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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.
This commit is contained in:
Rajalakshmi Srinivasaraghavan
2018-08-28 12:42:19 +05:30
parent 5abedf97a3
commit c8dd67e7c9
2 changed files with 8 additions and 0 deletions
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ChangeLog
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@ -1,3 +1,7 @@
2018-08-28 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
* string/memmem.c: Use memcmp for first match.
2018-08-28 Rafal Luzynski <digitalfreak@lingonborough.com> 2018-08-28 Rafal Luzynski <digitalfreak@lingonborough.com>
[BZ #17426] [BZ #17426]

4
string/memmem.c
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@ -70,6 +70,10 @@ __memmem (const void *haystack_start, size_t haystack_len,
haystack_len -= haystack - (const unsigned char *) haystack_start; haystack_len -= haystack - (const unsigned char *) haystack_start;
if (haystack_len < needle_len) if (haystack_len < needle_len)
return NULL; 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); return two_way_short_needle (haystack, haystack_len, needle, needle_len);
} }
else else