git.oblomov.eu Git - linux-2.6/blob - arch/cris/arch-v10/lib/string.c

   1 /*#************************************************************************#*/
   2 /*#-------------------------------------------------------------------------*/
   3 /*#                                                                         */
   4 /*# FUNCTION NAME: memcpy()                                                 */
   5 /*#                                                                         */
   6 /*# PARAMETERS:  void* dst;   Destination address.                          */
   7 /*#              void* src;   Source address.                               */
   8 /*#              int   len;   Number of bytes to copy.                      */
   9 /*#                                                                         */
  10 /*# RETURNS:     dst.                                                       */
  11 /*#                                                                         */
  12 /*# DESCRIPTION: Copies len bytes of memory from src to dst.  No guarantees */
  13 /*#              about copying of overlapping memory areas. This routine is */
  14 /*#              very sensitive to compiler changes in register allocation. */
  15 /*#              Should really be rewritten to avoid this problem.          */
  16 /*#                                                                         */
  17 /*#-------------------------------------------------------------------------*/
  18 /*#                                                                         */
  19 /*# HISTORY                                                                 */
  20 /*#                                                                         */
  21 /*# DATE      NAME            CHANGES                                       */
  22 /*# ----      ----            -------                                       */
  23 /*# 941007    Kenny R         Creation                                      */
  24 /*# 941011    Kenny R         Lots of optimizations and inlining.           */
  25 /*# 941129    Ulf A           Adapted for use in libc.                      */
  26 /*# 950216    HP              N==0 forgotten if non-aligned src/dst.        */
  27 /*#                           Added some optimizations.                     */
  28 /*# 001025    HP              Make src and dst char *.  Align dst to        */
  29 /*#                           dword, not just word-if-both-src-and-dst-     */
  30 /*#                           are-misaligned.                               */
  31 /*#                                                                         */
  32 /*#-------------------------------------------------------------------------*/
  33
  34 #include <linux/types.h>
  35
  36 void *memcpy(void *pdst,
  37              const void *psrc,
  38              size_t pn)
  39 {
  40   /* Ok.  Now we want the parameters put in special registers.
  41      Make sure the compiler is able to make something useful of this.
  42       As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
  43
  44      If gcc was alright, it really would need no temporaries, and no
  45      stack space to save stuff on. */
  46
  47   register void *return_dst __asm__ ("r10") = pdst;
  48   register char *dst __asm__ ("r13") = pdst;
  49   register const char *src __asm__ ("r11") = psrc;
  50   register int n __asm__ ("r12") = pn;
  51
  52
  53   /* When src is aligned but not dst, this makes a few extra needless
  54      cycles.  I believe it would take as many to check that the
  55      re-alignment was unnecessary.  */
  56   if (((unsigned long) dst & 3) != 0
  57       /* Don't align if we wouldn't copy more than a few bytes; so we
  58          don't have to check further for overflows.  */
  59       && n >= 3)
  60   {
  61     if ((unsigned long) dst & 1)
  62     {
  63       n--;
  64       *(char*)dst = *(char*)src;
  65       src++;
  66       dst++;
  67     }
  68
  69     if ((unsigned long) dst & 2)
  70     {
  71       n -= 2;
  72       *(short*)dst = *(short*)src;
  73       src += 2;
  74       dst += 2;
  75     }
  76   }
  77
  78   /* Decide which copying method to use. */
  79   if (n >= 44*2)                /* Break even between movem and
  80                                    move16 is at 38.7*2, but modulo 44. */
  81   {
  82     /* For large copies we use 'movem' */
  83
  84   /* It is not optimal to tell the compiler about clobbering any
  85      registers; that will move the saving/restoring of those registers
  86      to the function prologue/epilogue, and make non-movem sizes
  87      suboptimal.
  88
  89       This method is not foolproof; it assumes that the "asm reg"
  90      declarations at the beginning of the function really are used
  91      here (beware: they may be moved to temporary registers).
  92       This way, we do not have to save/move the registers around into
  93      temporaries; we can safely use them straight away.
  94
  95       If you want to check that the allocation was right; then
  96       check the equalities in the first comment.  It should say
  97       "r13=r13, r11=r11, r12=r12" */
  98     __asm__ volatile ("\n\
  99         ;; Check that the following is true (same register names on     \n\
 100         ;; both sides of equal sign, as in r8=r8):                      \n\
 101         ;; %0=r13, %1=r11, %2=r12                                       \n\
 102         ;;                                                              \n\
 103         ;; Save the registers we'll use in the movem process            \n\
 104         ;; on the stack.                                                \n\
 105         subq    11*4,$sp                                                \n\
 106         movem   $r10,[$sp]                                              \n\
 107                                                                         \n\
 108         ;; Now we've got this:                                          \n\
 109         ;; r11 - src                                                    \n\
 110         ;; r13 - dst                                                    \n\
 111         ;; r12 - n                                                      \n\
 112                                                                         \n\
 113         ;; Update n for the first loop                                  \n\
 114         subq    44,$r12                                                 \n\
 115 0:                                                                      \n\
 116         movem   [$r11+],$r10                                            \n\
 117         subq    44,$r12                                                 \n\
 118         bge     0b                                                      \n\
 119         movem   $r10,[$r13+]                                            \n\
 120                                                                         \n\
 121         addq    44,$r12 ;; compensate for last loop underflowing n      \n\
 122                                                                         \n\
 123         ;; Restore registers from stack                                 \n\
 124         movem   [$sp+],$r10"
 125
 126      /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n)
 127      /* Inputs */ : "0" (dst), "1" (src), "2" (n));
 128
 129   }
 130
 131   /* Either we directly starts copying, using dword copying
 132      in a loop, or we copy as much as possible with 'movem'
 133      and then the last block (<44 bytes) is copied here.
 134      This will work since 'movem' will have updated src,dst,n. */
 135
 136   while ( n >= 16 )
 137   {
 138     *((long*)dst)++ = *((long*)src)++;
 139     *((long*)dst)++ = *((long*)src)++;
 140     *((long*)dst)++ = *((long*)src)++;
 141     *((long*)dst)++ = *((long*)src)++;
 142     n -= 16;
 143   }
 144
 145   /* A switch() is definitely the fastest although it takes a LOT of code.
 146    * Particularly if you inline code this.
 147    */
 148   switch (n)
 149   {
 150     case 0:
 151       break;
 152     case 1:
 153       *(char*)dst = *(char*)src;
 154       break;
 155     case 2:
 156       *(short*)dst = *(short*)src;
 157       break;
 158     case 3:
 159       *((short*)dst)++ = *((short*)src)++;
 160       *(char*)dst = *(char*)src;
 161       break;
 162     case 4:
 163       *((long*)dst)++ = *((long*)src)++;
 164       break;
 165     case 5:
 166       *((long*)dst)++ = *((long*)src)++;
 167       *(char*)dst = *(char*)src;
 168       break;
 169     case 6:
 170       *((long*)dst)++ = *((long*)src)++;
 171       *(short*)dst = *(short*)src;
 172       break;
 173     case 7:
 174       *((long*)dst)++ = *((long*)src)++;
 175       *((short*)dst)++ = *((short*)src)++;
 176       *(char*)dst = *(char*)src;
 177       break;
 178     case 8:
 179       *((long*)dst)++ = *((long*)src)++;
 180       *((long*)dst)++ = *((long*)src)++;
 181       break;
 182     case 9:
 183       *((long*)dst)++ = *((long*)src)++;
 184       *((long*)dst)++ = *((long*)src)++;
 185       *(char*)dst = *(char*)src;
 186       break;
 187     case 10:
 188       *((long*)dst)++ = *((long*)src)++;
 189       *((long*)dst)++ = *((long*)src)++;
 190       *(short*)dst = *(short*)src;
 191       break;
 192     case 11:
 193       *((long*)dst)++ = *((long*)src)++;
 194       *((long*)dst)++ = *((long*)src)++;
 195       *((short*)dst)++ = *((short*)src)++;
 196       *(char*)dst = *(char*)src;
 197       break;
 198     case 12:
 199       *((long*)dst)++ = *((long*)src)++;
 200       *((long*)dst)++ = *((long*)src)++;
 201       *((long*)dst)++ = *((long*)src)++;
 202       break;
 203     case 13:
 204       *((long*)dst)++ = *((long*)src)++;
 205       *((long*)dst)++ = *((long*)src)++;
 206       *((long*)dst)++ = *((long*)src)++;
 207       *(char*)dst = *(char*)src;
 208       break;
 209     case 14:
 210       *((long*)dst)++ = *((long*)src)++;
 211       *((long*)dst)++ = *((long*)src)++;
 212       *((long*)dst)++ = *((long*)src)++;
 213       *(short*)dst = *(short*)src;
 214       break;
 215     case 15:
 216       *((long*)dst)++ = *((long*)src)++;
 217       *((long*)dst)++ = *((long*)src)++;
 218       *((long*)dst)++ = *((long*)src)++;
 219       *((short*)dst)++ = *((short*)src)++;
 220       *(char*)dst = *(char*)src;
 221       break;
 222   }
 223
 224   return return_dst; /* destination pointer. */
 225 } /* memcpy() */