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Speedup first memmem match

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As done in commit 284f42bc77, memcmp
can be used after memchr to avoid the initialization overhead of the
two-way algorithm for the first match.  This has shown improvement
>40% for first match.

(cherry picked from commit c8dd67e7c9)
This commit is contained in:
Rajalakshmi Srinivasaraghavan 2018-08-28 12:42:19 +05:30 committed by Wilco Dijkstra
parent c60bf879b2
commit ceeba1d73c
2 changed files with 8 additions and 0 deletions
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4
ChangeLog
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@ -1,3 +1,7 @@
2019-09-13 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
* string/memmem.c: Use memcmp for first match.
2019-09-13 Wilco Dijkstra <wdijkstr@arm.com>
* string/strcasestr.c (STRCASESTR): Simplify and speedup first match.

4
string/memmem.c
View File

@ -70,6 +70,10 @@ __memmem (const void *haystack_start, size_t haystack_len,
haystack_len -= haystack - (const unsigned char *) haystack_start;
if (haystack_len < needle_len)
return NULL;
/* Check whether we have a match. This improves performance since we
avoid the initialization overhead of the two-way algorithm. */
if (memcmp (haystack, needle, needle_len) == 0)
return (void *) haystack;
return two_way_short_needle (haystack, haystack_len, needle, needle_len);
}
else