[U-Boot] [PATCH] uboot optimize memmove

[Andy Green]

While studying the reason why kernel copy from NOR was so slow on our platform,
I realized U-Boot is pulling it from 32-bit NOR in 8-bit chunks needlessly.

bootm uses memmove() and that just takes the approach by default to move u8s
around.

This optimization prefers memcpy() implementation (done mostly in 32-bit reads
and writes) if there's no overlap in source and dest, resulting in a huge
speedup on our platform (480ms copy from 32-bit NOR ---> 140ms)

Signed-off-by: Andy Green <andy.green at linaro.org>
---
 lib/string.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/string.c b/lib/string.c
index c3ad055..96d66e0 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -542,13 +542,21 @@ void * memmove(void * dest,const void *src,size_t count)
 	if (src == dest)
 		return dest;
 
-	if (dest <= src) {
+	if (dest < src) {
+
+		if ((unsigned long)dest + count <= (unsigned long)src)
+			return memcpy(dest, src, count);
+
 		tmp = (char *) dest;
 		s = (char *) src;
 		while (count--)
 			*tmp++ = *s++;
 		}
 	else {
+
+		if ((unsigned long)src + count <= (unsigned long)dest)
+			return memcpy(dest, src, count);
+
 		tmp = (char *) dest + count;
 		s = (char *) src + count;
 		while (count--)