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         /* FIXME this part needs more test */
  69         /* Do a descending copy - this is a bit trickier! */
  70         dst += c;
  71         src += c;
  72
  73         if (c >= 4) {
  74                 unsigned  value, buf_hold;
  75
  76                 /* Align the destination to a word boundry. */
  77                 /* This is done in an endian independant manner. */
  78
  79                 switch ((unsigned long)dst & 3) {
  80                 case 3:
  81                         *--dst = *--src;
  82                         --c;
  83                 case 2:
  84                         *--dst = *--src;
  85                         --c;
  86                 case 1:
  87                         *--dst = *--src;
  88                         --c;
  89                 }
  90
  91                 i_dst = (void *)dst;
  92                 /* Choose a copy scheme based on the source */
  93                 /* alignment relative to dstination. */
  94                 switch ((unsigned long)src & 3) {
  95                 case 0x0:       /* Both byte offsets are aligned */
  96
  97                         i_src  = (const void *)src;
  98
  99                         for (; c >= 4; c -= 4)
 100                                 *--i_dst = *--i_src;
 101
 102                         src  = (const void *)i_src;
 103                         break;
 104                 case 0x1:       /* Unaligned - Off by 1 */
 105                         /* Word align the source */
 106                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 107
 108                         /* Load the holding buffer */
 109                         buf_hold = *--i_src >> 24;
 110
 111                         for (; c >= 4; c -= 4) {
 112                                 value = *--i_src;
 113                                 *--i_dst = buf_hold << 8 | value;
 114                                 buf_hold = value >> 24;
 115                         }
 116
 117                         /* Realign the source */
 118                         src = (const void *)i_src;
 119                         src += 1;
 120                         break;
 121                 case 0x2:       /* Unaligned - Off by 2 */
 122                         /* Word align the source */
 123                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 124
 125                         /* Load the holding buffer */
 126                         buf_hold = *--i_src >> 16;
 127
 128                         for (; c >= 4; c -= 4) {
 129                                 value = *--i_src;
 130                                 *--i_dst = buf_hold << 16 | value;
 131                                 buf_hold = value >> 16;
 132                         }
 133
 134                         /* Realign the source */
 135                         src = (const void *)i_src;
 136                         src += 2;
 137                         break;
 138                 case 0x3:       /* Unaligned - Off by 3 */
 139                         /* Word align the source */
 140                         i_src = (const void *) (((unsigned)src + 4) & ~3);
 141
 142                         /* Load the holding buffer */
 143                         buf_hold = *--i_src >> 8;
 144
 145                         for (; c >= 4; c -= 4) {
 146                                 value = *--i_src;
 147                                 *--i_dst = buf_hold << 24 | value;
 148                                 buf_hold = value >> 8;
 149                         }
 150
 151                         /* Realign the source */
 152                         src = (const void *)i_src;
 153                         src += 3;
 154                         break;
 155                 }
 156                 dst = (void *)i_dst;
 157         }
 158
 159         /* simple fast copy, ... unless a cache boundry is crossed */
 160         /* Finish off any remaining bytes */
 161         switch (c) {
 162         case 4:
 163                 *--dst = *--src;
 164         case 3:
 165                 *--dst = *--src;
 166         case 2:
 167                 *--dst = *--src;
 168         case 1:
 169                 *--dst = *--src;
 170         }
 171         return v_dst;
 172 #endif
 173 }
 174 EXPORT_SYMBOL(memmove);
 175 #endif /* __HAVE_ARCH_MEMMOVE */