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