mirror of https://git.tukaani.org/xz.git
liblzma: Add fast CRC64 for 32/64-bit x86 using SSSE3 + SSE4.1 + CLMUL.
It also works on E2K as it supports these intrinsics. On x86-64 runtime detection is used so the code keeps working on older processors too. A CLMUL-only build can be done by using -msse4.1 -mpclmul in CFLAGS and this will reduce the library size since the generic implementation and its 8 KiB lookup table will be omitted. On 32-bit x86 this isn't used by default for now because by default on 32-bit x86 the separate assembly file crc64_x86.S is used. If --disable-assembler is used then this new CLMUL code is used the same way as on 64-bit x86. However, a CLMUL-only build (-msse4.1 -mpclmul) won't omit the 8 KiB lookup table on 32-bit x86 due to a currently-missing check for disabled assembler usage. The configure.ac check should be such that the code won't be built if something in the toolchain doesn't support it but --disable-clmul-crc option can be used to unconditionally disable this feature. CLMUL speeds up decompression of files that have compressed very well (assuming CRC64 is used as a check type). It is know that the CLMUL code is significantly slower than the generic code for tiny inputs (especially 1-8 bytes but up to 16 bytes). If that is a real-world problem then there is already a commented-out variant that uses the generic version for small inputs. Thanks to Ilya Kurdyukov for the original patch which was derived from a white paper from Intel [1] (published in 2009) and public domain code from [2] (released in 2016). [1] https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf [2] https://github.com/rawrunprotected/crc
This commit is contained in:
Lasse Collin
parent
3b466bc796
commit
f644473a21
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@ -49,8 +49,10 @@
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cmake_minimum_required(VERSION 3.13...3.16 FATAL_ERROR)
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include(CMakePushCheckState)
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include(CheckIncludeFile)
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include(CheckSymbolExists)
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include(CheckStructHasMember)
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include(CheckCSourceCompiles)
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include(cmake/tuklib_integer.cmake)
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include(cmake/tuklib_cpucores.cmake)
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include(cmake/tuklib_physmem.cmake)
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@ -402,14 +404,16 @@ check_c_source_compiles("
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cmake_pop_check_state()
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tuklib_add_definition_if(liblzma HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR)
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# cpuid.h
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check_include_file(cpuid.h HAVE_CPUID_H)
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tuklib_add_definition_if(liblzma HAVE_CPUID_H)
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# immintrin.h:
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include(CheckIncludeFile)
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check_include_file(immintrin.h HAVE_IMMINTRIN_H)
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if(HAVE_IMMINTRIN_H)
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target_compile_definitions(liblzma PRIVATE HAVE_IMMINTRIN_H)
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# SSE2 intrinsics:
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include(CheckCSourceCompiles)
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check_c_source_compiles("
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#include <immintrin.h>
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int main(void)
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@ -421,6 +425,24 @@ if(HAVE_IMMINTRIN_H)
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"
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HAVE__MM_MOVEMASK_EPI8)
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tuklib_add_definition_if(liblzma HAVE__MM_MOVEMASK_EPI8)
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# CLMUL intrinsic:
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check_c_source_compiles("
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#include <immintrin.h>
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#if defined(__e2k__) && __iset__ < 6
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# error
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#endif
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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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__m128i my_clmul(__m128i a, __m128i b)
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{
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return _mm_clmulepi64_si128(a, b, 0);
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}
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int main(void) { return 0; }
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"
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HAVE_USABLE_CLMUL)
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tuklib_add_definition_if(liblzma HAVE_USABLE_CLMUL)
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endif()
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# Support -fvisiblity=hidden when building shared liblzma.
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12
INSTALL
12
INSTALL
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@ -370,6 +370,18 @@ XZ Utils Installation
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pre-i686 systems, you may want to disable the assembler
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code.
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--disable-clmul-crc
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Disable the use carryless multiplication for CRC
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calculation even if compiler support for it is detected.
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The code uses runtime detection of SSSE3, SSE4.1, and
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CLMUL instructions on x86. On 32-bit x86 this currently
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is used only if --disable-assembler is used (this might
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be fixed in the future). The code works on E2K too.
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If using compiler options that unconditionally allow the
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required extensions (-msse4.1 -mpclmul) then runtime
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detection isn't used and the generic code is omitted.
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--enable-unaligned-access
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Allow liblzma to use unaligned memory access for 16-bit,
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32-bit, and 64-bit loads and stores. This should be
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59
configure.ac
59
configure.ac
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@ -370,6 +370,16 @@ esac
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AM_CONDITIONAL(COND_ASM_X86, test "x$enable_assembler" = xx86)
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#############
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# CLMUL CRC #
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#############
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AC_ARG_ENABLE([clmul-crc], AS_HELP_STRING([--disable-clmul-crc],
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[Do not use carryless multiplication for CRC calculation
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even if support for it is detected.]),
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[], [enable_clmul_crc=yes])
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#####################
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# Size optimization #
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#####################
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@ -733,8 +743,9 @@ AC_CHECK_HEADERS([fcntl.h limits.h sys/time.h],
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[],
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[AC_MSG_ERROR([Required header file(s) are missing.])])
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# This allows the use of the intrinsic functions if they are available.
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AC_CHECK_HEADERS([immintrin.h])
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# immintrin.h allows the use of the intrinsic functions if they are available.
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# cpuid.h may be used for detecting x86 processor features at runtime.
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AC_CHECK_HEADERS([immintrin.h cpuid.h])
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###############################################################################
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@ -874,6 +885,50 @@ AC_CHECK_DECL([_mm_movemask_epi8],
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#include <immintrin.h>
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#endif])
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# For faster CRC on 32/64-bit x86 and E2K (see also crc64_fast.c):
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#
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# - Check for the CLMUL intrinsic _mm_clmulepi64_si128 in <immintrin.h>.
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#
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# - Check that __attribute__((__target__("ssse3,sse4.1,pclmul"))) works
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# together with _mm_clmulepi64_si128 from <immintrin.h>. The attribute
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# was added in GCC 4.4 but some GCC 4.x versions don't allow intrinsics
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# with it. Exception: it must be not be used with EDG-based compilers
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# like ICC and the compiler on E2K.
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#
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# If everything above is supported, runtime detection will be used to keep the
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# binaries working on systems that don't support the required extensions.
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AC_MSG_CHECKING([if _mm_clmulepi64_si128 is usable])
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if test "x$enable_clmul_crc" = xno ; then
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AC_MSG_RESULT([no, --disable-clmul-crc was used])
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else
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
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#include <immintrin.h>
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// CLMUL works on older E2K instruction set but it is slow due to emulation.
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#if defined(__e2k__) && __iset__ < 6
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# error
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#endif
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// Intel's old compiler (ICC) can define __GNUC__ but the attribute must not
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// be used with it. The new Clang-based ICX needs the attribute.
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// Checking for !defined(__EDG__) catches ICC and other EDG-based compilers.
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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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__m128i my_clmul(__m128i a, __m128i b)
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{
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return _mm_clmulepi64_si128(a, b, 0);
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}
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]])], [
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AC_DEFINE([HAVE_USABLE_CLMUL], [1],
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[Define to 1 if _mm_clmulepi64_si128 is usable.
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See configure.ac for details.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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])
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fi
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# Check for sandbox support. If one is found, set enable_sandbox=found.
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case $enable_sandbox in
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auto | capsicum)
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@ -3,11 +3,25 @@
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/// \file crc64.c
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/// \brief CRC64 calculation
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///
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/// Calculate the CRC64 using the slice-by-four algorithm. This is the same
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/// idea that is used in crc32_fast.c, but for CRC64 we use only four tables
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/// There are two methods in this file. crc64_generic uses the
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/// the slice-by-four algorithm. This is the same idea that is
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/// used in crc32_fast.c, but for CRC64 we use only four tables
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/// instead of eight to avoid increasing CPU cache usage.
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///
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/// crc64_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.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
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/// and the public domain code from https://github.com/rawrunprotected/crc
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/// (URLs were checked on 2022-11-07).
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///
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/// FIXME: Builds for 32-bit x86 use crc64_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 crc64_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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//
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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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@ -15,6 +29,54 @@
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///////////////////////////////////////////////////////////////////////////////
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#include "check.h"
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#undef CRC_GENERIC
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#undef CRC_CLMUL
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#undef CRC_USE_GENERIC_FOR_SMALL_INPUTS
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// If CLMUL cannot be used then only the generic slice-by-four is built.
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#if !defined(HAVE_USABLE_CLMUL)
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# define CRC_GENERIC 1
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// If CLMUL is allowed unconditionally in the compiler options then the
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// generic version can be omitted. Note that this doesn't work with MSVC
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// as I don't know how to detect the features here.
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//
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// NOTE: Keep this this in sync with crc64_table.c.
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#elif (defined(__SSSE3__) && defined(__SSE4_1__) && defined(__PCLMUL__)) \
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|| (defined(__e2k__) && __iset__ >= 6)
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# define CRC_CLMUL 1
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// Otherwise build both and detect at runtime which version to use.
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#else
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# define CRC_GENERIC 1
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# define CRC_CLMUL 1
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/*
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// The generic code is much faster with 1-8-byte inputs and has
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// similar performance up to 16 bytes at least in microbenchmarks
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// (it depends on input buffer alignment too). If both versions are
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// built, this #define will use the generic version for inputs up to
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// 16 bytes and CLMUL for bigger inputs. It saves a little in code
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// size since the special cases for 0-16-byte inputs will be omitted
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// from the CLMUL code.
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# define CRC_USE_GENERIC_FOR_SMALL_INPUTS 1
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*/
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# if defined(_MSC_VER)
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# include <intrin.h>
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# elif defined(HAVE_CPUID_H)
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# include <cpuid.h>
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# endif
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#endif
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/////////////////////////////////
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// Generic slice-by-four CRC64 //
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/////////////////////////////////
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#ifdef CRC_GENERIC
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#include "crc_macros.h"
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@ -26,8 +88,8 @@
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// See the comments in crc32_fast.c. They aren't duplicated here.
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extern LZMA_API(uint64_t)
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lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
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static uint64_t
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crc64_generic(const uint8_t *buf, size_t size, uint64_t crc)
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{
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crc = ~crc;
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@ -71,3 +133,380 @@ lzma_crc64(const uint8_t *buf, size_t size, uint64_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 CRC64 //
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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 crc64_clmul().
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static uint64_t
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calc_lo(uint64_t poly)
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{
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uint64_t a = poly;
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uint64_t b = 0;
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for (unsigned i = 0; i < 64; ++i) {
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b = (b >> 1) | (a << 63);
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a = (a >> 1) ^ (a & 1 ? poly : 0);
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}
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return b;
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}
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static uint64_t
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calc_hi(uint64_t poly, uint64_t a)
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{
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for (unsigned i = 0; i < 64; ++i)
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a = (a >> 1) ^ (a & 1 ? poly : 0);
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return a;
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}
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*/
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#define MASK_L(in, mask, r) \
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r = _mm_shuffle_epi8(in, mask)
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#define MASK_H(in, mask, r) \
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r = _mm_shuffle_epi8(in, _mm_xor_si128(mask, vsign))
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#define MASK_LH(in, mask, low, high) \
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MASK_L(in, mask, low); \
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MASK_H(in, mask, high)
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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 uint64_t
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crc64_clmul(const uint8_t *buf, size_t size, uint64_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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// const uint64_t poly = 0xc96c5795d7870f42; // CRC polynomial
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const uint64_t p = 0x92d8af2baf0e1e85; // (poly << 1) | 1
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const uint64_t mu = 0x9c3e466c172963d5; // (calc_lo(poly) << 1) | 1
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const uint64_t k2 = 0xdabe95afc7875f40; // calc_hi(poly, 1)
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const uint64_t k1 = 0xe05dd497ca393ae4; // calc_hi(poly, k2)
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const __m128i vfold0 = _mm_set_epi64x(p, mu);
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const __m128i vfold1 = _mm_set_epi64x(k2, k1);
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// Create a vector with 8-bit values 0 to 15. This is used to
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// construct control masks for _mm_blendv_epi8 and _mm_shuffle_epi8.
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const __m128i vramp = _mm_setr_epi32(
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0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c);
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// This is used to inverse the control mask of _mm_shuffle_epi8
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// so that bytes that wouldn't be picked with the original mask
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// will be picked and vice versa.
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const __m128i vsign = _mm_set1_epi8(0x80);
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// Memory addresses A to D and the distances between them:
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//
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// A B C D
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// [skip_start][size][skip_end]
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// [ size2 ]
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//
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// A and D are 16-byte aligned. B and C are 1-byte aligned.
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// skip_start and skip_end are 0-15 bytes. size is at least 1 byte.
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//
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// A = aligned_buf will initially point to this address.
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// B = The address pointed by the caller-supplied buf.
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// C = buf + size == aligned_buf + size2
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// D = buf + size + skip_end == aligned_buf + size2 + skip_end
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const size_t skip_start = (size_t)((uintptr_t)buf & 15);
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const size_t skip_end = (size_t)(-(uintptr_t)(buf + size) & 15);
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const __m128i *aligned_buf = (const __m128i *)(
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(uintptr_t)buf & ~(uintptr_t)15);
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// If size2 <= 16 then the whole input fits into a single 16-byte
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// vector. If size2 > 16 then at least two 16-byte vectors must
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// be processed. If size2 > 16 && size <= 16 then there is only
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// one 16-byte vector's worth of input but it is unaligned in memory.
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//
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// NOTE: There is no integer overflow here if the arguments are valid.
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// If this overflowed, buf + size would too.
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size_t size2 = skip_start + size;
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// Masks to be used with _mm_blendv_epi8 and _mm_shuffle_epi8:
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// The first skip_start or skip_end bytes in the vectors will have
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// the high bit (0x80) set. _mm_blendv_epi8 and _mm_shuffle_epi8
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// will produce zeros for these positions. (Bitwise-xor of these
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// masks with vsign will produce the opposite behavior.)
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const __m128i mask_start
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= _mm_sub_epi8(vramp, _mm_set1_epi8(skip_start));
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const __m128i mask_end = _mm_sub_epi8(vramp, _mm_set1_epi8(skip_end));
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// Get the first 1-16 bytes into data0. If loading less than 16 bytes,
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// the bytes are loaded to the high bits of the vector and the least
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// significant positions are filled with zeros.
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const __m128i data0 = _mm_blendv_epi8(_mm_load_si128(aligned_buf),
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_mm_setzero_si128(), mask_start);
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++aligned_buf;
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#if defined(__i386__) || defined(_M_IX86)
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const __m128i initial_crc = _mm_set_epi64x(0, ~crc);
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#else
|
||||
// GCC and Clang would produce good code with _mm_set_epi64x
|
||||
// but MSVC needs _mm_cvtsi64_si128 on x86-64.
|
||||
const __m128i initial_crc = _mm_cvtsi64_si128(~crc);
|
||||
#endif
|
||||
|
||||
__m128i v0, v1, v2, v3;
|
||||
|
||||
#ifndef CRC_USE_GENERIC_FOR_SMALL_INPUTS
|
||||
if (size <= 16) {
|
||||
// Right-shift initial_crc by 1-16 bytes based on "size"
|
||||
// and store the result in v1 (high bytes) and v0 (low bytes).
|
||||
//
|
||||
// NOTE: The highest 8 bytes of initial_crc are zeros so
|
||||
// v1 will be filled with zeros if size >= 8. The highest 8
|
||||
// bytes of v1 will always become zeros.
|
||||
//
|
||||
// [ v1 ][ v0 ]
|
||||
// [ initial_crc ] size == 1
|
||||
// [ initial_crc ] size == 2
|
||||
// [ initial_crc ] size == 15
|
||||
// [ initial_crc ] size == 16 (all in v0)
|
||||
const __m128i mask_low = _mm_add_epi8(
|
||||
vramp, _mm_set1_epi8(size - 16));
|
||||
MASK_LH(initial_crc, mask_low, v0, v1);
|
||||
|
||||
if (size2 <= 16) {
|
||||
// There are 1-16 bytes of input and it is all
|
||||
// in data0. Copy the input bytes to v3. If there
|
||||
// are fewer than 16 bytes, the low bytes in v3
|
||||
// will be filled with zeros. That is, the input
|
||||
// bytes are stored to the same position as
|
||||
// (part of) initial_crc is in v0.
|
||||
MASK_L(data0, mask_end, v3);
|
||||
} else {
|
||||
// There are 2-16 bytes of input but not all bytes
|
||||
// are in data0.
|
||||
const __m128i data1 = _mm_load_si128(aligned_buf);
|
||||
|
||||
// Collect the 2-16 input bytes from data0 and data1
|
||||
// to v2 and v3, and bitwise-xor them with the
|
||||
// low bits of initial_crc in v0. Note that the
|
||||
// the second xor is below this else-block as it
|
||||
// is shared with the other branch.
|
||||
MASK_H(data0, mask_end, v2);
|
||||
MASK_L(data1, mask_end, v3);
|
||||
v0 = _mm_xor_si128(v0, v2);
|
||||
}
|
||||
|
||||
v0 = _mm_xor_si128(v0, v3);
|
||||
v1 = _mm_alignr_epi8(v1, v0, 8);
|
||||
} else
|
||||
#endif
|
||||
{
|
||||
const __m128i data1 = _mm_load_si128(aligned_buf);
|
||||
MASK_LH(initial_crc, mask_start, v0, v1);
|
||||
v0 = _mm_xor_si128(v0, data0);
|
||||
v1 = _mm_xor_si128(v1, data1);
|
||||
|
||||
#define FOLD \
|
||||
v1 = _mm_xor_si128(v1, _mm_clmulepi64_si128(v0, vfold1, 0x00)); \
|
||||
v0 = _mm_xor_si128(v1, _mm_clmulepi64_si128(v0, vfold1, 0x11));
|
||||
|
||||
while (size2 > 32) {
|
||||
++aligned_buf;
|
||||
size2 -= 16;
|
||||
FOLD
|
||||
v1 = _mm_load_si128(aligned_buf);
|
||||
}
|
||||
|
||||
if (size2 < 32) {
|
||||
MASK_H(v0, mask_end, v2);
|
||||
MASK_L(v0, mask_end, v0);
|
||||
MASK_L(v1, mask_end, v3);
|
||||
v1 = _mm_or_si128(v2, v3);
|
||||
}
|
||||
|
||||
FOLD
|
||||
v1 = _mm_srli_si128(v0, 8);
|
||||
#undef FOLD
|
||||
}
|
||||
|
||||
v1 = _mm_xor_si128(_mm_clmulepi64_si128(v0, vfold1, 0x10), v1);
|
||||
v0 = _mm_clmulepi64_si128(v1, vfold0, 0x00);
|
||||
v2 = _mm_clmulepi64_si128(v0, vfold0, 0x10);
|
||||
v0 = _mm_xor_si128(_mm_xor_si128(v2, _mm_slli_si128(v0, 8)), v1);
|
||||
|
||||
#if defined(__i386__) || defined(_M_IX86)
|
||||
return ~(((uint64_t)(uint32_t)_mm_extract_epi32(v0, 3) << 32) |
|
||||
(uint64_t)(uint32_t)_mm_extract_epi32(v0, 2));
|
||||
#else
|
||||
return ~(uint64_t)_mm_extract_epi64(v0, 1);
|
||||
#endif
|
||||
|
||||
#if TUKLIB_GNUC_REQ(4, 6) || defined(__clang__)
|
||||
# pragma GCC diagnostic pop
|
||||
#endif
|
||||
}
|
||||
#endif
|
||||
|
||||
|
||||
////////////////////////
|
||||
// Detect CPU support //
|
||||
////////////////////////
|
||||
|
||||
#if defined(CRC_GENERIC) && defined(CRC_CLMUL)
|
||||
static inline bool
|
||||
is_clmul_supported(void)
|
||||
{
|
||||
int success = 1;
|
||||
uint32_t r[4]; // eax, ebx, ecx, edx
|
||||
|
||||
#if defined(_MSC_VER)
|
||||
// This needs <intrin.h> with MSVC. ICC has it as a built-in
|
||||
// on all platforms.
|
||||
__cpuid(r, 1);
|
||||
#elif defined(HAVE_CPUID_H)
|
||||
// Compared to just using __asm__ to run CPUID, this also checks
|
||||
// that CPUID is supported and saves and restores ebx as that is
|
||||
// needed with GCC < 5 with position-independent code (PIC).
|
||||
success = __get_cpuid(1, &r[0], &r[1], &r[2], &r[3]);
|
||||
#else
|
||||
// Just a fallback that shouldn't be needed.
|
||||
__asm__("cpuid\n\t"
|
||||
: "=a"(r[0]), "=b"(r[1]), "=c"(r[2]), "=d"(r[3])
|
||||
: "a"(1), "c"(0));
|
||||
#endif
|
||||
|
||||
// Returns true if these are supported:
|
||||
// CLMUL (bit 1 in ecx)
|
||||
// SSSE3 (bit 9 in ecx)
|
||||
// SSE4.1 (bit 19 in ecx)
|
||||
const uint32_t ecx_mask = (1 << 1) | (1 << 9) | (1 << 19);
|
||||
return success && (r[2] & ecx_mask) == ecx_mask;
|
||||
|
||||
// Alternative methods that weren't used:
|
||||
// - ICC's _may_i_use_cpu_feature: the other methods should work too.
|
||||
// - GCC >= 6 / Clang / ICX __builtin_cpu_supports("pclmul")
|
||||
//
|
||||
// CPUID decding is needed with MSVC anyway and older GCC. This keeps
|
||||
// the feature checks in the build system simpler too. The nice thing
|
||||
// about __builtin_cpu_supports would be that it generates very short
|
||||
// code as is it only reads a variable set at startup but a few bytes
|
||||
// doesn't matter here.
|
||||
}
|
||||
|
||||
|
||||
#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
|
||||
# define CRC64_FUNC_INIT
|
||||
# define CRC64_SET_FUNC_ATTR __attribute__((__constructor__))
|
||||
#else
|
||||
# define CRC64_FUNC_INIT = &crc64_dispatch
|
||||
# define CRC64_SET_FUNC_ATTR
|
||||
static uint64_t crc64_dispatch(const uint8_t *buf, size_t size, uint64_t crc);
|
||||
#endif
|
||||
|
||||
|
||||
// Pointer to the the selected CRC64 method.
|
||||
static uint64_t (*crc64_func)(const uint8_t *buf, size_t size, uint64_t crc)
|
||||
CRC64_FUNC_INIT;
|
||||
|
||||
|
||||
CRC64_SET_FUNC_ATTR
|
||||
static void
|
||||
crc64_set_func(void)
|
||||
{
|
||||
crc64_func = is_clmul_supported() ? &crc64_clmul : &crc64_generic;
|
||||
return;
|
||||
}
|
||||
|
||||
|
||||
#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
|
||||
static uint64_t
|
||||
crc64_dispatch(const uint8_t *buf, size_t size, uint64_t crc)
|
||||
{
|
||||
// When __attribute__((__constructor__)) isn't supported, set the
|
||||
// function pointer without any locking. If multiple threads run
|
||||
// the detection code in parallel, they will all end up setting
|
||||
// the pointer to the same value. This avoids the use of
|
||||
// mythread_once() on every call to lzma_crc64() but this likely
|
||||
// isn't strictly standards compliant. Let's change it if it breaks.
|
||||
crc64_set_func();
|
||||
return crc64_func(buf, size, crc);
|
||||
}
|
||||
#endif
|
||||
#endif
|
||||
|
||||
|
||||
extern LZMA_API(uint64_t)
|
||||
lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
|
||||
{
|
||||
#if defined(CRC_GENERIC) && defined(CRC_CLMUL)
|
||||
// If CLMUL is available, it is the best for non-tiny inputs,
|
||||
// being over twice as fast as the generic slice-by-four version.
|
||||
// However, for size <= 16 it's different. In the extreme case
|
||||
// of size == 1 the generic version can be five times faster.
|
||||
// At size >= 8 the CLMUL starts to become reasonable. It
|
||||
// varies depending on the alignment of buf too.
|
||||
//
|
||||
// The above doesn't include the overhead of mythread_once().
|
||||
// At least on x86-64 GNU/Linux, pthread_once() is very fast but
|
||||
// it still makes lzma_crc64(buf, 1, crc) 50-100 % slower. When
|
||||
// size reaches 12-16 bytes the overhead becomes negligible.
|
||||
//
|
||||
// So using the generic version for size <= 16 may give better
|
||||
// performance with tiny inputs but if such inputs happen rarely
|
||||
// it's not so obvious because then the lookup table of the
|
||||
// generic version may not be in the processor cache.
|
||||
#ifdef CRC_USE_GENERIC_FOR_SMALL_INPUTS
|
||||
if (size <= 16)
|
||||
return crc64_generic(buf, size, crc);
|
||||
#endif
|
||||
|
||||
/*
|
||||
#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
|
||||
// See crc64_dispatch(). This would be the alternative which uses
|
||||
// locking and doesn't use crc64_dispatch(). Note that on Windows
|
||||
// this method needs Vista threads.
|
||||
mythread_once(crc64_set_func);
|
||||
#endif
|
||||
*/
|
||||
|
||||
return crc64_func(buf, size, crc);
|
||||
|
||||
#elif defined(CRC_CLMUL)
|
||||
// If CLMUL is used unconditionally without runtime CPU detection
|
||||
// then omitting the generic version and its 8 KiB lookup table
|
||||
// makes the library smaller.
|
||||
//
|
||||
// FIXME: Lookup table isn't currently omitted on 32-bit x86,
|
||||
// see crc64_table.c.
|
||||
return crc64_clmul(buf, size, crc);
|
||||
|
||||
#else
|
||||
return crc64_generic(buf, size, crc);
|
||||
#endif
|
||||
}
|
||||
|
|
|
|||
|
|
@ -12,11 +12,24 @@
|
|||
|
||||
#include "common.h"
|
||||
|
||||
|
||||
// FIXME: Compared to crc64_fast.c this has to check for __x86_64__ too
|
||||
// so that in 32-bit builds crc64_x86.S won't break due to a missing table.
|
||||
#if (defined(__x86_64__) && defined(__SSSE3__) \
|
||||
&& defined(__SSE4_1__) && defined(__PCLMUL__)) \
|
||||
|| (defined(__e2k__) && __iset__ >= 6)
|
||||
// No table needed but something has to be exported to keep some toolchains
|
||||
// happy. Also use a declaration to silence compiler warnings.
|
||||
extern const char lzma_crc64_dummy;
|
||||
const char lzma_crc64_dummy;
|
||||
|
||||
#else
|
||||
// Having the declaration here silences clang -Wmissing-variable-declarations.
|
||||
extern const uint64_t lzma_crc64_table[4][256];
|
||||
|
||||
#ifdef WORDS_BIGENDIAN
|
||||
# include "crc64_table_be.h"
|
||||
#else
|
||||
# include "crc64_table_le.h"
|
||||
# if defined(WORDS_BIGENDIAN)
|
||||
# include "crc64_table_be.h"
|
||||
# else
|
||||
# include "crc64_table_le.h"
|
||||
# endif
|
||||
#endif
|
||||
|
|
|
|||
Loading…
Reference in New Issue