strlen.c

/*
 * strlen.c -- strlen function.  On at least some MIPS chips, a simple
 * strlen is faster than the 'optimized' C version.
 *
 * Copyright (c) 2001, 2002 Red Hat, Inc.
 *
 * The authors hereby grant permission to use, copy, modify, distribute,
 * and license this software and its documentation for any purpose, provided
 * that existing copyright notices are retained in all copies and that this
 * notice is included verbatim in any distributions. No written agreement,
 * license, or royalty fee is required for any of the authorized uses.
 * Modifications to this software may be copyrighted by their authors
 * and need not follow the licensing terms described here, provided that
 * the new terms are clearly indicated on the first page of each file where
 * they apply.
 */
 
#include <stddef.h>
#include <string.h>
 
/* MIPS16 needs to come first.  */
 
#if defined(__mips16)
size_t
strlen (const char *str)
{
  const char *start = str;
 
  while (*str++ != '\0')
    ;
 
  return str - start - 1;
}
#elif defined(__mips64)
__asm__(""          /* 64-bit MIPS targets */
    "   .set    noreorder\n"
    "   .set    nomacro\n"
    "   .globl  strlen\n"
    "   .ent    strlen\n"
    "strlen:\n"
    "   daddiu  $2,$4,1\n"
    "\n"
    "1: lbu $3,0($4)\n"
    "   bnez    $3,1b\n"
    "   daddiu  $4,$4,1\n"
    "\n"
    "   jr  $31\n"
    "   dsubu   $2,$4,$2\n"
    "   .end    strlen\n"
    "   .set    macro\n"
    "   .set    reorder\n");
 
#else
__asm__(""          /* 32-bit MIPS targets */
    "   .set    noreorder\n"
    "   .set    nomacro\n"
    "   .globl  strlen\n"
    "   .ent    strlen\n"
    "strlen:\n"
    "   addiu   $2,$4,1\n"
    "\n"
    "1: lbu $3,0($4)\n"
#if defined(_R3000)
    "   nop \n"
#endif
    "   bnez    $3,1b\n"
    "   addiu   $4,$4,1\n"
    "\n"
    "   jr  $31\n"
    "   subu    $2,$4,$2\n"
    "   .end    strlen\n"
    "   .set    macro\n"
    "   .set    reorder\n");
#endif