[3/3] x86_64/lib: improve the performance of memmove

Commit Message

Miao Xie Sept. 1, 2010, 10:36 a.m. UTC

None

Patch

diff --git a/arch/x86/lib/memmove_64.c b/arch/x86/lib/memmove_64.c
index 0a33909..3640232 100644
--- a/arch/x86/lib/memmove_64.c
+++ b/arch/x86/lib/memmove_64.c
@@ -4,17 +4,17 @@ 
 #define _STRING_C
 #include <linux/string.h>
 #include <linux/module.h>
+#include <linux/memcopy.h>
 
 #undef memmove
 void *memmove(void *dest, const void *src, size_t count)
 {
-	if (dest < src) {
+	if (dest - src >= count) {	/* *Unsigned* compare! */
 		return memcpy(dest, src, count);
 	} else {
-		char *p = dest + count;
-		const char *s = src + count;
-		while (count--)
-			*--p = *--s;
+		unsigned long dstp = (unsigned long)dest;
+		unsigned long srcp = (unsigned long)src;
+		mem_copy_bwd(dstp, srcp, count);
 	}
 	return dest;
 }