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680942b016
glibc/string
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Wilco Dijkstra 680942b016 Improve performance of memmem 
This patch significantly improves performance of memmem using a novel
modified Horspool algorithm.  Needles up to size 256 use a bad-character
table indexed by hashed pairs of characters to quickly skip past mismatches.
Long needles use a self-adapting filtering step to avoid comparing the whole
needle repeatedly.

By limiting the needle length to 256, the shift table only requires 8 bits
per entry, lowering preprocessing overhead and minimizing cache effects.
This limit also implies worst-case performance is linear.

Small needles up to size 2 use a dedicated linear search.  Very long needles
use the Two-Way algorithm (to avoid increasing stack size or slowing down
the common case, inlining is disabled).

The performance gain is 6.6 times on English text on AArch64 using random
needles with average size 8.

Tested against GLIBC testsuite and randomized tests.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

	* string/memmem.c (__memmem): Rewrite to improve performance.
2019-06-12 11:42:34 +01:00
..
bits Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
_strerror.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
argz-addsep.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
argz-append.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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argz-extract.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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argz-replace.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
argz-stringify.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
argz.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
basename.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
bcopy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
bug-envz1.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
bug-strcoll1.c Update. 2001-04-26 20:45:18 +00:00
bug-strcoll2.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
bug-strncat1.c Fix string/bug-strncat1.c build with GCC 8. 2017-11-14 17:50:36 +00:00
bug-strpbrk1.c Fix bug-strspn1.c, bug-strpbrk1.c build with GCC mainline. 2018-06-20 22:18:22 +00:00
bug-strspn1.c Fix bug-strspn1.c, bug-strpbrk1.c build with GCC mainline. 2018-06-20 22:18:22 +00:00
bug-strtok1.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
byteswap.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
bzero.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
Depend Update. 2001-03-19 21:40:15 +00:00
endian.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
envz.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
envz.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
explicit_bzero.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
ffs.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
ffsll.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
inl-tester.c
Makefile Only build libm with -fno-math-errno (bug 24024) 2019-01-07 14:59:07 +01:00
memccpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memcmp.c Add some spaces before '('. 2019-02-27 13:55:45 +00:00
memcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memfrob.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memmem.c Improve performance of memmem 2019-06-12 11:42:34 +01:00
memmove.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memory.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
mempcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memrchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
memset.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
noinl-tester.c
rawmemchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
stpcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
stpncpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
str-two-way.h Improve performance of strstr 2019-06-12 11:38:52 +01:00
stratcliff.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcasecmp_l.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcasecmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcasestr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcat.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strchr.c Break more lines before not after operators. 2019-02-25 13:19:19 +00:00
strchrnul.c Break more lines before not after operators. 2019-02-25 13:19:19 +00:00
strcmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcoll_l.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcoll.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strcspn.c Break some lines before not after operators. 2019-02-22 01:32:36 +00:00
strdup.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strerror_l.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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strfry.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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string.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strings.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strlen.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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strncat.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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strnlen.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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strrchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strsep.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strsignal.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strspn.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strstr.c Improve performance of strstr 2019-06-12 11:38:52 +01:00
strtok_r.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strtok.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strverscmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
strxfrm_l.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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swab.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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test-memccpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memcmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memmem.c Break some lines before not after operators. 2019-02-22 01:32:36 +00:00
test-memmove.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-mempcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memrchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-memset.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-rawmemchr.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-stpcpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-stpncpy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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test-strcmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-strcpy.c Add some spaces before '('. 2019-02-27 13:55:45 +00:00
test-strcspn.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-strerror-errno.c Only build libm with -fno-math-errno (bug 24024) 2019-01-07 14:59:07 +01:00
test-string.h Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-strlen.c Add some spaces before '('. 2019-02-27 13:55:45 +00:00
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test-strncat.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
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test-strpbrk.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
test-strrchr.c Add some spaces before '('. 2019-02-27 13:55:45 +00:00
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testcopy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
tester.c Add some spaces before '('. 2019-02-27 13:55:45 +00:00
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tst-cmp.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
tst-endian.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-inlcall.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
tst-strcoll-overflow.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
tst-strfry.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-strlen.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-strtok_r.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
tst-strtok.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-strxfrm2.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-strxfrm.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-svc2.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-svc.c Update string tests to use the support test driver. 2017-03-23 11:32:29 -03:00
tst-svc.expect * string/strverscmp.c (__strverscmp): Fix last cleanups. 2009-04-07 06:51:59 +00:00
tst-svc.input * string/strverscmp.c (__strverscmp): Fix last cleanups. 2009-04-07 06:51:59 +00:00
tst-xbzero-opt.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
Versions New string function explicit_bzero (from OpenBSD). 2016-12-16 16:21:54 -05:00
wordcopy.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00
xpg-strerror.c Update copyright dates with scripts/update-copyrights. 2019-01-01 00:11:28 +00:00