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Avoid conversions to/from [u64; 4] in BigInteger256 methods
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@sebastiencs
sebastiencs committed Dec 4, 2024
1 parent f42a8ec commit d0343f5
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Showing 2 changed files with 47 additions and 53 deletions.
98 changes: 46 additions & 52 deletions ff/src/biginteger/webnode.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ use num_bigint::BigUint;
use zeroize::Zeroize;

use crate::{FromBytes, ToBytes};
use crate::fields::webnode::MASK;

use super::BigInteger;

Expand Down Expand Up @@ -52,125 +53,121 @@ impl BigInteger for BigInteger256 {
#[inline]
#[ark_ff_asm::unroll_for_loops]
fn add_nocarry(&mut self, other: &Self) -> bool {
let mut this = self.to_64x4();
let other = other.to_64x4();

let mut carry = 0;
for i in 0..4 {
this[i] = adc!(this[i], other[i], &mut carry);
for i in 0..9 {
self.0[i] = {
let tmp = self.0[i] as u64 + other.0[i] as u64 + carry;
carry = tmp >> 29;
(tmp as u32) & MASK
};
}
*self = Self::from_64x4(this);
carry != 0
}

#[inline]
#[ark_ff_asm::unroll_for_loops]
fn sub_noborrow(&mut self, other: &Self) -> bool {
let mut this = self.to_64x4();
let other = other.to_64x4();

let mut borrow = 0;
for i in 0..4 {
this[i] = sbb!(this[i], other[i], &mut borrow);
for i in 0..9 {
self.0[i] = {
let tmp = (1u64 << 29) + (self.0[i] as u64) - (other.0[i] as u64) - (borrow as u64);
borrow = if tmp >> 29 == 0 {
1
} else {
0
};
(tmp as u32) & MASK
};
}
*self = Self::from_64x4(this);
borrow != 0
}

#[inline]
#[ark_ff_asm::unroll_for_loops]
#[allow(unused)]
fn mul2(&mut self) {
let mut value = self.to_64x4();
let mut last = 0;
for i in 0..4 {
let a = &mut value[i];
let tmp = *a >> 63;
*a <<= 1;
*a |= last;
for i in 0..9 {
let a = &mut self.0[i];
let tmp = (*a as u64) >> 28;
*a = (*a << 1) & MASK;
*a |= last as u32;
last = tmp;
}
*self = Self::from_64x4(value)
}

#[inline]
#[ark_ff_asm::unroll_for_loops]
fn muln(&mut self, mut n: u32) {
let mut value = self.to_64x4();
if n >= 64 * 4 {
*self = Self::from(0);
return;
}

while n >= 64 {
while n >= 29 {
let mut t = 0;
for i in 0..4 {
core::mem::swap(&mut t, &mut value[i]);
for i in 0..9 {
core::mem::swap(&mut t, &mut self.0[i]);
}
n -= 64;
n -= 29;
}

if n > 0 {
let mut t = 0;
#[allow(unused)]
for i in 0..4 {
let a = &mut value[i];
let t2 = *a >> (64 - n);
*a <<= n;
for i in 0..9 {
let a = &mut self.0[i];
let t2 = *a >> (29 - n);
*a = (*a << n) & MASK;
// *a <<= n;
*a |= t;
t = t2;
}
}
*self = Self::from_64x4(value)
}

#[inline]
#[ark_ff_asm::unroll_for_loops]
#[allow(unused)]
fn div2(&mut self) {
let mut value = self.to_64x4();
let mut t = 0;
for i in 0..4 {
let a = &mut value[4 - i - 1];
let t2 = *a << 63;
for i in 0..9 {
let a = &mut self.0[9 - i - 1];
let t2 = (*a << 28) & MASK;
*a >>= 1;
*a |= t;
t = t2;
}
*self = Self::from_64x4(value)
}

#[inline]
#[ark_ff_asm::unroll_for_loops]
fn divn(&mut self, mut n: u32) {
let mut value = self.to_64x4();

if n >= 64 * 4 {
*self = Self::from(0);
return;
}

while n >= 64 {
while n >= 29 {
let mut t = 0;
for i in 0..4 {
core::mem::swap(&mut t, &mut value[4 - i - 1]);
for i in 0..9 {
core::mem::swap(&mut t, &mut self.0[9 - i - 1]);
}
n -= 64;
n -= 29;
}

if n > 0 {
let mut t = 0;
#[allow(unused)]
for i in 0..4 {
let a = &mut value[4 - i - 1];
let t2 = *a << (64 - n);
for i in 0..9 {
let a = &mut self.0[9 - i - 1];
let t2 = (*a << (29 - n) & MASK);
// let t2 = *a << (29 - n);
*a >>= n;
*a |= t;
t = t2;
}
}

*self = Self::from_64x4(value)
}

#[inline]
Expand Down Expand Up @@ -226,12 +223,10 @@ impl BigInteger for BigInteger256 {
let mut res: [u64; 4] = <[u64; 4]>::default();
let mut acc: u64 = 0;

let mut bits = bits.to_vec();
bits.reverse();
for (i, bits64) in bits.chunks(64).enumerate() {
for bit in bits64.iter().rev() {
for (i, bits64) in bits.rchunks(64).enumerate() {
for bit in bits64.iter() {
acc <<= 1;
acc += *bit as u64;
acc |= *bit as u64;
}
res[i] = acc;
acc = 0;
Expand All @@ -243,11 +238,10 @@ impl BigInteger for BigInteger256 {
let mut res: [u64; 4] = <[u64; 4]>::default();
let mut acc: u64 = 0;

let bits = bits.to_vec();
for (i, bits64) in bits.chunks(64).enumerate() {
for bit in bits64.iter().rev() {
acc <<= 1;
acc += *bit as u64;
acc |= *bit as u64;
}
res[i] = acc;
acc = 0;
Expand Down
2 changes: 1 addition & 1 deletion ff/src/fields/models/webnode.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ impl<C: Fp256Parameters> core::convert::TryFrom<BigInteger256> for Fp256<C> {
}

const SHIFT: u32 = 29;
const MASK: u32 = (1 << SHIFT) - 1;
pub const MASK: u32 = (1 << SHIFT) - 1;

const SHIFT64: u64 = SHIFT as u64;
const MASK64: u64 = MASK as u64;
Expand Down

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