u-boot-bounces@lists.denx.de wrote on 10/10/2009 11:51:16:

From:

Alessandro Rubini rubini-list@gnudd.com

To:

u-boot@lists.denx.de

Cc:

STEricsson_nomadik_linux@list.st.com, andrea.gallo@stericsson.com

Date:

10/10/2009 11:51

Subject:

[U-Boot] [PATCH V4 2/3] lib_generic memset: fill one word at a time if possible

Sent by:

u-boot-bounces@lists.denx.de

From: Alessandro Rubini rubini@unipv.it

If the destination is aligned, fill ulong values until possible. Then fill remaining part by byte.

Signed-off-by: Alessandro Rubini rubini@unipv.it Acked-by: Andrea Gallo andrea.gallo@stericsson.com Acked-by: Mike Frysinger vapier@gentoo.org

---

lib_generic/string.c | 22 +++++++++++++++++++--- 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/lib_generic/string.c b/lib_generic/string.c index 61a45dc..b375b81 100644 --- a/lib_generic/string.c +++ b/lib_generic/string.c @@ -403,10 +403,26 @@ char *strswab(const char *s) */ void * memset(void * s,int c,size_t count) {

• char *xs = (char *) s;

• unsigned long *sl = (unsigned long *) s;
• unsigned long cl = 0;
• char *s8;
• int i;
• /* do it one word at a time (32 bits or 64 bits) while possible */
• if ( ((ulong)s & (sizeof(*sl) - 1)) == 0) {

•  for (i = 0; i < sizeof(*sl); i++) {
  

•     cl <<= 8;
  

•     cl |= c & 0xff;
  

•  }
  

•  while (count >= sizeof(*sl)) {
  

•     *sl++ = cl;
  

•     count -= sizeof(*sl);
  

•  }
  

The above while can be slow if not the complier manages to turn into: for(wc = count / sizeof(*sl); wc; --wc) { *sl++ = cl; } count = count & (sizeof(*sl)-1);

even better would be: for(--sl, wc = count / sizeof(*sl); wc; --wc) { *++sl = cl; } ++sl; count = count & (sizeof(*sl)-1); for those arch's that can do pre inc and load/store in one instruction.

Just figured I should mention it.