arch/tile/lib/memmove.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/types.h>
  16 #include <linux/string.h>
  17 #include <linux/module.h>
  18
  19 void *memmove(void *dest, const void *src, size_t n)
  20 {
  21         if ((const char *)src >= (char *)dest + n
  22             || (char *)dest >= (const char *)src + n) {
  23                 /* We found no overlap, so let memcpy do all the heavy
  24                  * lifting (prefetching, etc.)
  25                  */
  26                 return memcpy(dest, src, n);
  27         }
  28
  29         if (n != 0) {
  30                 const uint8_t *in;
  31                 uint8_t x;
  32                 uint8_t *out;
  33                 int stride;
  34
  35                 if (src < dest) {
  36                         /* copy backwards */
  37                         in = (const uint8_t *)src + n - 1;
  38                         out = (uint8_t *)dest + n - 1;
  39                         stride = -1;
  40                 } else {
  41                         /* copy forwards */
  42                         in = (const uint8_t *)src;
  43                         out = (uint8_t *)dest;
  44                         stride = 1;
  45                 }
  46
  47                 /* Manually software-pipeline this loop. */
  48                 x = *in;
  49                 in += stride;
  50
  51                 while (--n != 0) {
  52                         *out = x;
  53                         out += stride;
  54                         x = *in;
  55                         in += stride;
  56                 }
  57
  58                 *out = x;
  59         }
  60
  61         return dest;
  62 }
  63 EXPORT_SYMBOL(memmove);