1 /* $OpenBSD: bzero.S,v 1.7 2022年12月04日 08:22:13 tb Exp $ */ 2 /* 3 * Written by J.T. Conklin <jtc@netbsd.org>. 4 * Public domain. 5 */ 6 7#include "DEFS.h" 8 9 ENTRY_NB(bzero) 10 pushl %edi 11 movl 8(%esp),%edi 12 movl 12(%esp),%edx 13 14 cld /* set fill direction forward */ 15 xorl %eax,%eax /* set fill data to 0 */ 16 17 /* 18 * if the string is too short, it's really not worth the overhead 19 * of aligning to word boundaries, etc. So we jump to a plain 20 * unaligned set. 21 */ 22 cmpl $16,%edx 23 jb L1 24 25 movl %edi,%ecx /* compute misalignment */ 26 negl %ecx 27 andl $3,%ecx 28 subl %ecx,%edx 29 rep /* zero until word aligned */ 30 stosb 31 32 movl %edx,%ecx /* zero by words */ 33 shrl $2,%ecx 34 andl $3,%edx 35 rep 36 stosl 37 38 L1: movl %edx,%ecx /* zero remainder by bytes */ 39 rep 40 stosb 41 42 popl %edi 43 ret 44 END_WEAK(bzero) 45