saymrwulf/risc0-curve25519-dalek-source
1
0
Fork 0
mirror of https://github.com/saymrwulf/risc0-curve25519-dalek-source.git synced 2026-09-05 20:10:35 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

Use >> instead of srl intrinsic

Browse source
This commit is contained in:
Henry de Valence 2018-01-03 14:04:27 -08:00
parent 4cbff3983d
commit f816083575
1 changed files with 5 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
src/backend/avx2/field.rs
View file

@ -296,25 +296,16 @@ impl FieldElement32x4 {
let LOW_25_BITS: u64x4 = u64x4::splat((1<<25)-1);
let LOW_26_BITS: u64x4 = u64x4::splat((1<<26)-1);
/// XXX check whether u64x4 >> is this already
#[inline(always)]
fn shift_right(x: u64x4, s: i32) -> u64x4 {
unsafe {
use stdsimd::vendor::_mm256_srli_epi64;
_mm256_srli_epi64(x.into(), s).as_u64x4()
}
}
// Carry the value from limb i = 0..8 to limb i+1
let carry = |z: &mut [u64x4; 10], i: usize| {
debug_assert!(i < 9);
if i % 2 == 0 {
// Even limbs have 26 bits
z[i+1] = z[i+1] + shift_right(z[i], 26);
z[i+1] = z[i+1] + (z[i] >> 26);
z[i] = z[i] & LOW_26_BITS;
} else {
// Odd limbs have 25 bits
z[i+1] = z[i+1] + shift_right(z[i], 25);
z[i+1] = z[i+1] + (z[i] >> 25);
z[i] = z[i] & LOW_25_BITS;
}
};
@ -337,10 +328,10 @@ impl FieldElement32x4 {
// big. To ensure c < 2^32, we would need z[9] < 2^57.
// Instead, we split the carry in two, with c = c_0 + c_1*2^26.
let c = shift_right(z[9], 25);
let c = z[9] >> 25;
z[9] = z[9] & LOW_25_BITS;
let mut c0 = c & LOW_26_BITS; // c0 < 2^26;
let mut c1 = shift_right(c, 26); // c1 < 2^(39-26) = 2^13;
let mut c0 = c & LOW_26_BITS; // c0 < 2^26;
let mut c1 = c >> 26; // c1 < 2^(39-26) = 2^13;
unsafe {
use stdsimd::vendor::_mm256_mul_epu32;