[1], &t[0])
-	avx.Inv(&t[0], &t[1])
+	gf127.Inv(&t[0], &t[1])
 
 	avx.Mul(&t[1], &a[0][0], &b[1][1])
 	avx.Mul(&t[1], &a[0][1], &b[0][1])
diff --git a/tz/sl2_test.go b/tz/sl2_test.go
index e3a9190..d43fec8 100644
--- a/tz/sl2_test.go
+++ b/tz/sl2_test.go
@@ -26,7 +26,7 @@ func random() (a *sl2) {
 	avx.Add(&a[1][1], gf127.New(1, 0), &a[1][1])
 
 	t := gf127.New(0, 0)
-	avx.Inv(&a[0][0], t)
+	gf127.Inv(&a[0][0], t)
 	avx.Mul(t, &a[1][1], &a[1][1])
 
 	return