i386/gen/bzero.s

   1 /*
   2  * Copyright (c) 2002 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1993 Winning Strategies, Inc.
  27  * All rights reserved.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by Winning Strategies, Inc.
  40  * 4. The name of the author may not be used to endorse or promote products
  41  *    derived from this software withough specific prior written permission
  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  44  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  45  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  46  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  47  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  48  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  49  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  50  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  51  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  52  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  53  *
  54  */
  55
  56 #include <architecture/i386/asm_help.h>
  57
  58 /*
  59  * bzero (void *b, size_t len)
  60  *      write len zero bytes to the string b.
  61  *
  62  * Written by:
  63  *      J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
  64  */
  65
  66 TEXT
  67 LEAF(_bzero,0)
  68         pushl   %edi
  69         pushl   %ebx
  70         movl    12(%esp),%edi
  71         movl    16(%esp),%ecx
  72
  73         cld                             /* set fill direction forward */
  74         xorl    %eax,%eax               /* set fill data to 0 */
  75
  76         /*
  77          * if the string is too short, it's really not worth the overhead
  78          * of aligning to word boundries, etc.  So we jump to a plain
  79          * unaligned set.
  80          */
  81         cmpl    $0x0f,%ecx
  82         jle     L1
  83
  84         movl    %edi,%edx               /* compute misalignment */
  85         negl    %edx
  86         andl    $3,%edx
  87         movl    %ecx,%ebx
  88         subl    %edx,%ebx
  89
  90         movl    %edx,%ecx               /* zero until word aligned */
  91         rep
  92         stosb
  93
  94         movl    %ebx,%ecx               /* zero by words */
  95         shrl    $2,%ecx
  96         rep
  97         stosl
  98
  99         movl    %ebx,%ecx
 100         andl    $3,%ecx                 /* zero remainder by bytes */
 101 L1:     rep
 102         stosb
 103
 104         popl    %ebx
 105         popl    %edi
 106 END(_bzero)