usr/src/lib/libc/amd64/gen/memccpy.s

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27         .file   "memccpy.s"
  28
  29 #include <sys/asm_linkage.h>
  30
  31         ANSI_PRAGMA_WEAK(memccpy,function)
  32
  33         ENTRY(memccpy)  /* (void *dst, void *src, uchar_t c, size_t) */
  34 .loop:
  35         decq    %rcx            / decrement bytes to go
  36         jl      .notfound
  37         movb    (%rsi),%dh
  38         movb    %dh,(%rdi)      / move byte
  39         cmpb    %dh,%dl         / is it the byte sought?
  40         je      .found          / yes
  41
  42         decq    %rcx            / decrement bytes to go
  43         jl      .notfound
  44         movb    1(%rsi),%dh
  45         movb    %dh,1(%rdi)     / move byte
  46         cmpb    %dh,%dl         / is it the byte sought?
  47         je      .found1         / yes
  48
  49         decq    %rcx            / decrement bytes to go
  50         jl      .notfound
  51         movb    2(%rsi),%dh
  52         movb    %dh,2(%rdi)     / move byte
  53         cmpb    %dh,%dl         / is it the byte sought?
  54         je      .found2         / yes
  55
  56         decq    %rcx            / decrement bytes to go
  57         jl      .notfound
  58         movb    3(%rsi),%dh
  59         movb    %dh,3(%rdi)     / move byte
  60         addq    $4,%rsi
  61         addq    $4,%rdi
  62         cmpb    %dh,%dl         / is it the byte sought?
  63         jne     .loop           / no
  64         decq    %rdi
  65
  66 .found:
  67         incq    %rdi            / return pointer to next byte in dest
  68         movq    %rdi,%rax
  69         ret
  70
  71         .align  4
  72 .found2:
  73         incq    %rdi
  74 .found1:
  75         addq    $2,%rdi         / return pointer to next byte in dest
  76         movq    %rdi,%rax
  77         ret
  78
  79         .align  4
  80 .notfound:
  81         xorl    %eax,%eax       / search fails
  82         ret
  83         SET_SIZE(memccpy)