mirror of https://git.tukaani.org/xz.git
liblzma: Added crc32_clmul to crc32_fast.c.
This commit is contained in:
Hans Jansen
Jia Tan
parent
93e6fb08b2
commit
f1cd9d7194
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@ -3,13 +3,28 @@
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/// \file crc32.c
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/// \brief CRC32 calculation
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///
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/// Calculate the CRC32 using the slice-by-eight algorithm.
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/// There are two methods in this file.
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/// crc32_generic uses the slice-by-eight algorithm.
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/// It is explained in this document:
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/// http://www.intel.com/technology/comms/perfnet/download/CRC_generators.pdf
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/// The code in this file is not the same as in Intel's paper, but
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/// the basic principle is identical.
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///
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/// crc32_clmul uses 32/64-bit x86 SSSE3, SSE4.1, and CLMUL instructions.
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/// It was derived from
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/// https://www.researchgate.net/publication/263424619_Fast_CRC_computation
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/// and the public domain code from https://github.com/rawrunprotected/crc
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/// (URLs were checked on 2023-09-29).
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///
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/// FIXME: Builds for 32-bit x86 use crc32_x86.S by default instead
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/// of this file and thus CLMUL version isn't available on 32-bit x86
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/// unless configured with --disable-assembler. Even then the lookup table
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/// isn't omitted in crc32_table.c since it doesn't know that assembly
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/// code has been disabled.
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//
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// Author: Lasse Collin
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// Authors: Lasse Collin
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// Ilya Kurdyukov
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// Hans Jansen
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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@ -19,12 +34,14 @@
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#include "check.h"
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#include "crc_common.h"
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///////////////////
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// Generic CRC32 //
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///////////////////
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#ifdef CRC_GENERIC
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// If you make any changes, do some benchmarking! Seemingly unrelated
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// changes can very easily ruin the performance (and very probably is
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// very compiler dependent).
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extern LZMA_API(uint32_t)
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lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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static uint32_t
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crc32_generic(const uint8_t *buf, size_t size, uint32_t crc)
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{
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crc = ~crc;
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@ -80,3 +97,219 @@ lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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return ~crc;
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}
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#endif
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/////////////////////
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// x86 CLMUL CRC32 //
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/////////////////////
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#ifdef CRC_CLMUL
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#include <immintrin.h>
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/*
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// These functions were used to generate the constants
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// at the top of crc32_clmul().
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static uint64_t
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calc_lo(uint64_t p, uint64_t a, int n)
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{
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uint64_t b = 0; int i;
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for (i = 0; i < n; i++) {
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b = b >> 1 | (a & 1) << (n - 1);
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a = (a >> 1) ^ ((0 - (a & 1)) & p);
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}
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return b;
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}
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// same as ~crc(&a, sizeof(a), ~0)
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static uint64_t
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calc_hi(uint64_t p, uint64_t a, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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a = (a >> 1) ^ ((0 - (a & 1)) & p);
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return a;
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}
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*/
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// MSVC (VS2015 - VS2022) produces bad 32-bit x86 code from the CLMUL CRC
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// code when optimizations are enabled (release build). According to the bug
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// report, the ebx register is corrupted and the calculated result is wrong.
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// Trying to workaround the problem with "__asm mov ebx, ebx" didn't help.
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// The following pragma works and performance is still good. x86-64 builds
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// aren't affected by this problem.
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//
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// NOTE: Another pragma after the function restores the optimizations.
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// If the #if condition here is updated, the other one must be updated too.
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#if defined(_MSC_VER) && !defined(__INTEL_COMPILER) && !defined(__clang__) \
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&& defined(_M_IX86)
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# pragma optimize("g", off)
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#endif
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// EDG-based compilers (Intel's classic compiler and compiler for E2K) can
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// define __GNUC__ but the attribute must not be used with them.
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// The new Clang-based ICX needs the attribute.
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//
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// NOTE: Build systems check for this too, keep them in sync with this.
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#if (defined(__GNUC__) || defined(__clang__)) && !defined(__EDG__)
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__attribute__((__target__("ssse3,sse4.1,pclmul")))
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#endif
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static uint32_t
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crc32_clmul(const uint8_t *buf, size_t size, uint32_t crc)
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{
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// The prototypes of the intrinsics use signed types while most of
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// the values are treated as unsigned here. These warnings in this
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// function have been checked and found to be harmless so silence them.
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#if TUKLIB_GNUC_REQ(4, 6) || defined(__clang__)
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# pragma GCC diagnostic push
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# pragma GCC diagnostic ignored "-Wsign-conversion"
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# pragma GCC diagnostic ignored "-Wconversion"
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#endif
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#ifndef CRC_USE_GENERIC_FOR_SMALL_INPUTS
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// The code assumes that there is at least one byte of input.
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if (size == 0)
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return crc;
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#endif
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// uint32_t poly = 0xedb88320;
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uint64_t p = 0x1db710640; // p << 1
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uint64_t mu = 0x1f7011641; // calc_lo(p, p, 32) << 1 | 1
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uint64_t k5 = 0x163cd6124; // calc_hi(p, p, 32) << 1
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uint64_t k4 = 0x0ccaa009e; // calc_hi(p, p, 64) << 1
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uint64_t k3 = 0x1751997d0; // calc_hi(p, p, 128) << 1
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__m128i vfold4 = _mm_set_epi64x(mu, p);
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__m128i vfold8 = _mm_set_epi64x(0, k5);
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__m128i vfold16 = _mm_set_epi64x(k4, k3);
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__m128i v0, v1, v2;
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crc_simd_body(buf, size, &v0, &v1, vfold16, _mm_cvtsi32_si128(~crc));
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v1 = _mm_xor_si128(
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_mm_clmulepi64_si128(v0, vfold16, 0x10), v1); // xxx0
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v2 = _mm_shuffle_epi32(v1, 0xe7); // 0xx0
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v0 = _mm_slli_epi64(v1, 32); // [0]
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v0 = _mm_clmulepi64_si128(v0, vfold8, 0x00);
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v0 = _mm_xor_si128(v0, v2); // [1] [2]
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v2 = _mm_clmulepi64_si128(v0, vfold4, 0x10);
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v2 = _mm_clmulepi64_si128(v2, vfold4, 0x00);
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v0 = _mm_xor_si128(v0, v2); // [2]
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return ~_mm_extract_epi32(v0, 2);
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#if TUKLIB_GNUC_REQ(4, 6) || defined(__clang__)
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# pragma GCC diagnostic pop
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#endif
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}
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#if defined(_MSC_VER) && !defined(__INTEL_COMPILER) && !defined(__clang__) \
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&& defined(_M_IX86)
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# pragma optimize("", on)
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#endif
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#endif
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#if defined(CRC_GENERIC) && defined(CRC_CLMUL)
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typedef uint32_t (*crc32_func_type)(
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const uint8_t *buf, size_t size, uint32_t crc);
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// Clang 16.0.0 and older has a bug where it marks the ifunc resolver
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// function as unused since it is static and never used outside of
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// __attribute__((__ifunc__())).
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#if defined(HAVE_FUNC_ATTRIBUTE_IFUNC) && defined(__clang__)
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# pragma GCC diagnostic push
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# pragma GCC diagnostic ignored "-Wunused-function"
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#endif
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static crc32_func_type
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crc32_resolve(void)
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{
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return is_clmul_supported() ? &crc32_clmul : &crc32_generic;
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}
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#if defined(HAVE_FUNC_ATTRIBUTE_IFUNC) && defined(__clang__)
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# pragma GCC diagnostic pop
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#endif
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#ifndef HAVE_FUNC_ATTRIBUTE_IFUNC
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#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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# define CRC32_SET_FUNC_ATTR __attribute__((__constructor__))
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static crc32_func_type crc32_func;
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#else
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# define CRC32_SET_FUNC_ATTR
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static uint32_t crc32_dispatch(const uint8_t *buf, size_t size, uint32_t crc);
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static crc32_func_type crc32_func = &crc32_dispatch;
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#endif
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CRC32_SET_FUNC_ATTR
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static void
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crc32_set_func(void)
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{
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crc32_func = crc32_resolve();
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return;
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}
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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static uint32_t
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crc32_dispatch(const uint8_t *buf, size_t size, uint32_t crc)
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{
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// When __attribute__((__ifunc__(...))) and
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// __attribute__((__constructor__)) isn't supported, set the
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// function pointer without any locking. If multiple threads run
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// the detection code in parallel, they will all end up setting
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// the pointer to the same value. This avoids the use of
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// mythread_once() on every call to lzma_crc32() but this likely
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// isn't strictly standards compliant. Let's change it if it breaks.
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crc32_set_func();
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return crc32_func(buf, size, crc);
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}
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#endif
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#endif
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#endif
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#if defined(CRC_GENERIC) && defined(CRC_CLMUL) \
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&& defined(HAVE_FUNC_ATTRIBUTE_IFUNC)
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extern LZMA_API(uint32_t)
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lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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__attribute__((__ifunc__("crc32_resolve")));
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#else
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extern LZMA_API(uint32_t)
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lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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{
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#if defined(CRC_GENERIC) && defined(CRC_CLMUL)
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// If CLMUL is available, it is the best for non-tiny inputs,
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// being over twice as fast as the generic slice-by-four version.
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// However, for size <= 16 it's different. In the extreme case
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// of size == 1 the generic version can be five times faster.
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// At size >= 8 the CLMUL starts to become reasonable. It
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// varies depending on the alignment of buf too.
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//
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// The above doesn't include the overhead of mythread_once().
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// At least on x86-64 GNU/Linux, pthread_once() is very fast but
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// it still makes lzma_crc32(buf, 1, crc) 50-100 % slower. When
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// size reaches 12-16 bytes the overhead becomes negligible.
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//
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// So using the generic version for size <= 16 may give better
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// performance with tiny inputs but if such inputs happen rarely
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// it's not so obvious because then the lookup table of the
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// generic version may not be in the processor cache.
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#ifdef CRC_USE_GENERIC_FOR_SMALL_INPUTS
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if (size <= 16)
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return crc32_generic(buf, size, crc);
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#endif
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return crc32_func(buf, size, crc);
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#elif defined(CRC_CLMUL)
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return crc32_clmul(buf, size, crc);
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#else
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return crc32_generic(buf, size, crc);
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#endif
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}
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#endif
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@ -12,11 +12,22 @@
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#include "common.h"
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// FIXME: Compared to crc32_fast.c this has to check for __x86_64__ too
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// so that in 32-bit builds crc32_x86.S won't break due to a missing table.
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#if !defined(HAVE_ENCODERS) && ((defined(__x86_64__) && defined(__SSSE3__) \
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&& defined(__SSE4_1__) && defined(__PCLMUL__)) \
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|| (defined(__e2k__) && __iset__ >= 6))
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// No table needed. Use a typedef to avoid an empty translation unit.
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typedef void lzma_crc32_dummy;
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#else
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// Having the declaration here silences clang -Wmissing-variable-declarations.
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extern const uint32_t lzma_crc32_table[8][256];
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#ifdef WORDS_BIGENDIAN
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# include "crc32_table_be.h"
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#else
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# include "crc32_table_le.h"
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# ifdef WORDS_BIGENDIAN
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# include "crc32_table_be.h"
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# else
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# include "crc32_table_le.h"
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# endif
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#endif
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