A common use of memmove() can be handled by memcpy(). Also memcpy() includes an optimization for large sizes: it copies a word at a time. So we can get a speed-up by calling memcpy() to handle our move in this case.
Update memmove() to call also memcpy() if the source don't overlap the destination (src + count <= dest).
Signed-off-by: Patrick Delaunay patrick.delaunay@foss.st.com --- Hi,
V2 of http://patchwork.ozlabs.org/project/uboot/list/?series=216620
This patch allows to save 38ms for Kernel Image extraction (7327624 Bytes) from FIT loaded at 0xC2000000 for ARMV7 board STM32MP157C-EV1, and with kernel destination = Load Address: 0xc4000000, located after the FIT without overlap, compared with destination = Load Address: 0xc0008000.
-> 14,332 us vs 52,239 in bootstage report
In this case the memmove funtion is called in common/image.c::memmove_wd() to handle overlap.
Patrick
Changes in v2: - Add a comment on potential issue if the memcpy is not doing a forward-copying
lib/string.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/lib/string.c b/lib/string.c index ae7835f600..73b984123d 100644 --- a/lib/string.c +++ b/lib/string.c @@ -567,7 +567,19 @@ void * memmove(void * dest,const void *src,size_t count) { char *tmp, *s;
- if (dest <= src) { + if (dest <= src || (src + count) <= dest) { + /* + * Use the fast memcpy implementation (ARCH optimized or lib/string.c) when it is possible: + * - when dest is before src (assuming that memcpy is doing forward-copying) + * - when destination don't overlap the source buffer (src + count <= dest) + * + * WARNING: the first optimisation cause an issue, when __HAVE_ARCH_MEMCPY is defined, + * __HAVE_ARCH_MEMMOVE is not defined and if the memcpy ARCH-specific + * implementation is not doing a forward-copying. + * + * No issue today because memcpy is doing a forward-copying in lib/string.c and for ARM32 + * architecture; no other arches use __HAVE_ARCH_MEMCPY without __HAVE_ARCH_MEMMOVE. + */ memcpy(dest, src, count); } else { tmp = (char *) dest + count;