2013-12-14 18:33:56 +00:00
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/* Multiple versions of strstr.
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All versions must be listed in ifunc-impl-list.c.
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2024-01-01 18:12:26 +00:00
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Copyright (C) 2012-2024 Free Software Foundation, Inc.
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2009-07-21 04:06:50 +00:00
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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2012-02-09 23:18:22 +00:00
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License along with the GNU C Library; if not, see
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Prefer https to http for gnu.org and fsf.org URLs
Also, change sources.redhat.com to sourceware.org.
This patch was automatically generated by running the following shell
script, which uses GNU sed, and which avoids modifying files imported
from upstream:
sed -ri '
s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g
s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g
' \
$(find $(git ls-files) -prune -type f \
! -name '*.po' \
! -name 'ChangeLog*' \
! -path COPYING ! -path COPYING.LIB \
! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \
! -path manual/texinfo.tex ! -path scripts/config.guess \
! -path scripts/config.sub ! -path scripts/install-sh \
! -path scripts/mkinstalldirs ! -path scripts/move-if-change \
! -path INSTALL ! -path locale/programs/charmap-kw.h \
! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \
! '(' -name configure \
-execdir test -f configure.ac -o -f configure.in ';' ')' \
! '(' -name preconfigure \
-execdir test -f preconfigure.ac ';' ')' \
-print)
and then by running 'make dist-prepare' to regenerate files built
from the altered files, and then executing the following to cleanup:
chmod a+x sysdeps/unix/sysv/linux/riscv/configure
# Omit irrelevant whitespace and comment-only changes,
# perhaps from a slightly-different Autoconf version.
git checkout -f \
sysdeps/csky/configure \
sysdeps/hppa/configure \
sysdeps/riscv/configure \
sysdeps/unix/sysv/linux/csky/configure
# Omit changes that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines
git checkout -f \
sysdeps/powerpc/powerpc64/ppc-mcount.S \
sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
# Omit change that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline
git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
2019-09-07 05:40:42 +00:00
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<https://www.gnu.org/licenses/>. */
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2009-07-21 04:06:50 +00:00
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2013-12-14 18:33:56 +00:00
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/* Redefine strstr so that the compiler won't complain about the type
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mismatch with the IFUNC selector in strong_alias, below. */
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#undef strstr
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#define strstr __redirect_strstr
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#include <string.h>
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#undef strstr
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2022-06-24 16:42:13 +00:00
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#define STRSTR __strstr_generic
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2013-12-14 18:33:56 +00:00
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#ifdef SHARED
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# undef libc_hidden_builtin_def
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# define libc_hidden_builtin_def(name) \
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2022-06-24 16:42:13 +00:00
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__hidden_ver1 (__strstr_generic, __GI_strstr, __strstr_generic);
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2009-07-21 04:06:50 +00:00
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#endif
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2013-12-14 18:33:56 +00:00
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#include "string/strstr.c"
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2009-07-21 04:06:50 +00:00
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2013-12-14 18:33:56 +00:00
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extern __typeof (__redirect_strstr) __strstr_sse2_unaligned attribute_hidden;
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2022-06-24 16:42:13 +00:00
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extern __typeof (__redirect_strstr) __strstr_generic attribute_hidden;
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2009-07-21 04:06:50 +00:00
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2013-12-14 18:33:56 +00:00
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#include "init-arch.h"
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2009-07-21 14:52:12 +00:00
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2013-12-14 18:33:56 +00:00
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/* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
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ifunc symbol properly. */
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extern __typeof (__redirect_strstr) __libc_strstr;
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x86_64: Remove avx512 strstr implementation
As indicated in a recent thread, this it is a simple brute-force
algorithm that checks the whole needle at a matching character pair
(and does so 1 byte at a time after the first 64 bytes of a needle).
Also it never skips ahead and thus can match at every haystack
position after trying to match all of the needle, which generic
implementation avoids.
As indicated by Wilco, a 4x larger needle and 16x larger haystack gives
a clear 65x slowdown both basic_strstr and __strstr_avx512:
"ifuncs": ["basic_strstr", "twoway_strstr", "__strstr_avx512",
"__strstr_sse2_unaligned", "__strstr_generic"],
{
"len_haystack": 65536,
"len_needle": 1024,
"align_haystack": 0,
"align_needle": 0,
"fail": 1,
"desc": "Difficult bruteforce needle",
"timings": [4.0948e+07, 15094.5, 3.20818e+07, 108558, 10839.2]
},
{
"len_haystack": 1048576,
"len_needle": 4096,
"align_haystack": 0,
"align_needle": 0,
"fail": 1,
"desc": "Difficult bruteforce needle",
"timings": [2.69767e+09, 100797, 2.08535e+09, 495706, 82666.9]
}
PS: I don't have an AVX512 capable machine to verify this issues, but
skimming through the code it does seems to follow what Wilco has
described.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
2024-03-21 17:12:00 +00:00
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libc_ifunc (__libc_strstr,
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HAS_ARCH_FEATURE (Fast_Unaligned_Load)
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? __strstr_sse2_unaligned
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: __strstr_generic)
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2013-12-14 18:33:56 +00:00
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#undef strstr
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strong_alias (__libc_strstr, strstr)
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