174 lines
3.2 KiB
Go
174 lines
3.2 KiB
Go
// +build !amd64,!arm64 generic
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package bn256
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func gfpCarry(a *gfP, head uint64) {
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b := &gfP{}
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var carry uint64
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for i, pi := range p2 {
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ai := a[i]
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bi := ai - pi - carry
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b[i] = bi
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carry = (pi&^ai | (pi|^ai)&bi) >> 63
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}
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carry = carry &^ head
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// If b is negative, then return a.
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// Else return b.
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carry = -carry
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ncarry := ^carry
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for i := 0; i < 4; i++ {
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a[i] = (a[i] & carry) | (b[i] & ncarry)
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}
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}
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func gfpNeg(c, a *gfP) {
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var carry uint64
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for i, pi := range p2 {
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ai := a[i]
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ci := pi - ai - carry
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c[i] = ci
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carry = (ai&^pi | (ai|^pi)&ci) >> 63
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}
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gfpCarry(c, 0)
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}
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func gfpAdd(c, a, b *gfP) {
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var carry uint64
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for i, ai := range a {
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bi := b[i]
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ci := ai + bi + carry
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c[i] = ci
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carry = (ai&bi | (ai|bi)&^ci) >> 63
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}
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gfpCarry(c, carry)
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}
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func gfpSub(c, a, b *gfP) {
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t := &gfP{}
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var carry uint64
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for i, pi := range p2 {
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bi := b[i]
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ti := pi - bi - carry
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t[i] = ti
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carry = (bi&^pi | (bi|^pi)&ti) >> 63
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}
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carry = 0
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for i, ai := range a {
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ti := t[i]
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ci := ai + ti + carry
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c[i] = ci
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carry = (ai&ti | (ai|ti)&^ci) >> 63
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}
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gfpCarry(c, carry)
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}
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func mul(a, b [4]uint64) [8]uint64 {
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const (
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mask16 uint64 = 0x0000ffff
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mask32 uint64 = 0xffffffff
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)
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var buff [32]uint64
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for i, ai := range a {
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a0, a1, a2, a3 := ai&mask16, (ai>>16)&mask16, (ai>>32)&mask16, ai>>48
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for j, bj := range b {
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b0, b2 := bj&mask32, bj>>32
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off := 4 * (i + j)
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buff[off+0] += a0 * b0
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buff[off+1] += a1 * b0
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buff[off+2] += a2*b0 + a0*b2
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buff[off+3] += a3*b0 + a1*b2
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buff[off+4] += a2 * b2
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buff[off+5] += a3 * b2
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}
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}
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for i := uint(1); i < 4; i++ {
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shift := 16 * i
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var head, carry uint64
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for j := uint(0); j < 8; j++ {
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block := 4 * j
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xi := buff[block]
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yi := (buff[block+i] << shift) + head
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zi := xi + yi + carry
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buff[block] = zi
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carry = (xi&yi | (xi|yi)&^zi) >> 63
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head = buff[block+i] >> (64 - shift)
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}
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}
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return [8]uint64{buff[0], buff[4], buff[8], buff[12], buff[16], buff[20], buff[24], buff[28]}
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}
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func halfMul(a, b [4]uint64) [4]uint64 {
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const (
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mask16 uint64 = 0x0000ffff
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mask32 uint64 = 0xffffffff
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)
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var buff [18]uint64
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for i, ai := range a {
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a0, a1, a2, a3 := ai&mask16, (ai>>16)&mask16, (ai>>32)&mask16, ai>>48
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for j, bj := range b {
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if i+j > 3 {
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break
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}
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b0, b2 := bj&mask32, bj>>32
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off := 4 * (i + j)
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buff[off+0] += a0 * b0
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buff[off+1] += a1 * b0
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buff[off+2] += a2*b0 + a0*b2
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buff[off+3] += a3*b0 + a1*b2
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buff[off+4] += a2 * b2
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buff[off+5] += a3 * b2
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}
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}
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for i := uint(1); i < 4; i++ {
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shift := 16 * i
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var head, carry uint64
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for j := uint(0); j < 4; j++ {
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block := 4 * j
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xi := buff[block]
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yi := (buff[block+i] << shift) + head
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zi := xi + yi + carry
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buff[block] = zi
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carry = (xi&yi | (xi|yi)&^zi) >> 63
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head = buff[block+i] >> (64 - shift)
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}
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}
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return [4]uint64{buff[0], buff[4], buff[8], buff[12]}
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}
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func gfpMul(c, a, b *gfP) {
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T := mul(*a, *b)
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m := halfMul([4]uint64{T[0], T[1], T[2], T[3]}, np)
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t := mul([4]uint64{m[0], m[1], m[2], m[3]}, p2)
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var carry uint64
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for i, Ti := range T {
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ti := t[i]
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zi := Ti + ti + carry
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T[i] = zi
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carry = (Ti&ti | (Ti|ti)&^zi) >> 63
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}
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*c = gfP{T[4], T[5], T[6], T[7]}
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gfpCarry(c, carry)
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}
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