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Improve memccpy performance

Message ID 000701d052a0$79ec7910$6dc56b30$@com
State New
Headers show

Commit Message

Wilco Feb. 27, 2015, 3:17 p.m. UTC 
> Wilco Dijkstra wrote:
> > Richard Earnshaw wrote:
> > On 14/01/15 18:14, Roland McGrath wrote:
> > >> +      return memcpy (dest, src, n) + n;
> > >
> > > Use __mempcpy here.
> > >
> > That will be worse if mempcpy just calls memcpy; which is what the C
> > library implementation does.
> 
> If GLIBC inlines mempcpy like I proposed then it would be reasonable
> to use mempcpy here as it results in exactly the same code.

So, OK for trunk with __mempcpy like below?

---
 string/memccpy.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)
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Patch

diff --git a/string/memccpy.c b/string/memccpy.c
index 70ee2ae..d4146f9 100644
--- a/string/memccpy.c
+++ b/string/memccpy.c
@@ -26,15 +26,15 @@ 
 void *
 __memccpy (void *dest, const void *src, int c, size_t n)
 {
-  const char *s = src;
-  char *d = dest;
-  const char x = c;
-  size_t i = n;
+  void *p = memchr (src, c, n);
 
-  while (i-- > 0)
-    if ((*d++ = *s++) == x)
-      return d;
+  if (p != NULL)
+    {
+      n = p - src + 1;
+      return __mempcpy (dest, src, n);
+    }
 
+  memcpy (dest, src, n);
   return NULL;
 }