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adler32_simd.c
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adler32_simd.c
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/* adler32_simd.c
*
* Copyright 2017 The Chromium Authors
* Use of this source code is governed by a BSD-style license that can be
* found in the Chromium source repository LICENSE file.
*
* Per http://en.wikipedia.org/wiki/Adler-32 the adler32 A value (aka s1) is
* the sum of N input data bytes D1 ... DN,
*
* A = A0 + D1 + D2 + ... + DN
*
* where A0 is the initial value.
*
* SSE2 _mm_sad_epu8() can be used for byte sums (see http://bit.ly/2wpUOeD,
* for example) and accumulating the byte sums can use SSE shuffle-adds (see
* the "Integer" section of http://bit.ly/2erPT8t for details). Arm NEON has
* similar instructions.
*
* The adler32 B value (aka s2) sums the A values from each step:
*
* B0 + (A0 + D1) + (A0 + D1 + D2) + ... + (A0 + D1 + D2 + ... + DN) or
*
* B0 + N.A0 + N.D1 + (N-1).D2 + (N-2).D3 + ... + (N-(N-1)).DN
*
* B0 being the initial value. For 32 bytes (ideal for garden-variety SIMD):
*
* B = B0 + 32.A0 + [D1 D2 D3 ... D32] x [32 31 30 ... 1].
*
* Adjacent blocks of 32 input bytes can be iterated with the expressions to
* compute the adler32 s1 s2 of M >> 32 input bytes [1].
*
* As M grows, the s1 s2 sums grow. If left unchecked, they would eventually
* overflow the precision of their integer representation (bad). However, s1
* and s2 also need to be computed modulo the adler BASE value (reduced). If
* at most NMAX bytes are processed before a reduce, s1 s2 _cannot_ overflow
* a uint32_t type (the NMAX constraint) [2].
*
* [1] the iterative equations for s2 contain constant factors; these can be
* hoisted from the n-blocks do loop of the SIMD code.
*
* [2] zlib adler32_z() uses this fact to implement NMAX-block-based updates
* of the adler s1 s2 of uint32_t type (see adler32.c).
*/
#include "adler32_simd.h"
/* Definitions from adler32.c: largest prime smaller than 65536 */
#define BASE 65521U
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
#define NMAX 5552
#if defined(ADLER32_SIMD_SSSE3)
#include <tmmintrin.h>
uint32_t ZLIB_INTERNAL adler32_simd_( /* SSSE3 */
uint32_t adler,
const unsigned char *buf,
z_size_t len)
{
/*
* Split Adler-32 into component sums.
*/
uint32_t s1 = adler & 0xffff;
uint32_t s2 = adler >> 16;
/*
* Process the data in blocks.
*/
const unsigned BLOCK_SIZE = 1 << 5;
z_size_t blocks = len / BLOCK_SIZE;
len -= blocks * BLOCK_SIZE;
while (blocks)
{
unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */
if (n > blocks)
n = (unsigned) blocks;
blocks -= n;
const __m128i tap1 =
_mm_setr_epi8(32,31,30,29,28,27,26,25,24,23,22,21,20,19,18,17);
const __m128i tap2 =
_mm_setr_epi8(16,15,14,13,12,11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
const __m128i zero =
_mm_setr_epi8( 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
const __m128i ones =
_mm_set_epi16( 1, 1, 1, 1, 1, 1, 1, 1);
/*
* Process n blocks of data. At most NMAX data bytes can be
* processed before s2 must be reduced modulo BASE.
*/
__m128i v_ps = _mm_set_epi32(0, 0, 0, s1 * n);
__m128i v_s2 = _mm_set_epi32(0, 0, 0, s2);
__m128i v_s1 = _mm_set_epi32(0, 0, 0, 0);
do {
/*
* Load 32 input bytes.
*/
const __m128i bytes1 = _mm_loadu_si128((__m128i*)(buf));
const __m128i bytes2 = _mm_loadu_si128((__m128i*)(buf + 16));
/*
* Add previous block byte sum to v_ps.
*/
v_ps = _mm_add_epi32(v_ps, v_s1);
/*
* Horizontally add the bytes for s1, multiply-adds the
* bytes by [ 32, 31, 30, ... ] for s2.
*/
v_s1 = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes1, zero));
const __m128i mad1 = _mm_maddubs_epi16(bytes1, tap1);
v_s2 = _mm_add_epi32(v_s2, _mm_madd_epi16(mad1, ones));
v_s1 = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes2, zero));
const __m128i mad2 = _mm_maddubs_epi16(bytes2, tap2);
v_s2 = _mm_add_epi32(v_s2, _mm_madd_epi16(mad2, ones));
buf += BLOCK_SIZE;
} while (--n);
v_s2 = _mm_add_epi32(v_s2, _mm_slli_epi32(v_ps, 5));
/*
* Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
*/
#define S23O1 _MM_SHUFFLE(2,3,0,1) /* A B C D -> B A D C */
#define S1O32 _MM_SHUFFLE(1,0,3,2) /* A B C D -> C D A B */
v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S23O1));
v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S1O32));
s1 += _mm_cvtsi128_si32(v_s1);
v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S23O1));
v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S1O32));
s2 = _mm_cvtsi128_si32(v_s2);
#undef S23O1
#undef S1O32
/*
* Reduce.
*/
s1 %= BASE;
s2 %= BASE;
}
/*
* Handle leftover data.
*/
if (len) {
if (len >= 16) {
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
len -= 16;
}
while (len--) {
s2 += (s1 += *buf++);
}
if (s1 >= BASE)
s1 -= BASE;
s2 %= BASE;
}
/*
* Return the recombined sums.
*/
return s1 | (s2 << 16);
}
#elif defined(ADLER32_SIMD_NEON)
#include <arm_neon.h>
uint32_t ZLIB_INTERNAL adler32_simd_( /* NEON */
uint32_t adler,
const unsigned char *buf,
z_size_t len)
{
/*
* Split Adler-32 into component sums.
*/
uint32_t s1 = adler & 0xffff;
uint32_t s2 = adler >> 16;
/*
* Serially compute s1 & s2, until the data is 16-byte aligned.
*/
if ((uintptr_t)buf & 15) {
while ((uintptr_t)buf & 15) {
s2 += (s1 += *buf++);
--len;
}
if (s1 >= BASE)
s1 -= BASE;
s2 %= BASE;
}
/*
* Process the data in blocks.
*/
const unsigned BLOCK_SIZE = 1 << 5;
z_size_t blocks = len / BLOCK_SIZE;
len -= blocks * BLOCK_SIZE;
while (blocks)
{
unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */
if (n > blocks)
n = (unsigned) blocks;
blocks -= n;
/*
* Process n blocks of data. At most NMAX data bytes can be
* processed before s2 must be reduced modulo BASE.
*/
uint32x4_t v_s2 = (uint32x4_t) { 0, 0, 0, s1 * n };
uint32x4_t v_s1 = (uint32x4_t) { 0, 0, 0, 0 };
uint16x8_t v_column_sum_1 = vdupq_n_u16(0);
uint16x8_t v_column_sum_2 = vdupq_n_u16(0);
uint16x8_t v_column_sum_3 = vdupq_n_u16(0);
uint16x8_t v_column_sum_4 = vdupq_n_u16(0);
do {
/*
* Load 32 input bytes.
*/
const uint8x16_t bytes1 = vld1q_u8((uint8_t*)(buf));
const uint8x16_t bytes2 = vld1q_u8((uint8_t*)(buf + 16));
/*
* Add previous block byte sum to v_s2.
*/
v_s2 = vaddq_u32(v_s2, v_s1);
/*
* Horizontally add the bytes for s1.
*/
v_s1 = vpadalq_u16(v_s1, vpadalq_u8(vpaddlq_u8(bytes1), bytes2));
/*
* Vertically add the bytes for s2.
*/
v_column_sum_1 = vaddw_u8(v_column_sum_1, vget_low_u8 (bytes1));
v_column_sum_2 = vaddw_u8(v_column_sum_2, vget_high_u8(bytes1));
v_column_sum_3 = vaddw_u8(v_column_sum_3, vget_low_u8 (bytes2));
v_column_sum_4 = vaddw_u8(v_column_sum_4, vget_high_u8(bytes2));
buf += BLOCK_SIZE;
} while (--n);
v_s2 = vshlq_n_u32(v_s2, 5);
/*
* Multiply-add bytes by [ 32, 31, 30, ... ] for s2.
*/
v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_1),
(uint16x4_t) { 32, 31, 30, 29 });
v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_1),
(uint16x4_t) { 28, 27, 26, 25 });
v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_2),
(uint16x4_t) { 24, 23, 22, 21 });
v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_2),
(uint16x4_t) { 20, 19, 18, 17 });
v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_3),
(uint16x4_t) { 16, 15, 14, 13 });
v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_3),
(uint16x4_t) { 12, 11, 10, 9 });
v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_4),
(uint16x4_t) { 8, 7, 6, 5 });
v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_4),
(uint16x4_t) { 4, 3, 2, 1 });
/*
* Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
*/
uint32x2_t sum1 = vpadd_u32(vget_low_u32(v_s1), vget_high_u32(v_s1));
uint32x2_t sum2 = vpadd_u32(vget_low_u32(v_s2), vget_high_u32(v_s2));
uint32x2_t s1s2 = vpadd_u32(sum1, sum2);
s1 += vget_lane_u32(s1s2, 0);
s2 += vget_lane_u32(s1s2, 1);
/*
* Reduce.
*/
s1 %= BASE;
s2 %= BASE;
}
/*
* Handle leftover data.
*/
if (len) {
if (len >= 16) {
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
s2 += (s1 += *buf++);
len -= 16;
}
while (len--) {
s2 += (s1 += *buf++);
}
if (s1 >= BASE)
s1 -= BASE;
s2 %= BASE;
}
/*
* Return the recombined sums.
*/
return s1 | (s2 << 16);
}
#endif /* ADLER32_SIMD_SSSE3 */