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https://github.com/logos-storage/plonky2.git
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2ae9e34993
* AVX2 vectorization of Poseidon constant layer * Silence unused import warning + minor style * Daniel comment
223 lines
8.4 KiB
Rust
223 lines
8.4 KiB
Rust
use core::arch::x86_64::*;
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use crate::field::crandall_field::CrandallField;
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use crate::field::field_types::PrimeField;
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use crate::field::packed_avx2::PackedCrandallAVX2;
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use crate::field::packed_field::PackedField;
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const EPSILON: u64 = 0u64.wrapping_sub(CrandallField::ORDER);
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const SIGN_BIT: u64 = 1 << 63;
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const MDS_MATRIX_EXPS8: [i32; 8] = [2, 0, 1, 8, 4, 3, 0, 0];
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const MDS_MATRIX_EXPS12: [i32; 12] = [10, 13, 2, 0, 4, 1, 8, 7, 15, 5, 0, 0];
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/// Pair of vectors (hi, lo) representing a u128.
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type Vecs128 = (__m256i, __m256i);
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/// Takes cumul (u128) and x (u64). Returns cumul + (x << SHIFT) as u128.
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/// Assumes that cumul is shifted by 1 << 63; the result is similarly shifted.
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#[inline(always)]
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unsafe fn shift_and_accumulate<const SHIFT: i32>(
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x: __m256i,
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(hi_cumul, lo_cumul_s): Vecs128,
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) -> Vecs128
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where
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[(); (64 - SHIFT) as usize]: ,
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{
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let x_shifted_lo = _mm256_slli_epi64::<SHIFT>(x);
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let x_shifted_hi = _mm256_srli_epi64::<{ 64 - SHIFT }>(x);
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let res_lo_s = _mm256_add_epi64(lo_cumul_s, x_shifted_lo);
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let carry = _mm256_cmpgt_epi64(lo_cumul_s, res_lo_s);
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let res_hi = _mm256_sub_epi64(_mm256_add_epi64(hi_cumul, x_shifted_hi), carry);
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(res_hi, res_lo_s)
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}
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/// Extract state[OFFSET..OFFSET + 4] as a vector. Wraps around the boundary.
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#[inline(always)]
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unsafe fn get_vector_with_offset<const WIDTH: usize, const OFFSET: usize>(
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state: [CrandallField; WIDTH],
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) -> __m256i {
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_mm256_setr_epi64x(
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state[OFFSET % WIDTH].0 as i64,
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state[(OFFSET + 1) % WIDTH].0 as i64,
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state[(OFFSET + 2) % WIDTH].0 as i64,
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state[(OFFSET + 3) % WIDTH].0 as i64,
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)
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}
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/// Extract CrandallField element from vector.
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#[inline(always)]
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unsafe fn extract<const INDEX: i32>(v: __m256i) -> CrandallField {
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CrandallField(_mm256_extract_epi64::<INDEX>(v) as u64)
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}
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#[inline(always)]
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unsafe fn iteration8<const INDEX: usize, const SHIFT: i32>(
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[cumul0_s, cumul1_s]: [Vecs128; 2],
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state: [CrandallField; 8],
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) -> [Vecs128; 2]
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// 2 vectors of 4 needed to represent entire state.
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where
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[(); INDEX + 4]: ,
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[(); (64 - SHIFT) as usize]: ,
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{
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// Entire state, rotated by INDEX.
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let state0 = get_vector_with_offset::<8, INDEX>(state);
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let state1 = get_vector_with_offset::<8, { INDEX + 4 }>(state);
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[
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shift_and_accumulate::<SHIFT>(state0, cumul0_s),
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shift_and_accumulate::<SHIFT>(state1, cumul1_s),
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]
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}
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#[inline(always)]
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pub fn crandall_poseidon8_mds_avx2(state: [CrandallField; 8]) -> [CrandallField; 8] {
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unsafe {
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let mut res_s = [(_mm256_setzero_si256(), _mm256_set1_epi64x(SIGN_BIT as i64)); 2];
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// The scalar loop goes:
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// for r in 0..WIDTH {
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// let mut res = 0u128;
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// for i in 0..WIDTH {
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// res += (state[(i + r) % WIDTH] as u128) << MDS_MATRIX_EXPS[i];
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// }
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// result[r] = reduce(res);
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// }
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//
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// Here, we swap the loops. Equivalent to:
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// let mut res = [0u128; WIDTH];
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// for i in 0..WIDTH {
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// let mds_matrix_exp = MDS_MATRIX_EXPS[i];
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// for r in 0..WIDTH {
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// res[r] += (state[(i + r) % WIDTH] as u128) << mds_matrix_exp;
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// }
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// }
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// for r in 0..WIDTH {
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// result[r] = reduce(res[r]);
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// }
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//
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// Notice that that in the lower version, all iterations of the inner loop shift by the same
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// amount. In vector, we perform multiple iterations of the loop at once, and vector shifts
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// are cheaper when all elements are shifted by the same amount.
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res_s = iteration8::<0, { MDS_MATRIX_EXPS8[0] }>(res_s, state);
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res_s = iteration8::<1, { MDS_MATRIX_EXPS8[1] }>(res_s, state);
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res_s = iteration8::<2, { MDS_MATRIX_EXPS8[2] }>(res_s, state);
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res_s = iteration8::<3, { MDS_MATRIX_EXPS8[3] }>(res_s, state);
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res_s = iteration8::<4, { MDS_MATRIX_EXPS8[4] }>(res_s, state);
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res_s = iteration8::<5, { MDS_MATRIX_EXPS8[5] }>(res_s, state);
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res_s = iteration8::<6, { MDS_MATRIX_EXPS8[6] }>(res_s, state);
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res_s = iteration8::<7, { MDS_MATRIX_EXPS8[7] }>(res_s, state);
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let [res0_s, res1_s] = res_s;
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let reduced0 = reduce96s(res0_s);
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let reduced1 = reduce96s(res1_s);
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[
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extract::<0>(reduced0),
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extract::<1>(reduced0),
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extract::<2>(reduced0),
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extract::<3>(reduced0),
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extract::<0>(reduced1),
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extract::<1>(reduced1),
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extract::<2>(reduced1),
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extract::<3>(reduced1),
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]
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}
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}
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#[inline(always)]
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unsafe fn iteration12<const INDEX: usize, const SHIFT: i32>(
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[cumul0_s, cumul1_s, cumul2_s]: [Vecs128; 3],
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state: [CrandallField; 12],
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) -> [Vecs128; 3]
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// 3 vectors of 4 needed to represent entire state.
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where
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[(); INDEX + 4]: ,
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[(); INDEX + 8]: ,
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[(); (64 - SHIFT) as usize]: ,
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{
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// Entire state, rotated by INDEX.
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let state0 = get_vector_with_offset::<12, INDEX>(state);
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let state1 = get_vector_with_offset::<12, { INDEX + 4 }>(state);
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let state2 = get_vector_with_offset::<12, { INDEX + 8 }>(state);
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[
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shift_and_accumulate::<SHIFT>(state0, cumul0_s),
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shift_and_accumulate::<SHIFT>(state1, cumul1_s),
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shift_and_accumulate::<SHIFT>(state2, cumul2_s),
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]
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}
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#[inline(always)]
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pub fn crandall_poseidon12_mds_avx2(state: [CrandallField; 12]) -> [CrandallField; 12] {
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unsafe {
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let mut res_s = [(_mm256_setzero_si256(), _mm256_set1_epi64x(SIGN_BIT as i64)); 3];
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// See width-8 version for explanation.
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res_s = iteration12::<0, { MDS_MATRIX_EXPS12[0] }>(res_s, state);
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res_s = iteration12::<1, { MDS_MATRIX_EXPS12[1] }>(res_s, state);
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res_s = iteration12::<2, { MDS_MATRIX_EXPS12[2] }>(res_s, state);
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res_s = iteration12::<3, { MDS_MATRIX_EXPS12[3] }>(res_s, state);
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res_s = iteration12::<4, { MDS_MATRIX_EXPS12[4] }>(res_s, state);
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res_s = iteration12::<5, { MDS_MATRIX_EXPS12[5] }>(res_s, state);
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res_s = iteration12::<6, { MDS_MATRIX_EXPS12[6] }>(res_s, state);
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res_s = iteration12::<7, { MDS_MATRIX_EXPS12[7] }>(res_s, state);
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res_s = iteration12::<8, { MDS_MATRIX_EXPS12[8] }>(res_s, state);
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res_s = iteration12::<9, { MDS_MATRIX_EXPS12[9] }>(res_s, state);
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res_s = iteration12::<10, { MDS_MATRIX_EXPS12[10] }>(res_s, state);
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res_s = iteration12::<11, { MDS_MATRIX_EXPS12[11] }>(res_s, state);
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let [res0_s, res1_s, res2_s] = res_s;
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let reduced0 = reduce96s(res0_s);
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let reduced1 = reduce96s(res1_s);
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let reduced2 = reduce96s(res2_s);
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[
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extract::<0>(reduced0),
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extract::<1>(reduced0),
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extract::<2>(reduced0),
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extract::<3>(reduced0),
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extract::<0>(reduced1),
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extract::<1>(reduced1),
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extract::<2>(reduced1),
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extract::<3>(reduced1),
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extract::<0>(reduced2),
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extract::<1>(reduced2),
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extract::<2>(reduced2),
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extract::<3>(reduced2),
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]
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}
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}
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#[inline(always)]
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unsafe fn reduce96s(x_s: Vecs128) -> __m256i {
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let (hi0, lo0_s) = x_s;
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let lo1 = _mm256_mul_epu32(hi0, _mm256_set1_epi64x(EPSILON as i64));
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add_no_canonicalize_64_64s(lo1, lo0_s)
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}
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#[inline(always)]
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unsafe fn add_no_canonicalize_64_64s(x: __m256i, y_s: __m256i) -> __m256i {
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let res_wrapped_s = _mm256_add_epi64(x, y_s);
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let mask = _mm256_cmpgt_epi64(y_s, res_wrapped_s);
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let res_wrapped = _mm256_xor_si256(res_wrapped_s, _mm256_set1_epi64x(SIGN_BIT as i64));
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let wrapback_amt = _mm256_and_si256(mask, _mm256_set1_epi64x(EPSILON as i64));
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let res = _mm256_add_epi64(res_wrapped, wrapback_amt);
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res
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}
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/// Poseidon constant layer for Crandall. Assumes that every element in round_constants is in
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/// 0..CrandallField::ORDER; when this is not true it may return garbage. It's marked unsafe for
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/// this reason.
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#[inline(always)]
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pub unsafe fn crandall_poseidon_const_avx2<const PACKED_WIDTH: usize>(
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state: &mut [CrandallField; 4 * PACKED_WIDTH],
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round_constants: [u64; 4 * PACKED_WIDTH],
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) {
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let packed_state = PackedCrandallAVX2::pack_slice_mut(state);
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let packed_round_constants =
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std::slice::from_raw_parts((&round_constants).as_ptr().cast::<__m256i>(), PACKED_WIDTH);
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for i in 0..PACKED_WIDTH {
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packed_state[i] = packed_state[i].add_canonical_u64(packed_round_constants[i]);
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}
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}
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