From ceeba1d73c84f1a551677149ce3b3ed3372fb3ec Mon Sep 17 00:00:00 2001 From: Rajalakshmi Srinivasaraghavan Date: Tue, 28 Aug 2018 12:42:19 +0530 Subject: [PATCH] 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) --- ChangeLog | 4 ++++ string/memmem.c | 4 ++++ 2 files changed, 8 insertions(+) diff --git a/ChangeLog b/ChangeLog index 22012fb458..12e7d27e49 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,7 @@ +2019-09-13 Rajalakshmi Srinivasaraghavan + + * string/memmem.c: Use memcmp for first match. + 2019-09-13 Wilco Dijkstra * string/strcasestr.c (STRCASESTR): Simplify and speedup first match. diff --git a/string/memmem.c b/string/memmem.c index 34299b8864..645b6d1a26 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