1/* 2 * Written by J.T. Conklin <jtc@NetBSD.org>. 3 * Public domain. 4 * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com> 5 */ 6 7#include <machine/asm.h> 8__FBSDID("$FreeBSD$"); 9 10#if 0 11 RCSID("$NetBSD: memcmp.S,v 1.2 2003/07/26 19:24:39 salo Exp $") 12#endif 13 14ENTRY(memcmp) 15 cld /* set compare direction forward */ 16 movq %rdx,%rcx /* compare by longs */ 17 shrq $3,%rcx 18 repe 19 cmpsq 20 jne L5 /* do we match so far? */ 21 22 movq %rdx,%rcx /* compare remainder by bytes */ 23 andq $7,%rcx 24 repe 25 cmpsb 26 jne L6 /* do we match? */ 27 28 xorl %eax,%eax /* we match, return zero */ 29 ret 30 31L5: movl $8,%ecx /* We know that one of the next */ 32 subq %rcx,%rdi /* eight pairs of bytes do not */ 33 subq %rcx,%rsi /* match. */ 34 repe 35 cmpsb 36L6: xorl %eax,%eax /* Perform unsigned comparison */ 37 movb -1(%rdi),%al 38 xorl %edx,%edx 39 movb -1(%rsi),%dl 40 subl %edx,%eax 41 ret 42