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/* insert_string.h
*
* Copyright 2019 The Chromium Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the Chromium source repository LICENSE file.
*/
#ifdef _MSC_VER
#define INLINE __inline
#else
#define INLINE inline
#endif
#include "cpu_features.h"
/* Optimized insert_string block */
#if defined(CRC32_SIMD_SSE42_PCLMUL) || defined(CRC32_ARMV8_CRC32)
#define TARGET_CPU_WITH_CRC
// clang-format off
#if defined(CRC32_SIMD_SSE42_PCLMUL)
/* Required to make MSVC bot build pass. */
#include <smmintrin.h>
#if defined(__GNUC__) || defined(__clang__)
#undef TARGET_CPU_WITH_CRC
#define TARGET_CPU_WITH_CRC __attribute__((target("sse4.2")))
#endif
#define _cpu_crc32_u32 _mm_crc32_u32
#elif defined(CRC32_ARMV8_CRC32)
#if defined(__clang__)
#undef TARGET_CPU_WITH_CRC
#define __crc32cw __builtin_arm_crc32cw
#endif
#define _cpu_crc32_u32 __crc32cw
#if defined(__aarch64__)
#define TARGET_CPU_WITH_CRC __attribute__((target("crc")))
#else // !defined(__aarch64__)
#define TARGET_CPU_WITH_CRC __attribute__((target("armv8-a,crc")))
#endif // defined(__aarch64__)
#endif
// clang-format on
TARGET_CPU_WITH_CRC
local INLINE Pos insert_string_optimized(deflate_state* const s,
const Pos str) {
Pos ret;
unsigned *ip, val, h = 0;
ip = (unsigned*)&s->window[str];
val = *ip;
if (s->level >= 6)
val &= 0xFFFFFF;
/* Unlike the case of data integrity checks for GZIP format where the
* polynomial used is defined (https://tools.ietf.org/html/rfc1952#page-11),
* here it is just a hash function for the hash table used while
* performing compression.
*/
h = _cpu_crc32_u32(h, val);
ret = s->head[h & s->hash_mask];
s->head[h & s->hash_mask] = str;
s->prev[str & s->w_mask] = ret;
return ret;
}
#endif /* Optimized insert_string block */
/* ===========================================================================
* Update a hash value with the given input byte
* IN assertion: all calls to UPDATE_HASH are made with consecutive input
* characters, so that a running hash key can be computed from the previous
* key instead of complete recalculation each time.
*/
#define UPDATE_HASH(s, h, c) (h = (((h) << s->hash_shift) ^ (c)) & s->hash_mask)
/* ===========================================================================
* Insert string str in the dictionary and set match_head to the previous head
* of the hash chain (the most recent string with same hash key). Return
* the previous length of the hash chain.
* If this file is compiled with -DFASTEST, the compression level is forced
* to 1, and no hash chains are maintained.
* IN assertion: all calls to INSERT_STRING are made with consecutive input
* characters and the first MIN_MATCH bytes of str are valid (except for
* the last MIN_MATCH-1 bytes of the input file).
*/
local INLINE Pos insert_string_c(deflate_state* const s, const Pos str) {
Pos ret;
UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH - 1)]);
#ifdef FASTEST
ret = s->head[s->ins_h];
#else
ret = s->prev[str & s->w_mask] = s->head[s->ins_h];
#endif
s->head[s->ins_h] = str;
return ret;
}
local INLINE Pos insert_string(deflate_state* const s, const Pos str) {
/* String dictionary insertion: faster symbol hashing has a positive impact
* on data compression speeds (around 20% on Intel and 36% on Arm Cortex big
* cores).
* A misfeature is that the generated compressed output will differ from
* vanilla zlib (even though it is still valid 'DEFLATE-d' content).
*
* We offer here a way to disable the optimization if there is the expectation
* that compressed content should match when compared to vanilla zlib.
*/
#if !defined(CHROMIUM_ZLIB_NO_CASTAGNOLI)
/* TODO(cavalcantii): unify CPU features code. */
#if defined(CRC32_ARMV8_CRC32)
if (arm_cpu_enable_crc32)
return insert_string_optimized(s, str);
#elif defined(CRC32_SIMD_SSE42_PCLMUL)
if (x86_cpu_enable_simd)
return insert_string_optimized(s, str);
#endif
#endif
return insert_string_c(s, str);
}
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