newlib/libc/machine/mips/strlen.c

   1 /*
   2  * strlen.c -- strlen function.  On at least some MIPS chips, a simple
   3  * strlen is faster than the 'optimized' C version.
   4  *
   5  * Copyright (c) 2001, 2002 Red Hat, Inc.
   6  *
   7  * The authors hereby grant permission to use, copy, modify, distribute,
   8  * and license this software and its documentation for any purpose, provided
   9  * that existing copyright notices are retained in all copies and that this
  10  * notice is included verbatim in any distributions. No written agreement,
  11  * license, or royalty fee is required for any of the authorized uses.
  12  * Modifications to this software may be copyrighted by their authors
  13  * and need not follow the licensing terms described here, provided that
  14  * the new terms are clearly indicated on the first page of each file where
  15  * they apply.
  16  */
  17
  18 #include <stddef.h>
  19 #include <string.h>
  20
  21 /* MIPS16 needs to come first.  */
  22
  23 #if defined(__mips16)
  24 size_t
  25 strlen (const char *str)
  26 {
  27   const char *start = str;
  28
  29   while (*str++ != '\0')
  30     ;
  31
  32   return str - start - 1;
  33 }
  34 #elif defined(__mips64)
  35 __asm__(""                      /* 64-bit MIPS targets */
  36         "       .set    noreorder\n"
  37         "       .set    nomacro\n"
  38         "       .globl  strlen\n"
  39         "       .ent    strlen\n"
  40         "strlen:\n"
  41         "       daddiu  $2,$4,1\n"
  42         "\n"
  43         "1:     lbu     $3,0($4)\n"
  44         "       bnez    $3,1b\n"
  45         "       daddiu  $4,$4,1\n"
  46         "\n"
  47         "       jr      $31\n"
  48         "       dsubu   $2,$4,$2\n"
  49         "       .end    strlen\n"
  50         "       .set    macro\n"
  51         "       .set    reorder\n");
  52
  53 #else
  54 __asm__(""                      /* 32-bit MIPS targets */
  55         "       .set    noreorder\n"
  56         "       .set    nomacro\n"
  57         "       .globl  strlen\n"
  58         "       .ent    strlen\n"
  59         "strlen:\n"
  60         "       addiu   $2,$4,1\n"
  61         "\n"
  62         "1:     lbu     $3,0($4)\n"
  63 #if defined(_R3000)
  64         "       nop     \n"
  65 #endif
  66         "       bnez    $3,1b\n"
  67         "       addiu   $4,$4,1\n"
  68         "\n"
  69         "       jr      $31\n"
  70         "       subu    $2,$4,$2\n"
  71         "       .end    strlen\n"
  72         "       .set    macro\n"
  73         "       .set    reorder\n");
  74 #endif