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Optimize the generic strchr.

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* libc/string/strchr.c (strchr) [!__OPTIMIZE_SIZE__]: Pre-align
data so unaligned searches aren't penalized.  Special-case
searching for 0.
This commit is contained in:
Eric Blake 2008-05-22 02:31:46 +00:00
parent 0b99028af4
commit ae47b14a12
2 changed files with 54 additions and 33 deletions
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10
newlib/ChangeLog
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@ -1,8 +1,14 @@
2008-05-21 Eric Blake <ebb9@byu.net> 2008-05-21 Eric Blake <ebb9@byu.net>
Optimize the generic strchr.
* libc/string/strchr.c (strchr) [!__OPTIMIZE_SIZE__]: Pre-align
data so unaligned searches aren't penalized. Special-case
searching for 0.
Optimize strchr for x86. Optimize strchr for x86.
* libc/machine/i386/strchr.S (strchr): Pre-align data so unaligned * libc/machine/i386/strchr.S (strchr) [!__OPTIMIZE_SIZE__]:
searches aren't penalized. Special-case searching for 0. Pre-align data so unaligned searches aren't penalized.
Special-case searching for 0.
2008-05-20 Nick Clifton <nickc@redhat.com> 2008-05-20 Nick Clifton <nickc@redhat.com>

57
newlib/libc/string/strchr.c
View File

@ -63,30 +63,45 @@ _DEFUN (strchr, (s1, i),
int i) int i)
{ {
_CONST unsigned char *s = (_CONST unsigned char *)s1; _CONST unsigned char *s = (_CONST unsigned char *)s1;
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) unsigned char c = i;
unsigned char c = (unsigned int)i;
while (*s && *s != c) #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
{
s++;
}
if (*s != c)
{
s = NULL;
}
return (char *) s;
#else
unsigned char c = (unsigned char)i;
unsigned long mask,j; unsigned long mask,j;
unsigned long *aligned_addr; unsigned long *aligned_addr;
if (!UNALIGNED (s)) /* Special case for finding 0. */
if (!c)
{ {
mask = 0; while (UNALIGNED (s))
for (j = 0; j < LBLOCKSIZE; j++) {
mask = (mask << 8) | c; if (!*s)
return (char *) s;
s++;
}
/* Operate a word at a time. */
aligned_addr = (unsigned long *) s;
while (!DETECTNULL (*aligned_addr))
aligned_addr++;
/* Found the end of string. */
s = (const unsigned char *) aligned_addr;
while (*s)
s++;
return (char *) s;
}
/* All other bytes. Align the pointer, then search a long at a time. */
while (UNALIGNED (s))
{
if (!*s)
return NULL;
if (*s == c)
return (char *) s;
s++;
}
mask = c;
for (j = 8; j < LBLOCKSIZE * 8; j <<= 1)
mask = (mask << j) | mask;
aligned_addr = (unsigned long *) s; aligned_addr = (unsigned long *) s;
while (!DETECTNULL (*aligned_addr) && !DETECTCHAR (*aligned_addr, mask)) while (!DETECTNULL (*aligned_addr) && !DETECTCHAR (*aligned_addr, mask))
@ -97,12 +112,12 @@ _DEFUN (strchr, (s1, i),
catch it using the bytewise search. */ catch it using the bytewise search. */
s = (unsigned char *) aligned_addr; s = (unsigned char *) aligned_addr;
}
#endif /* not PREFER_SIZE_OVER_SPEED */
while (*s && *s != c) while (*s && *s != c)
s++; s++;
if (*s == c) if (*s == c)
return (char *)s; return (char *)s;
return NULL; return NULL;
#endif /* not PREFER_SIZE_OVER_SPEED */
} }