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| author | Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com> | 2018-08-28 12:42:19 +0530 |
|---|---|---|
| committer | Wilco Dijkstra <wdijkstr@arm.com> | 2019-09-13 15:17:56 +0100 |
| commit | d6ccf2f45c5e09d3a36321ba695325589e8940fe (patch) | |
| tree | f08fef2fe858f893afb252bf5213146a5d43238c | |
| parent | 1def6a34aee55e26a0755a3e36bf2e184a4cdf5e (diff) | |
| download | glibc-d6ccf2f45c5e09d3a36321ba695325589e8940fe.tar glibc-d6ccf2f45c5e09d3a36321ba695325589e8940fe.tar.gz glibc-d6ccf2f45c5e09d3a36321ba695325589e8940fe.tar.bz2 glibc-d6ccf2f45c5e09d3a36321ba695325589e8940fe.zip | |
Speedup first memmem match
As done in commit 284f42bc778e487dfd5dff5c01959f93b9e0c4f5, 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 c8dd67e7c958de04c3783cbea7c384431707b5f8)
| -rw-r--r-- | ChangeLog | 4 | ||||
| -rw-r--r-- | string/memmem.c | 4 |
2 files changed, 8 insertions, 0 deletions
@@ -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. diff --git a/string/memmem.c b/string/memmem.c index 43efaa3fb7..d72b8249e6 100644 --- a/string/memmem.c +++ b/string/memmem.c @@ -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 |