sysdeps/i386/strpbrk.S

   1 /* strcspn (str, ss) -- Return the length of the initial segement of STR
   2                         which contains no characters from SS.
   3    For Intel 80x86, x>=3.
   4    Copyright (C) 1994-2019 Free Software Foundation, Inc.
   5    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>
   6    Bug fixes by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au>
   7    This file is part of the GNU C Library.
   8
   9    The GNU C Library is free software; you can redistribute it and/or
  10    modify it under the terms of the GNU Lesser General Public
  11    License as published by the Free Software Foundation; either
  12    version 2.1 of the License, or (at your option) any later version.
  13
  14    The GNU C Library is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17    Lesser General Public License for more details.
  18
  19    You should have received a copy of the GNU Lesser General Public
  20    License along with the GNU C Library; if not, see
  21    <https://www.gnu.org/licenses/>.  */
  22
  23 #include <sysdep.h>
  24 #include "asm-syntax.h"
  25
  26 #define PARMS   4               /* no space for saved regs */
  27 #define RTN     PARMS
  28 #define STR     RTN
  29 #define STOP    STR+4
  30
  31         .text
  32 ENTRY (strpbrk)
  33
  34         movl STR(%esp), %edx
  35         movl STOP(%esp), %eax
  36
  37         /* First we create a table with flags for all possible characters.
  38            For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
  39            supported by the C string functions we have 256 characters.
  40            Before inserting marks for the stop characters we clear the whole
  41            table.  The unrolled form is much faster than a loop.  */
  42         xorl %ecx, %ecx         /* %ecx = 0 !!! */
  43
  44         pushl %ecx              /* make a 256 bytes long block filled with 0 */
  45         cfi_adjust_cfa_offset (4)
  46         pushl %ecx
  47         cfi_adjust_cfa_offset (4)
  48         pushl %ecx
  49         cfi_adjust_cfa_offset (4)
  50         pushl %ecx
  51         cfi_adjust_cfa_offset (4)
  52         pushl %ecx
  53         cfi_adjust_cfa_offset (4)
  54         pushl %ecx
  55         cfi_adjust_cfa_offset (4)
  56         pushl %ecx
  57         cfi_adjust_cfa_offset (4)
  58         pushl %ecx
  59         cfi_adjust_cfa_offset (4)
  60         pushl %ecx
  61         cfi_adjust_cfa_offset (4)
  62         pushl %ecx
  63         cfi_adjust_cfa_offset (4)
  64         pushl %ecx
  65         cfi_adjust_cfa_offset (4)
  66         pushl %ecx
  67         cfi_adjust_cfa_offset (4)
  68         pushl %ecx
  69         cfi_adjust_cfa_offset (4)
  70         pushl %ecx
  71         cfi_adjust_cfa_offset (4)
  72         pushl %ecx
  73         cfi_adjust_cfa_offset (4)
  74         pushl %ecx
  75         cfi_adjust_cfa_offset (4)
  76         pushl %ecx
  77         cfi_adjust_cfa_offset (4)
  78         pushl %ecx
  79         cfi_adjust_cfa_offset (4)
  80         pushl %ecx
  81         cfi_adjust_cfa_offset (4)
  82         pushl %ecx
  83         cfi_adjust_cfa_offset (4)
  84         pushl %ecx
  85         cfi_adjust_cfa_offset (4)
  86         pushl %ecx
  87         cfi_adjust_cfa_offset (4)
  88         pushl %ecx
  89         cfi_adjust_cfa_offset (4)
  90         pushl %ecx
  91         cfi_adjust_cfa_offset (4)
  92         pushl %ecx
  93         cfi_adjust_cfa_offset (4)
  94         pushl %ecx
  95         cfi_adjust_cfa_offset (4)
  96         pushl %ecx
  97         cfi_adjust_cfa_offset (4)
  98         pushl %ecx
  99         cfi_adjust_cfa_offset (4)
 100         pushl %ecx
 101         cfi_adjust_cfa_offset (4)
 102         pushl %ecx
 103         cfi_adjust_cfa_offset (4)
 104         pushl %ecx
 105         cfi_adjust_cfa_offset (4)
 106         pushl %ecx
 107         cfi_adjust_cfa_offset (4)
 108         pushl %ecx
 109         cfi_adjust_cfa_offset (4)
 110         pushl %ecx
 111         cfi_adjust_cfa_offset (4)
 112         pushl %ecx
 113         cfi_adjust_cfa_offset (4)
 114         pushl %ecx
 115         cfi_adjust_cfa_offset (4)
 116         pushl %ecx
 117         cfi_adjust_cfa_offset (4)
 118         pushl %ecx
 119         cfi_adjust_cfa_offset (4)
 120         pushl %ecx
 121         cfi_adjust_cfa_offset (4)
 122         pushl %ecx
 123         cfi_adjust_cfa_offset (4)
 124         pushl %ecx
 125         cfi_adjust_cfa_offset (4)
 126         pushl %ecx
 127         cfi_adjust_cfa_offset (4)
 128         pushl %ecx
 129         cfi_adjust_cfa_offset (4)
 130         pushl %ecx
 131         cfi_adjust_cfa_offset (4)
 132         pushl %ecx
 133         cfi_adjust_cfa_offset (4)
 134         pushl %ecx
 135         cfi_adjust_cfa_offset (4)
 136         pushl %ecx
 137         cfi_adjust_cfa_offset (4)
 138         pushl %ecx
 139         cfi_adjust_cfa_offset (4)
 140         pushl %ecx
 141         cfi_adjust_cfa_offset (4)
 142         pushl %ecx
 143         cfi_adjust_cfa_offset (4)
 144         pushl %ecx
 145         cfi_adjust_cfa_offset (4)
 146         pushl %ecx
 147         cfi_adjust_cfa_offset (4)
 148         pushl %ecx
 149         cfi_adjust_cfa_offset (4)
 150         pushl %ecx
 151         cfi_adjust_cfa_offset (4)
 152         pushl %ecx
 153         cfi_adjust_cfa_offset (4)
 154         pushl %ecx
 155         cfi_adjust_cfa_offset (4)
 156         pushl %ecx
 157         cfi_adjust_cfa_offset (4)
 158         pushl %ecx
 159         cfi_adjust_cfa_offset (4)
 160         pushl $0                /* These immediate values make the label 2 */
 161         cfi_adjust_cfa_offset (4)
 162         pushl $0                /* to be aligned on a 16 byte boundary to */
 163         cfi_adjust_cfa_offset (4)
 164         pushl $0                /* get a better performance of the loop.  */
 165         cfi_adjust_cfa_offset (4)
 166         pushl $0
 167         cfi_adjust_cfa_offset (4)
 168         pushl $0
 169         cfi_adjust_cfa_offset (4)
 170         pushl $0
 171         cfi_adjust_cfa_offset (4)
 172
 173 /* For understanding the following code remember that %ecx == 0 now.
 174    Although all the following instruction only modify %cl we always
 175    have a correct zero-extended 32-bit value in %ecx.  */
 176
 177 /* Don't change the "testb $0xff,%%cl" to "testb %%cl,%%cl".  We want
 178    longer instructions so that the next loop aligns without adding nops.  */
 179
 180 L(2):   movb (%eax), %cl        /* get byte from stopset */
 181         testb %cl, %cl          /* is NUL char? */
 182         jz L(1)                 /* yes => start compare loop */
 183         movb %cl, (%esp,%ecx)   /* set corresponding byte in stopset table */
 184
 185         movb 1(%eax), %cl       /* get byte from stopset */
 186         testb $0xff, %cl        /* is NUL char? */
 187         jz L(1)                 /* yes => start compare loop */
 188         movb %cl, (%esp,%ecx)   /* set corresponding byte in stopset table */
 189
 190         movb 2(%eax), %cl       /* get byte from stopset */
 191         testb $0xff, %cl        /* is NUL char? */
 192         jz L(1)                 /* yes => start compare loop */
 193         movb %cl, (%esp,%ecx)   /* set corresponding byte in stopset table */
 194
 195         movb 3(%eax), %cl       /* get byte from stopset */
 196         addl $4, %eax           /* increment stopset pointer */
 197         movb %cl, (%esp,%ecx)   /* set corresponding byte in stopset table */
 198         testb $0xff, %cl        /* is NUL char? */
 199         jnz L(2)                /* no => process next dword from stopset */
 200
 201 L(1):   leal -4(%edx), %eax     /* prepare loop */
 202
 203         /* We use a neat trick for the following loop.  Normally we would
 204            have to test for two termination conditions
 205            1. a character in the stopset was found
 206            and
 207            2. the end of the string was found
 208            But as a sign that the character is in the stopset we store its
 209            value in the table.  But the value of NUL is NUL so the loop
 210            terminates for NUL in every case.  */
 211
 212 L(3):   addl $4, %eax           /* adjust pointer for full loop round */
 213
 214         movb (%eax), %cl        /* get byte from string */
 215         cmpb %cl, (%esp,%ecx)   /* is it contained in stopset? */
 216         je L(4)                 /* yes => return */
 217
 218         movb 1(%eax), %cl       /* get byte from string */
 219         cmpb %cl, (%esp,%ecx)   /* is it contained in stopset? */
 220         je L(5)                 /* yes => return */
 221
 222         movb 2(%eax), %cl       /* get byte from string */
 223         cmpb %cl, (%esp,%ecx)   /* is it contained in stopset? */
 224         je L(6)                 /* yes => return */
 225
 226         movb 3(%eax), %cl       /* get byte from string */
 227         cmpb %cl, (%esp,%ecx)   /* is it contained in stopset? */
 228         jne L(3)                        /* yes => return */
 229
 230         incl %eax               /* adjust pointer */
 231 L(6):   incl %eax
 232 L(5):   incl %eax
 233
 234 L(4):   addl $256, %esp         /* remove stopset */
 235         cfi_adjust_cfa_offset (-256)
 236
 237         orb %cl, %cl            /* was last character NUL? */
 238         jnz L(7)                /* no => return pointer */
 239         xorl %eax, %eax
 240
 241 L(7):   ret
 242 END (strpbrk)
 243 libc_hidden_builtin_def (strpbrk)