uclibc-ng/libc/string/cris/memcpy.c

/* Copyright (C) 2001, 2003 Free Software Foundation, Inc.
   Copyright (C) 1994, 1995, 2000 Axis Communications AB.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

/*#************************************************************************#*/
/*#-------------------------------------------------------------------------*/
/*#                                                                         */
/*# FUNCTION NAME: memcpy()                                                 */
/*#                                                                         */
/*# PARAMETERS:  void* dst;   Destination address.                          */
/*#              void* src;   Source address.                               */
/*#              int   len;   Number of bytes to copy.                      */
/*#                                                                         */
/*# RETURNS:     dst.                                                       */
/*#                                                                         */
/*# DESCRIPTION: Copies len bytes of memory from src to dst.  No guarantees */
/*#              about copying of overlapping memory areas. This routine is */
/*#              very sensitive to compiler changes in register allocation. */
/*#              Should really be rewritten to avoid this problem.          */
/*#                                                                         */
/*#-------------------------------------------------------------------------*/
/*#                                                                         */
/*# HISTORY                                                                 */
/*#                                                                         */
/*# DATE      NAME            CHANGES                                       */
/*# ----      ----            -------                                       */
/*# 941007    Kenny R         Creation                                      */
/*# 941011    Kenny R         Lots of optimizations and inlining.           */
/*# 941129    Ulf A           Adapted for use in libc.                      */
/*# 950216    HP              N==0 forgotten if non-aligned src/dst.        */
/*#                           Added some optimizations.                     */
/*# 001025    HP              Make src and dst char *.  Align dst to	    */
/*#			      dword, not just word-if-both-src-and-dst-	    */
/*#			      are-misaligned.				    */
/*# 070806    RW              Modified for uClibc                           */
/*#                           (__arch_v32 -> __CONFIG_CRISV32__,            */
/*#                           include features.h to reach it.)              */
/*#                                                                         */
/*#-------------------------------------------------------------------------*/

#include <features.h>

#ifdef __CONFIG_CRISV32__
/* For CRISv32, movem is very cheap.  */
#define MEMCPY_BLOCK_THRESHOLD (44)
#else
/* Break even between movem and move16 is at 38.7*2, but modulo 44. */
#define MEMCPY_BLOCK_THRESHOLD (44*2)
#endif

void *memcpy(void *, const void *, unsigned int);

libc_hidden_proto(memcpy)
void *memcpy(void *pdst,
             const void *psrc,
             unsigned int pn)
{
  /* Ok.  Now we want the parameters put in special registers.
     Make sure the compiler is able to make something useful of this.
      As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).

     If gcc was allright, it really would need no temporaries, and no
     stack space to save stuff on. */

#ifndef MEMPCPY
  register void *return_dst __asm__ ("r10") = pdst;
#else
  /* FIXME: Use R10 for something.  */
# define return_dst dst
#endif

  register char *dst __asm__ ("r13") = pdst;
  register char *src __asm__ ("r11") = (char *) psrc;
  register int n __asm__ ("r12") = pn;
  
 
  /* When src is aligned but not dst, this makes a few extra needless
     cycles.  I believe it would take as many to check that the
     re-alignment was unnecessary.  */
  if (((unsigned long) dst & 3) != 0
      /* Don't align if we wouldn't copy more than a few bytes; so we
	 don't have to check further for overflows.  */
      && n >= 3)
  {
    if ((unsigned long) dst & 1)
    {
      n--;
      *(char*)dst = *(char*)src;
      src++;
      dst++;
    }

    if ((unsigned long) dst & 2)
    {
      n -= 2;
      *(short*)dst = *(short*)src;
      src += 2;
      dst += 2;
    }
  }

  /* Decide which copying method to use. */
  if (n >= MEMCPY_BLOCK_THRESHOLD)
  {
    /* For large copies we use 'movem' */

  /* It is not optimal to tell the compiler about clobbering any
     registers; that will move the saving/restoring of those registers
     to the function prologue/epilogue, and make non-movem sizes
     suboptimal.

      This method is not foolproof; it assumes that the "register asm"
     declarations at the beginning of the function really are used
     here (beware: they may be moved to temporary registers).
      This way, we do not have to save/move the registers around into
     temporaries; we can safely use them straight away.  */
    __asm__ __volatile__ ("\
	.syntax no_register_prefix					\n\
									\n\
        ;; Check that the register asm declaration got right.		\n\
        ;; The GCC manual explicitly says TRT will happen.		\n\
	.ifnc %0-%1-%2,$r13-$r11-$r12					\n\
	.err								\n\
	.endif								\n\
									\n\
	;; Save the registers we'll use in the movem process		\n\
	;; on the stack.						\n\
	subq 	11*4,sp							\n\
	movem	r10,[sp]						\n\
									\n\
        ;; Now we've got this:						\n\
	;; r11 - src							\n\
	;; r13 - dst							\n\
	;; r12 - n							\n\
									\n\
        ;; Update n for the first loop					\n\
        subq    44,r12							\n\
0:									\n\
	movem	[r11+],r10						\n\
        subq   44,r12							\n\
        bge     0b							\n\
	movem	r10,[r13+]						\n\
									\n\
        addq   44,r12  ;; compensate for last loop underflowing n	\n\
									\n\
	;; Restore registers from stack					\n\
        movem [sp+],r10"

     /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n) 
     /* Inputs */ : "0" (dst), "1" (src), "2" (n));
  }

  /* Either we directly starts copying, using dword copying
     in a loop, or we copy as much as possible with 'movem' 
     and then the last block (<44 bytes) is copied here.
     This will work since 'movem' will have updated src,dst,n. */

  while ( n >= 16 )
  {
    *((long*)dst)++ = *((long*)src)++;
    *((long*)dst)++ = *((long*)src)++;
    *((long*)dst)++ = *((long*)src)++;
    *((long*)dst)++ = *((long*)src)++;
    n -= 16;
  }

  /* A switch() is definitely the fastest although it takes a LOT of code.
   * Particularly if you inline code this.
   */
  switch (n)
  {
    case 0:
      break;
    case 1:
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 2:
      *((short*)dst)++ = *((short*)src)++;
      break;
    case 3:
      *((short*)dst)++ = *((short*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 4:
      *((long*)dst)++ = *((long*)src)++;
      break;
    case 5:
      *((long*)dst)++ = *((long*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 6:
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      break;
    case 7:
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 8:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      break;
    case 9:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 10:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      break;
    case 11:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 12:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      break;
    case 13:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
    case 14:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      break;
    case 15:
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((long*)dst)++ = *((long*)src)++;
      *((short*)dst)++ = *((short*)src)++;
      *((char*)dst)++ = *((char*)src)++;
      break;
  }

  return return_dst; /* destination pointer. */
} /* memcpy() */
libc_hidden_def(memcpy)