This patch cleans up the strsep implementation and improves performance.

Currently strsep calls strpbrk is is now a veneer to strcspn.  Calling
strcspn directly is faster.  Since it handles a delimiter string of size
1 as a special case, this is not needed in strsep itself.  Although this
means there is a slightly higher overhead if the delimiter size is 1,
all other cases are slightly faster.  The overall performance gain is 5-10%
on AArch64.

The string/bits/string2.h header contains optimizations for constant
delimiters of size 1-3.  Benchmarking these showed similar performance for
size 1 (since in all cases strchr/strchrnul is used), while size 2 and 3
can give up to 2x speedup for small input strings.  However if these cases
are common it seems much better to add this optimization to strcspn.
So move these header optimizations to string-inlines.c.

Improve the strsep benchmark so that it actually benchmarks something.
The current version contains a delimiter character at every position in the
input string, so there is very little work to do, and the extremely inefficent
simple_strsep implementation appears fastest in every case.  The new version
has either no match in the input for the fail case and a match halfway in the
input for the success case.  The input is then restored so that each iteration
does exactly the same amount of work.  Reduce the number of testcases since
simple_strsep takes a lot of time now.

	* benchtests/bench-strsep.c (oldstrsep): Add old implementation.
	(do_one_test) Restore original string so iteration works.
	* string/string-inlines.c (do_test): Create better input strings.
	(test_main) Reduce number of testruns.
	* string/string-inlines.c (__old_strsep_1c): New function.
	(__old_strsep_2c): Likewise.
	(__old_strsep_3c): Likewise.
	* string/strsep.c (__strsep): Remove case of small delim string.
	Call strcspn directly rather than strpbrk.
	* string/bits/string2.h (__strsep): Remove define.
	(__strsep_1c): Remove.
	(__strsep_2c): Remove.
	(__strsep_3c): Remove.
	(strsep): Remove.
	* sysdeps/unix/sysv/linux/internal_statvfs.c
	(__statvfs_getflags): Rename to __strsep.

1 files changed, 58 insertions, 21 deletions

diff --git a/benchtests/bench-strsep.c b/benchtests/bench-strsep.c
index 774a093..4a53b4f 100644
--- a/benchtests/bench-strsep.c
+++ b/benchtests/bench-strsep.c
@@ -49,10 +49,56 @@ simple_strsep (char **s1, char *s2)
   return begin;
 }
 
+char *
+oldstrsep (char **stringp, const char *delim)
+{
+  char *begin, *end;
+
+  begin = *stringp;
+  if (begin == NULL)
+    return NULL;
+
+  /* A frequent case is when the delimiter string contains only one
+     character.  Here we don't need to call the expensive `strpbrk'
+     function and instead work using `strchr'.  */
+  if (delim[0] == '\0' || delim[1] == '\0')
+    {
+      char ch = delim[0];
+
+      if (ch == '\0')
+	end = NULL;
+      else
+	{
+	  if (*begin == ch)
+	    end = begin;
+	  else if (*begin == '\0')
+	    end = NULL;
+	  else
+	    end = strchr (begin + 1, ch);
+	}
+    }
+  else
+    /* Find the end of the token.  */
+    end = strpbrk (begin, delim);
+
+  if (end)
+    {
+      /* Terminate the token and set *STRINGP past NUL character.  */
+      *end++ = '\0';
+      *stringp = end;
+    }
+  else
+    /* No more delimiters; this is the last token.  */
+    *stringp = NULL;
+
+  return begin;
+}
+
 typedef char *(*proto_t) (const char **, const char *);
 
 IMPL (simple_strsep, 0)
 IMPL (strsep, 1)
+IMPL (oldstrsep, 2)
 
 static void
 do_one_test (impl_t * impl, const char *s1, const char *s2)
@@ -63,7 +109,10 @@ do_one_test (impl_t * impl, const char *s1, const char *s2)
   TIMING_NOW (start);
   for (i = 0; i < iters; ++i)
     {
-      CALL (impl, &s1, s2);
+      const char *s1a = s1;
+      CALL (impl, &s1a, s2);
+      if (s1a != NULL)
+	((char*)s1a)[-1] = '1';
     }
   TIMING_NOW (stop);
 
@@ -76,7 +125,10 @@ static void
 do_test (size_t align1, size_t align2, size_t len1, size_t len2, int fail)
 {
   char *s2 = (char *) (buf2 + align2);
-  static const char d[] = "1234567890abcdef";
+
+  /* Search for a delimiter in a string containing mostly '0', so don't
+     use '0' as a delimiter.  */
+  static const char d[] = "123456789abcdefg";
 #define dl (sizeof (d) - 1)
   char *ss2 = s2;
   for (size_t l = len2; l > 0; l = l > dl ? l - dl : 0)
@@ -92,24 +144,9 @@ do_test (size_t align1, size_t align2, size_t len1, size_t len2, int fail)
   FOR_EACH_IMPL (impl, 0)
   {
     char *s1 = (char *) (buf1 + align1);
-    if (fail)
-      {
-	char *ss1 = s1;
-	for (size_t l = len1; l > 0; l = l > dl ? l - dl : 0)
-	  {
-	    size_t t = l > dl ? dl : l;
-	    memcpy (ss1, d, t);
-	    ++ss1[len2 > 7 ? 7 : len2 - 1];
-	    ss1 += t;
-	  }
-      }
-    else
-      {
-	memset (s1, '0', len1);
-	memcpy (s1 + (len1 - len2) - 2, s2, len2);
-	if ((len1 / len2) > 4)
-	  memcpy (s1 + (len1 - len2) - (3 * len2), s2, len2);
-      }
+    memset (s1, '0', len1);
+    if (!fail)
+      s1[len1 / 2] = '1';
     s1[len1] = '\0';
     do_one_test (impl, s1, s2);
   }
@@ -127,7 +164,7 @@ test_main (void)
   putchar ('\n');
 
   for (size_t klen = 2; klen < 32; ++klen)
-    for (size_t hlen = 2 * klen; hlen < 16 * klen; hlen += klen)
+    for (size_t hlen = 4 * klen; hlen < 8 * klen; hlen += klen)
       {
 	do_test (0, 0, hlen, klen, 0);
 	do_test (0, 0, hlen, klen, 1);