1 /* $OpenBSD: memcmp.S,v 1.1 2000/06/16 19:56:54 millert Exp $ */
2
3 /*
4 * Written by J.T. Conklin <jtc@netbsd.org>.
5 * Public domain.
6 */
7
8 #include <machine/asm.h>
9
10 ENTRY(memcmp)
11 pushl %edi
12 pushl %esi
13 movl 12(%esp),%edi
14 movl 16(%esp),%esi
15 cld /* set compare direction forward */
16
17 movl 20(%esp),%ecx /* compare by words */
18 shrl $2,%ecx
19 repe
20 cmpsl
21 jne L5 /* do we match so far? */
22
23 movl 20(%esp),%ecx /* compare remainder by bytes */
24 andl $3,%ecx
25 repe
26 cmpsb
27 jne L6 /* do we match? */
28
29 xorl %eax,%eax /* we match, return zero */
30 popl %esi
31 popl %edi
32 ret
33
34 L5: movl $4,%ecx /* We know that one of the next */
35 subl %ecx,%edi /* four pairs of bytes do not */
36 subl %ecx,%esi /* match. */
37 repe
38 cmpsb
39 L6: movzbl -1(%edi),%eax /* Perform unsigned comparison */
40 movzbl -1(%esi),%edx
41 subl %edx,%eax
42 popl %esi
43 popl %edi
44 ret