usr/src/lib/libc/amd64/gen/strrchr.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  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26         .file   "strrchr.s"
  27
  28 /
  29 / strrchr(sp, c)
  30 /
  31 / Returns the pointer in sp at which the character c last
  32 / appears; NULL if no found
  33 /
  34 / Fast assembly language version of the following C-program strrchr
  35 / which represents the `standard' for the C-library.
  36 /
  37 /       char *
  38 /       strrchr(const char *sp, int c)
  39 /       {
  40 /               char    *r = NULL;
  41 /
  42 /               do {
  43 /                       if (*sp == (char)c)
  44 /                               r = (char *)sp;
  45 /               } while (*sp++);
  46 /
  47 /               return (r);
  48 /       }
  49 /
  50
  51 #include "SYS.h"
  52
  53         ENTRY(strrchr)          /* (char *s, int c) */
  54         movl    $0, %eax        / %rax = NULL (current occurrence)
  55         movl    %esi, %ecx      / %cl == char to search for
  56         testq   $3, %rdi        / if %rdi not word aligned
  57         jnz     .L1             / goto .L1
  58         .align  4
  59 .L3:
  60         movl    (%rdi), %edx    / move 1 word from (%rdi) to %edx
  61         cmpb    %cl, %dl        / if the fist byte is not %cl
  62         jne     .L4             / goto .L4
  63         movq    %rdi, %rax      / save this address to %rax
  64 .L4:
  65         cmpb    $0, %dl         / if a null termination
  66         je      .L8             / goto .L8
  67
  68         cmpb    %cl, %dh        / if the second byte is not %cl
  69         jne     .L5             / goto .L5
  70         leaq    1(%rdi), %rax   / save this address to %rax
  71 .L5:
  72         cmpb    $0, %dh         / if a null termination
  73         je      .L8             / goto .L8
  74
  75         shrl    $16, %edx       / right shift 16-bit
  76         cmpb    %cl, %dl        / if the third byte is not %cl
  77         jne     .L6             / goto .L6
  78         leaq    2(%rdi), %rax   / save this address to %rax
  79 .L6:
  80         cmpb    $0, %dl         / if a null termination
  81         je      .L8             / goto .L8
  82
  83         cmpb    %cl, %dh        / if the fourth byte is not %cl
  84         jne     .L7             / goto .L7
  85         leaq    3(%rdi), %rax   / save this address to %rax
  86 .L7:
  87         cmpb    $0, %dh         / if a null termination
  88         je      .L8             / goto .L8
  89
  90         addq    $4, %rdi        / next word
  91         jmp     .L3             / goto .L3
  92         .align  4
  93 .L1:
  94         movb    (%rdi), %dl     / move 1 byte from (%rdi) to %dl
  95         cmpb    %cl, %dl        / if %dl is not %cl
  96         jne     .L2             / goto .L2
  97         movq    %rdi, %rax      / save this address to %rax
  98 .L2:
  99         cmpb    $0, %dl         / if a null termination
 100         je      .L8             / goto .L8
 101
 102         incq    %rdi            / next byte
 103         testq   $3, %rdi        / if %rdi not word aligned
 104         jnz     .L1             / goto .L1
 105         jmp     .L3             / goto .L3 (word aligned)
 106         .align  4
 107 .L8:
 108         ret                     / %rax points to the last occurrence or NULL
 109         SET_SIZE(strrchr)