/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

        .file   "strncmp.s"

#include "SYS.h"

        ENTRY(strncmp)
        pushl   %esi            / save register variables
        movl    8(%esp),%esi    / %esi = first string
        movl    %edi,%edx
        movl    12(%esp),%edi   / %edi = second string
        cmpl    %esi,%edi       / same string?
        je      .equal
        movl    16(%esp),%ecx   / %ecx = length
        incl    %ecx            / will later predecrement this uint
.loop:
        decl    %ecx
        je      .equal          / Used all n chars?
        movb    (%esi),%al      / slodb ; scab
        cmpb    (%edi),%al
        jne     .notequal_0     / Are the bytes equal?
        testb   %al,%al
        je      .equal          / End of string?

        decl    %ecx
        je      .equal          / Used all n chars?
        movb    1(%esi),%al     / slodb ; scab
        cmpb    1(%edi),%al
        jne     .notequal_1     / Are the bytes equal?
        testb   %al,%al
        je      .equal          / End of string?

        decl    %ecx
        je      .equal          / Used all n chars?
        movb    2(%esi),%al     / slodb ; scab
        cmpb    2(%edi),%al
        jne     .notequal_2     / Are the bytes equal?
        testb   %al,%al
        je      .equal          / End of string?

        decl    %ecx
        je      .equal          / Used all n chars?
        movb    3(%esi),%al     / slodb ; scab
        cmpb    3(%edi),%al
        jne     .notequal_3     / Are the bytes equal?
        addl    $4,%esi
        addl    $4,%edi
        testb   %al,%al
        jne     .loop           / End of string?

.equal:
        popl    %esi            / restore registers
        xorl    %eax,%eax       / return 0
        movl    %edx,%edi
        ret

        .align  4
.notequal_3:
        incl    %edi
.notequal_2:
        incl    %edi
.notequal_1:
        incl    %edi
.notequal_0:
        popl    %esi            / restore registers
        clc                     / clear carry bit
        subb    (%edi),%al
        movl    %edx,%edi
        movl    $-1, %eax       / possibly wasted instr
        jc      .neg            / did we overflow in the sub
        movl    $1, %eax        / if not a > b
.neg:
        ret
        SET_SIZE(strncmp)