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Improve strcoll with strdiff.

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This patch improves strcoll hot case by finding first byte that
mismatches. That is in likely case enough to determine comparison
result.
This commit is contained in:
Leonhard Holz
2015-05-12 11:37:52 +02:00
committed by Ondřej Bílka
parent 34cb304e5a
commit f13c2a8dff
8 changed files with 71 additions and 2 deletions
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38
string/strcoll_l.c
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@ -29,6 +29,7 @@
# define STRING_TYPE char
# define USTRING_TYPE unsigned char
# define STRCOLL __strcoll_l
# define STRDIFF __strdiff
# define STRCMP strcmp
# define WEIGHT_H "../locale/weight.h"
# define SUFFIX MB
@ -41,6 +42,20 @@
#include "../locale/localeinfo.h"
#include WEIGHT_H
#define MASK_UTF8_7BIT (1 << 7)
#define MASK_UTF8_START (3 << 6)
size_t
STRDIFF (const STRING_TYPE *s, const STRING_TYPE *t)
{
size_t n;
for (n = 0; *s != '\0' && *s++ == *t++; ++n)
continue;
return n;
}
/* Track status while looking for sequences in a string. */
typedef struct
{
@ -255,9 +270,29 @@ STRCOLL (const STRING_TYPE *s1, const STRING_TYPE *s2, __locale_t l)
const USTRING_TYPE *extra;
const int32_t *indirect;
/* In case there is no locale specific sort order (C / POSIX). */
if (nrules == 0)
return STRCMP (s1, s2);
/* Fast forward to the position of the first difference. Needs to be
encoding aware as the byte-by-byte comparison can stop in the middle
of a char sequence for multibyte encodings like UTF-8. */
uint_fast32_t encoding =
current->values[_NL_ITEM_INDEX (_NL_COLLATE_ENCODING_TYPE)].word;
if (encoding != __cet_other)
{
size_t diff = STRDIFF (s1, s2);
if (diff > 0)
{
if (encoding == __cet_utf8 && (*(s1 + diff) & MASK_UTF8_7BIT) != 0)
do
diff--;
while (diff > 0 && (*(s1 + diff) & MASK_UTF8_START) != MASK_UTF8_START);
s1 += diff;
s2 += diff;
}
}
/* Catch empty strings. */
if (__glibc_unlikely (*s1 == '\0') || __glibc_unlikely (*s2 == '\0'))
return (*s1 != '\0') - (*s2 != '\0');
@ -321,7 +356,8 @@ STRCOLL (const STRING_TYPE *s1, const STRING_TYPE *s2, __locale_t l)
byte-level comparison to ensure that we don't waste time
going through multiple passes for totally equal strings
before proceeding to subsequent passes. */
if (pass == 0 && STRCMP (s1, s2) == 0)
if (pass == 0 && encoding == __cet_other &&
STRCMP (s1, s2) == 0)
return result;
else
break;