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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 15:48:19 +0100 |
| commit | ecd6271ed80e71b3b1f286e2977f534d54c33af4 (patch) | |
| tree | efc16baedc0d5d33d9792b0b1702521de9a854c6 | |
| parent | bba6b9288f5192b67947e478ef9033920d22216a (diff) | |
| download | glibc-ecd6271ed80e71b3b1f286e2977f534d54c33af4.tar.gz glibc-ecd6271ed80e71b3b1f286e2977f534d54c33af4.tar.xz glibc-ecd6271ed80e71b3b1f286e2977f534d54c33af4.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
diff --git a/ChangeLog b/ChangeLog index 00e666b02d..d4bd101fb4 100644 --- a/ChangeLog +++ b/ChangeLog @@ -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 |