Return to memcmp.S CVS log

Up to [local] / sys / lib / libkern / arch / amd64

Initial revision

/*
 * Written by J.T. Conklin <jtc@netbsd.org>.
 * Public domain.
 * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
 */

#include <machine/asm.h>

#if defined(LIBC_SCCS)
	RCSID("$NetBSD: memcmp.S,v 1.1 2001/06/19 00:22:46 fvdl Exp $")
#endif

ENTRY(memcmp)
	cld				/* set compare direction forward */
	movq	%rdx,%rcx		/* compare by longs */
	shrq	$3,%rcx
	repe
	cmpsq
	jne	L5			/* do we match so far? */

	movq	%rdx,%rcx		/* compare remainder by bytes */
	andq	$7,%rcx
	repe
	cmpsb
	jne	L6			/* do we match? */

	xorl	%eax,%eax		/* we match, return zero	*/
	ret

L5:	movl	$8,%ecx			/* We know that one of the next	*/
	subq	%rcx,%rdi		/* eight pairs of bytes do not	*/
	subq	%rcx,%rsi		/* match.			*/
	repe
	cmpsb
L6:	xorl	%eax,%eax		/* Perform unsigned comparison	*/
	movb	-1(%rdi),%al
	xorl	%edx,%edx
	movb	-1(%rsi),%dl
	subl    %edx,%eax
	ret