root
/
xz
mirror of https://git.tukaani.org/xz.git
1
0
Fork 0
Code Issues Releases Wiki Activity
xz/src/liblzma/check/crc64_table.c

34 lines
1.0 KiB
C
Raw Normal View History

Imported to git.
2007-12-08 22:42:33 +00:00
///////////////////////////////////////////////////////////////////////////////
//
/// \file crc64_table.c
/// \brief Precalculated CRC64 table with correct endianness
//
Put the interesting parts of XZ Utils into the public domain. Some minor documentation cleanups were made at the same time.
2009-04-13 08:27:40 +00:00
// Author: Lasse Collin
Imported to git.
2007-12-08 22:42:33 +00:00
//
Put the interesting parts of XZ Utils into the public domain. Some minor documentation cleanups were made at the same time.
2009-04-13 08:27:40 +00:00
// This file has been put into the public domain.
// You can do whatever you want with this file.
Imported to git.
2007-12-08 22:42:33 +00:00
//
///////////////////////////////////////////////////////////////////////////////
Removed src/liblzma/common/sysdefs.h symlink, which was annoying, because "make dist" put two copies of sysdefs.h into the tarball instead of the symlink.
2008-04-25 10:58:56 +00:00
#include "common.h"
Imported to git.
2007-12-08 22:42:33 +00:00
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
2022-11-14 19:34:57 +00:00
// 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)
liblzma: Update a comment. The C standards don't allow an empty translation unit which can be avoided by declaring something, without exporting any symbols. When I committed f644473a211394447824ea00518d0a214ff3f7f2 I had a feeling that some specific toolchain somewhere didn't like empty object files (assembler or maybe "ar" complained) but I cannot find anything to confirm this now. Quite likely I remembered nonsense. I leave this here as a note to my future self. :-)
2023-09-26 18:47:13 +00:00
// No table needed. Use a typedef to avoid an empty translation unit.
liblzma: Avoid compiler warning without creating extra symbol. When the generic fast crc64 method is used, then we omit lzma_crc64_table[][]. Similar to d9166b52cf3458a4da3eb92224837ca8fc208d79, we can avoid compiler warnings with -Wempty-translation-unit (Clang) or -pedantic (GCC) by creating a never used typedef instead of an extra symbol.
2023-09-26 16:02:11 +00:00
typedef void lzma_crc64_dummy;
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
2022-11-14 19:34:57 +00:00
#else
liblzma: Silence clang -Wmissing-variable-declarations.
2019-06-24 20:45:21 +00:00
// Having the declaration here silences clang -Wmissing-variable-declarations.
extern const uint64_t lzma_crc64_table[4][256];
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
2022-11-14 19:34:57 +00:00
# if defined(WORDS_BIGENDIAN)
# include "crc64_table_be.h"
# else
# include "crc64_table_le.h"
# endif
Imported to git.
2007-12-08 22:42:33 +00:00
#endif