release/src-rt-6.x.4708/linux/linux-2.6.36/arch/microblaze/lib/memmove.c

   1 /*
   2  * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
   3  * Copyright (C) 2008-2009 PetaLogix
   4  * Copyright (C) 2007 John Williams
   5  *
   6  * Reasonably optimised generic C-code for memcpy on Microblaze
   7  * This is generic C code to do efficient, alignment-aware memmove.
   8  *
   9  * It is based on demo code originally Copyright 2001 by Intel Corp, taken from
  10  * http://www.embedded.com/showArticle.jhtml?articleID=19205567
  11  *
  12  * Attempts were made, unsuccessfully, to contact the original
  13  * author of this code (Michael Morrow, Intel).  Below is the original
  14  * copyright notice.
  15  *
  16  * This software has been developed by Intel Corporation.
  17  * Intel specifically disclaims all warranties, express or
  18  * implied, and all liability, including consequential and
  19  * other indirect damages, for the use of this program, including
  20  * liability for infringement of any proprietary rights,
  21  * and including the warranties of merchantability and fitness
  22  * for a particular purpose. Intel does not assume any
  23  * responsibility for and errors which may appear in this program
  24  * not any responsibility to update it.
  25  */
  26
  27 #include <linux/types.h>
  28 #include <linux/stddef.h>
  29 #include <linux/compiler.h>
  30 #include <linux/module.h>
  31 #include <linux/string.h>
  32
  33 #ifdef __HAVE_ARCH_MEMMOVE
  34 void *memmove(void *v_dst, const void *v_src, __kernel_size_t c)
  35 {
  36         const char *src = v_src;
  37         char *dst = v_dst;
  38
  39 #ifdef CONFIG_OPT_LIB_FUNCTION
  40         const uint32_t *i_src;
  41         uint32_t *i_dst;
  42 #endif
  43
  44         if (!c)
  45                 return v_dst;
  46
  47         /* Use memcpy when source is higher than dest */
  48         if (v_dst <= v_src)
  49                 return memcpy(v_dst, v_src, c);
  50
  51 #ifndef CONFIG_OPT_LIB_FUNCTION
  52         /* copy backwards, from end to beginning */
  53         src += c;
  54         dst += c;
  55
  56         /* Simple, byte oriented memmove. */
  57         while (c--)
  58                 *--dst = *--src;
  59
  60         return v_dst;
  61 #else
  62         /* The following code tries to optimize the copy by using unsigned
  63          * alignment. This will work fine if both source and destination are
  64          * aligned on the same boundary. However, if they are aligned on
  65          * different boundaries shifts will be necessary. This might result in
  66          * bad performance on MicroBlaze systems without a barrel shifter.
  67          */
  68         /* Do a descending copy - this is a bit trickier! */
  69         dst += c;
  70         src += c;
  71
  72         if (c >= 4) {
  73                 unsigned  value, buf_hold;
  74
  75                 /* Align the destination to a word boundry. */
  76                 /* This is done in an endian independant manner. */
  77
  78                 switch ((unsigned long)dst & 3) {
  79                 case 3:
  80                         *--dst = *--src;
  81                         --c;
  82                 case 2:
  83                         *--dst = *--src;
  84                         --c;
  85                 case 1:
  86                         *--dst = *--src;
  87                         --c;
  88                 }
  89
  90                 i_dst = (void *)dst;
  91                 /* Choose a copy scheme based on the source */
  92                 /* alignment relative to dstination. */
  93                 switch ((unsigned long)src & 3) {
  94                 case 0x0:       /* Both byte offsets are aligned */
  95
  96                         i_src  = (const void *)src;
  97
  98                         for (; c >= 4; c -= 4)
  99                                 *--i_dst = *--i_src;
 100
 101                         src  = (const void *)i_src;
 102                         break;
 103                 case 0x1:       /* Unaligned - Off by 1 */
 104                         /* Word align the source */
 105                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 106
 107                         /* Load the holding buffer */
 108                         buf_hold = *--i_src >> 24;
 109
 110                         for (; c >= 4; c -= 4) {
 111                                 value = *--i_src;
 112                                 *--i_dst = buf_hold << 8 | value;
 113                                 buf_hold = value >> 24;
 114                         }
 115
 116                         /* Realign the source */
 117                         src = (const void *)i_src;
 118                         src += 1;
 119                         break;
 120                 case 0x2:       /* Unaligned - Off by 2 */
 121                         /* Word align the source */
 122                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 123
 124                         /* Load the holding buffer */
 125                         buf_hold = *--i_src >> 16;
 126
 127                         for (; c >= 4; c -= 4) {
 128                                 value = *--i_src;
 129                                 *--i_dst = buf_hold << 16 | value;
 130                                 buf_hold = value >> 16;
 131                         }
 132
 133                         /* Realign the source */
 134                         src = (const void *)i_src;
 135                         src += 2;
 136                         break;
 137                 case 0x3:       /* Unaligned - Off by 3 */
 138                         /* Word align the source */
 139                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 140
 141                         /* Load the holding buffer */
 142                         buf_hold = *--i_src >> 8;
 143
 144                         for (; c >= 4; c -= 4) {
 145                                 value = *--i_src;
 146                                 *--i_dst = buf_hold << 24 | value;
 147                                 buf_hold = value >> 8;
 148                         }
 149
 150                         /* Realign the source */
 151                         src = (const void *)i_src;
 152                         src += 3;
 153                         break;
 154                 }
 155                 dst = (void *)i_dst;
 156         }
 157
 158         /* simple fast copy, ... unless a cache boundry is crossed */
 159         /* Finish off any remaining bytes */
 160         switch (c) {
 161         case 4:
 162                 *--dst = *--src;
 163         case 3:
 164                 *--dst = *--src;
 165         case 2:
 166                 *--dst = *--src;
 167         case 1:
 168                 *--dst = *--src;
 169         }
 170         return v_dst;
 171 #endif
 172 }
 173 EXPORT_SYMBOL(memmove);
 174 #endif /* __HAVE_ARCH_MEMMOVE */