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Be smarter about handling overlapped copies and only go backwards if it

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is really necessary. Going backwards on a P6 is much slower than forwards
and it's a little slower on a P5. Also moved the count mask and 'std'
down a few lines - it's a couple percent faster this way on a P5.
This commit is contained in:
David Greenman 1995-12-27 18:47:45 +00:00
parent dfe11c5d9d
commit aacd7f348e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=13064
2 changed files with 16 additions and 12 deletions
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14
lib/libc/i386/string/bcopy.S
View File

@ -32,12 +32,12 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: bcopy.S,v 1.1 1994/08/05 01:18:24 wollman Exp $
* $Id: bcopy.S,v 1.2 1995/01/23 01:28:49 davidg Exp $
*/
#if defined(LIBC_RCS) && !defined(lint)
.text
.asciz "$Id: bcopy.S,v 1.1 1994/08/05 01:18:24 wollman Exp $"
.asciz "$Id: bcopy.S,v 1.2 1995/01/23 01:28:49 davidg Exp $"
#endif /* LIBC_RCS and not lint */
#include "DEFS.h"
@ -53,8 +53,10 @@ ENTRY(bcopy)
movl 12(%esp),%esi
movl 16(%esp),%edi
movl 20(%esp),%ecx
cmpl %esi,%edi /* potentially overlapping? */
jnb 1f
movl %edi,%eax
subl %esi,%eax
cmpl %ecx,%eax /* overlapping? */
jb 1f
cld /* nope, copy forwards. */
shrl $2,%ecx /* copy by words */
rep
@ -69,10 +71,10 @@ ENTRY(bcopy)
1:
addl %ecx,%edi /* copy backwards. */
addl %ecx,%esi
std
andl $3,%ecx /* any fractional bytes? */
decl %edi
decl %esi
andl $3,%ecx /* any fractional bytes? */
std
rep
movsb
movl 20(%esp),%ecx /* copy remainder by words */

14
lib/libc/i386/string/memmove.S
View File

@ -32,12 +32,12 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: memmove.S,v 1.1 1994/08/05 01:18:29 wollman Exp $
* $Id: memmove.S,v 1.2 1995/01/23 01:29:02 davidg Exp $
*/
#if defined(LIBC_RCS) && !defined(lint)
.text
.asciz "$Id: memmove.S,v 1.1 1994/08/05 01:18:29 wollman Exp $"
.asciz "$Id: memmove.S,v 1.2 1995/01/23 01:29:02 davidg Exp $"
#endif /* LIBC_RCS and not lint */
#include "DEFS.h"
@ -54,8 +54,10 @@ ENTRY(memmove)
movl 12(%esp),%edi
movl 16(%esp),%esi
movl 20(%esp),%ecx
cmpl %esi,%edi /* potentially overlapping? */
jnb 1f
movl %edi,%eax
subl %esi,%eax
cmpl %ecx,%eax
jb 1f
cld /* nope, copy forwards. */
shrl $2,%ecx /* copy by words */
rep
@ -71,10 +73,10 @@ ENTRY(memmove)
1:
addl %ecx,%edi /* copy backwards. */
addl %ecx,%esi
std
andl $3,%ecx /* any fractional bytes? */
decl %edi
decl %esi
andl $3,%ecx /* any fractional bytes? */
std
rep
movsb
movl 20(%esp),%ecx /* copy remainder by words */