diff mbox series

[2/3] lib/string: optimized memmove

Message ID 20210625010200.362755-3-mcroce@linux.microsoft.com (mailing list archive)
State New, archived
Headers show
Series lib/string: optimized mem* functions | expand

Commit Message

Matteo Croce June 25, 2021, 1:01 a.m. UTC 
From: Matteo Croce <mcroce@microsoft.com>

When the destination buffer is before the source one, or when the
buffers doesn't overlap, it's safe to use memcpy() instead, which is
optimized to use a bigger data size possible.

This "optimization" only covers a common case. In future, proper code
which does the same thing as memcpy() does but backwards can be done.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
---
 lib/string.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)
diff mbox series

Patch

diff --git a/lib/string.c b/lib/string.c
index 15e906f97d9e..69adec252597 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -976,19 +976,13 @@  EXPORT_SYMBOL(memcpy);
  */
 void *memmove(void *dest, const void *src, size_t count)
 {
-	char *tmp;
-	const char *s;
+	if (dest < src || src + count <= dest)
+		return memcpy(dest, src, count);
+
+	if (dest > src) {
+		const char *s = src + count;
+		char *tmp = dest + count;
 
-	if (dest <= src) {
-		tmp = dest;
-		s = src;
-		while (count--)
-			*tmp++ = *s++;
-	} else {
-		tmp = dest;
-		tmp += count;
-		s = src;
-		s += count;
 		while (count--)
 			*--tmp = *--s;
 	}