GNU C Library master sources branch master updated. glibc-2.28.9000-100-gc8dd67e

[raji at sourceware dot org]

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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c8dd67e7c958de04c3783cbea7c384431707b5f8

commit c8dd67e7c958de04c3783cbea7c384431707b5f8
Author: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
Date:   Tue Aug 28 12:42:19 2018 +0530

    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.

diff --git a/ChangeLog b/ChangeLog
index 8419d46..2a25097 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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>
 
 	[BZ #17426]
diff --git a/string/memmem.c b/string/memmem.c
index 43efaa3..d72b824 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

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog       |    4 ++++
 string/memmem.c |    4 ++++
 2 files changed, 8 insertions(+), 0 deletions(-)


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