| Message ID | 000401cfbc74$758a9b80$609fd280$@com |
|---|---|
| State | New |
| Headers | show |
On 20-08-2014 09:44, Wilco Dijkstra wrote: > Hi, > > This patch improves strncpy performance by using memset to clear memory after the string when the > buffer is much larger than the copied string. This is better as memset is significantly faster than > a simple byte-loop. On bench-strncpy it is ~25% faster. Hi, the patch looks ok. I also pushed a similar modification for powerpc based on same idea. > > ChangeLog: > 2014-08-20 Wilco Dijkstra <wdijkstr@arm.com> > > * string/strncpy.c (strncpy): Improve performance by using memset. > --- > string/strncpy.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/string/strncpy.c b/string/strncpy.c > index 0915e03..604417c 100644 > --- a/string/strncpy.c > +++ b/string/strncpy.c > @@ -78,9 +78,12 @@ STRNCPY (char *s1, const char *s2, size_t n) > while (c != '\0'); > > zero_fill: > - do > - *++s1 = '\0'; > - while (--n > 0); > + if (n >= 8) > + memset (s1 + 1, '\0', n); > + else > + do > + *++s1 = '\0'; > + while (--n > 0); I wonder if this test is really worth, my opinion is just to keep it simple and just call memset on both 'goto' in loop and after 'last_chars'. > > return s; > } > -- 1.7.9.5
diff --git a/string/strncpy.c b/string/strncpy.c index 0915e03..604417c 100644 --- a/string/strncpy.c +++ b/string/strncpy.c @@ -78,9 +78,12 @@ STRNCPY (char *s1, const char *s2, size_t n) while (c != '\0'); zero_fill: - do - *++s1 = '\0'; - while (--n > 0); + if (n >= 8) + memset (s1 + 1, '\0', n); + else + do + *++s1 = '\0'; + while (--n > 0); return s; }