source: trunk/libs/newlib/src/newlib/libc/machine/microblaze/strlen.c @ 444

/* Copyright (c) 2009 Xilinx, Inc.  All rights reserved. 

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FUNCTION
        <<strlen>>---character string length
        
INDEX
        strlen

SYNOPSIS
        #include <string.h>
        size_t strlen(const char *<[str]>);

DESCRIPTION
        The <<strlen>> function works out the length of the string
        starting at <<*<[str]>>> by counting chararacters until it
        reaches a <<NULL>> character.

RETURNS
        <<strlen>> returns the character count.

PORTABILITY
<<strlen>> is ANSI C.

<<strlen>> requires no supporting OS subroutines.

QUICKREF
        strlen ansi pure
*/

#include <_ansi.h>
#include <string.h>
#include <limits.h>

#define LBLOCKSIZE   (sizeof (long))
#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))

#if LONG_MAX == 2147483647L
#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
#else
#if LONG_MAX == 9223372036854775807L
/* Nonzero if X (a long int) contains a NULL byte. */
#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
#else
#error long int is not a 32bit or 64bit type.
#endif
#endif

#ifndef DETECTNULL
#error long int is not a 32bit or 64bit byte
#endif

size_t
strlen (const char *str)
{

#ifndef HAVE_HW_PCMP

#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  const char *start = str;

  while (*str)
    str++;

  return str - start;
#else
  const char *start = str;
  unsigned long *aligned_addr;

  if (!UNALIGNED (str))
    {
      /* If the string is word-aligned, we can check for the presence of 
         a null in each word-sized block.  */
      aligned_addr = (unsigned long*)str;
      while (!DETECTNULL (*aligned_addr))
        aligned_addr++;

      /* Once a null is detected, we check each byte in that block for a
         precise position of the null.  */
      str = (char*)aligned_addr;
    }
 
  while (*str)
    str++;
  return str - start;
#endif /* not PREFER_SIZE_OVER_SPEED */

#else

#include "mb_endian.h"

  asm volatile ("                                               \n\
        or      r9, r0, r0              /* Index register */    \n\
check_alignment:                                                \n\
        andi    r3, r5, 3                                       \n\
        bnei    r3, align_arg                                   \n\
len_loop:                                                       \n"
        LOAD4BYTES("r3", "r5", "r9")
"                                                               \n\
        pcmpbf  r4, r3, r0                                      \n\
        bnei    r4, end_len                                     \n\
        brid    len_loop                                        \n\
        addik   r9, r9, 4                                       \n\
end_len:                                                        \n\
        lbu     r3, r5, r9                                      \n\
        beqi    r3, done_len                                    \n\
        brid    end_len                                         \n\
        addik   r9, r9, 1                                       \n\
done_len:                                                       \n\
        rtsd    r15, 8                                          \n\
        or      r3, r0, r9              /* Return len */        \n\
align_arg:                                                      \n\
        rsubik  r10, r3, 4                                      \n\
align_loop:                                                     \n\
        lbu     r3, r5, r9                                      \n\
        beqid   r3, done_len                                    \n\
        addik   r10, r10, -1                                    \n\
        bneid   r10, align_loop                                 \n\
        addik   r9, r9, 1                                       \n\
        bri     len_loop");

#endif  /* ! HAVE_HW_PCMP */
}