1 /* $OpenBSD: memcmp.S,v 1.4 2005/08/07 11:30:38 espie Exp $ */ 2 /* 3 * Written by J.T. Conklin <jtc (at) netbsd.org>. 4 * Public domain. 5 */ 6 7 #include <machine/asm.h> 8 9 ENTRY(memcmp) 10 pushl %edi 11 pushl %esi 12 movl 12(%esp),%edi 13 movl 16(%esp),%esi 14 cld /* set compare direction forward */ 15 16 movl 20(%esp),%ecx /* compare by words */ 17 shrl $2,%ecx 18 repe 19 cmpsl 20 jne L5 /* do we match so far? */ 21 22 movl 20(%esp),%ecx /* compare remainder by bytes */ 23 andl $3,%ecx 24 repe 25 cmpsb 26 jne L6 /* do we match? */ 27 28 xorl %eax,%eax /* we match, return zero */ 29 popl %esi 30 popl %edi 31 ret 32 33 L5: movl $4,%ecx /* We know that one of the next */ 34 subl %ecx,%edi /* four pairs of bytes do not */ 35 subl %ecx,%esi /* match. */ 36 repe 37 cmpsb 38 L6: movzbl -1(%edi),%eax /* Perform unsigned comparison */ 39 movzbl -1(%esi),%edx 40 subl %edx,%eax 41 popl %esi 42 popl %edi 43 ret 44
