tornado-packages/phase2-bn254
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Introduce expose-arith unstable feature for exposing arithmetic functions downstream.

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This commit is contained in:
Sean Bowe 2017-12-04 21:47:45 -07:00
parent cc8be5b780
commit 04a32fb443
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GPG Key ID: 95684257D8F8B031
2 changed files with 21 additions and 10 deletions
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3
Cargo.toml
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@ -17,6 +17,7 @@ byteorder = "1"
clippy = { version = "0.0.174", optional = true }
[features]
unstable-features = []
unstable-features = ["expose-arith"]
expose-arith = []
u128-support = []
default = []

28
src/lib.rs
View File

@ -613,14 +613,18 @@ fn test_bit_iterator() {
assert!(a.next().is_none());
}
use self::arith::*;
#[cfg(not(feature = "expose-arith"))]
use self::arith_impl::*;
#[cfg(feature = "expose-arith")]
pub use self::arith_impl::*;
#[cfg(feature = "u128-support")]
mod arith {
mod arith_impl {
/// Calculate a - b - borrow, returning the result and modifying
/// the borrow value.
#[inline(always)]
pub(crate) fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
pub fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
let tmp = (1u128 << 64) + u128::from(a) - u128::from(b) - u128::from(*borrow);
*borrow = if tmp >> 64 == 0 { 1 } else { 0 };
@ -631,7 +635,7 @@ mod arith {
/// Calculate a + b + carry, returning the sum and modifying the
/// carry value.
#[inline(always)]
pub(crate) fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
pub fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
let tmp = u128::from(a) + u128::from(b) + u128::from(*carry);
*carry = (tmp >> 64) as u64;
@ -642,7 +646,7 @@ mod arith {
/// Calculate a + (b * c) + carry, returning the least significant digit
/// and setting carry to the most significant digit.
#[inline(always)]
pub(crate) fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
pub fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
let tmp = (u128::from(a)) + u128::from(b) * u128::from(c) + u128::from(*carry);
*carry = (tmp >> 64) as u64;
@ -652,7 +656,7 @@ mod arith {
}
#[cfg(not(feature = "u128-support"))]
mod arith {
mod arith_impl {
#[inline(always)]
fn split_u64(i: u64) -> (u64, u64) {
(i >> 32, i & 0xFFFFFFFF)
@ -663,8 +667,10 @@ mod arith {
(hi << 32) | lo
}
/// Calculate a - b - borrow, returning the result and modifying
/// the borrow value.
#[inline(always)]
pub(crate) fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
pub fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
let (a_hi, a_lo) = split_u64(a);
let (b_hi, b_lo) = split_u64(b);
let (b, r0) = split_u64((1 << 32) + a_lo - b_lo - *borrow);
@ -675,8 +681,10 @@ mod arith {
combine_u64(r1, r0)
}
/// Calculate a + b + carry, returning the sum and modifying the
/// carry value.
#[inline(always)]
pub(crate) fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
pub fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
let (a_hi, a_lo) = split_u64(a);
let (b_hi, b_lo) = split_u64(b);
let (carry_hi, carry_lo) = split_u64(*carry);
@ -689,8 +697,10 @@ mod arith {
combine_u64(r1, r0)
}
/// Calculate a + (b * c) + carry, returning the least significant digit
/// and setting carry to the most significant digit.
#[inline(always)]
pub(crate) fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
pub fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
/*
[ b_hi | b_lo ]
[ c_hi | c_lo ] *