Improve bzero performance
Commit Message
Rather than using a C implementation of memset, directly call memset, which typically has a much
faster optimized implementation.
ChangeLog:
2015-01-12 Wilco Dijkstra wdijkstr@arm.com
* string/bzero.c (__bzero): Call memset for performance.
---
string/bzero.c | 58 +++-------------------------------------------------------
1 file changed, 3 insertions(+), 55 deletions(-)
Comments
This is fine. I think it's safe enough during the freeze, but there is no
burning (melting?) reason to rush it if folks are feeling conservative.
> +#include <stddef.h>
> #include <string.h>
Actually, there is no reason for this new #include. Drop it.
> Roland McGrath wrote:
> > +#include <stddef.h>
> > #include <string.h>
>
> Actually, there is no reason for this new #include. Drop it.
OK, committed without the include.
Wilco
@@ -16,67 +16,15 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <stddef.h>
#include <string.h>
-#include <memcopy.h>
#undef __bzero
/* Set N bytes of S to 0. */
void
-__bzero (s, len)
- void *s;
- size_t len;
+__bzero (void *s, size_t len)
{
- long int dstp = (long int) s;
- const op_t zero = 0;
-
- if (len >= 8)
- {
- size_t xlen;
-
- /* There are at least some bytes to zero. No need to test
- for LEN == 0 in this alignment loop. */
- while (dstp % OPSIZ != 0)
- {
- ((byte *) dstp)[0] = 0;
- dstp += 1;
- len -= 1;
- }
-
- /* Write 8 op_t per iteration until less than 8 op_t remain. */
- xlen = len / (OPSIZ * 8);
- while (xlen != 0)
- {
- ((op_t *) dstp)[0] = zero;
- ((op_t *) dstp)[1] = zero;
- ((op_t *) dstp)[2] = zero;
- ((op_t *) dstp)[3] = zero;
- ((op_t *) dstp)[4] = zero;
- ((op_t *) dstp)[5] = zero;
- ((op_t *) dstp)[6] = zero;
- ((op_t *) dstp)[7] = zero;
- dstp += 8 * OPSIZ;
- xlen -= 1;
- }
- len %= OPSIZ * 8;
-
- /* Write 1 op_t per iteration until less than op_t remain. */
- xlen = len / OPSIZ;
- while (xlen != 0)
- {
- ((op_t *) dstp)[0] = zero;
- dstp += OPSIZ;
- xlen -= 1;
- }
- len %= OPSIZ;
- }
-
- /* Write the last few bytes. */
- while (len != 0)
- {
- ((byte *) dstp)[0] = 0;
- dstp += 1;
- len -= 1;
- }
+ memset (s, '\0', len);
}
weak_alias (__bzero, bzero)