git.oblomov.eu Git - linux-2.6/blob - arch/cris/arch-v32/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 allright, 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.  Movem is dirt cheap, so the
  79      overheap is low enough to always use the minimum block size as the
  80      threshold.  */
  81   if (n >= 44)
  82   {
  83     /* For large copies we use 'movem' */
  84
  85   /* It is not optimal to tell the compiler about clobbering any
  86      registers; that will move the saving/restoring of those registers
  87      to the function prologue/epilogue, and make non-movem sizes
  88      suboptimal.  */
  89     __asm__ volatile ("                                                 \n\
  90         ;; Check that the register asm declaration got right.           \n\
  91         ;; The GCC manual explicitly says TRT will happen.              \n\
  92         .ifnc %0-%1-%2,$r13-$r11-$r12                                   \n\
  93         .err                                                            \n\
  94         .endif                                                          \n\
  95                                                                         \n\
  96         ;; Save the registers we'll use in the movem process            \n\
  97                                                                         \n\
  98         ;; on the stack.                                                \n\
  99         subq    11*4,$sp                                                \n\
 100         movem   $r10,[$sp]                                              \n\
 101                                                                         \n\
 102         ;; Now we've got this:                                          \n\
 103         ;; r11 - src                                                    \n\
 104         ;; r13 - dst                                                    \n\
 105         ;; r12 - n                                                      \n\
 106                                                                         \n\
 107         ;; Update n for the first loop                                  \n\
 108         subq    44,$r12                                                 \n\
 109 0:                                                                      \n\
 110         movem   [$r11+],$r10                                            \n\
 111         subq   44,$r12                                                  \n\
 112         bge     0b                                                      \n\
 113         movem   $r10,[$r13+]                                            \n\
 114                                                                         \n\
 115         addq   44,$r12  ;; compensate for last loop underflowing n      \n\
 116                                                                         \n\
 117         ;; Restore registers from stack                                 \n\
 118         movem [$sp+],$r10"
 119
 120      /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n)
 121      /* Inputs */ : "0" (dst), "1" (src), "2" (n));
 122
 123   }
 124
 125   /* Either we directly starts copying, using dword copying
 126      in a loop, or we copy as much as possible with 'movem'
 127      and then the last block (<44 bytes) is copied here.
 128      This will work since 'movem' will have updated src,dst,n. */
 129
 130   while ( n >= 16 )
 131   {
 132     *((long*)dst)++ = *((long*)src)++;
 133     *((long*)dst)++ = *((long*)src)++;
 134     *((long*)dst)++ = *((long*)src)++;
 135     *((long*)dst)++ = *((long*)src)++;
 136     n -= 16;
 137   }
 138
 139   /* A switch() is definitely the fastest although it takes a LOT of code.
 140    * Particularly if you inline code this.
 141    */
 142   switch (n)
 143   {
 144     case 0:
 145       break;
 146     case 1:
 147       *(char*)dst = *(char*)src;
 148       break;
 149     case 2:
 150       *(short*)dst = *(short*)src;
 151       break;
 152     case 3:
 153       *((short*)dst)++ = *((short*)src)++;
 154       *(char*)dst = *(char*)src;
 155       break;
 156     case 4:
 157       *((long*)dst)++ = *((long*)src)++;
 158       break;
 159     case 5:
 160       *((long*)dst)++ = *((long*)src)++;
 161       *(char*)dst = *(char*)src;
 162       break;
 163     case 6:
 164       *((long*)dst)++ = *((long*)src)++;
 165       *(short*)dst = *(short*)src;
 166       break;
 167     case 7:
 168       *((long*)dst)++ = *((long*)src)++;
 169       *((short*)dst)++ = *((short*)src)++;
 170       *(char*)dst = *(char*)src;
 171       break;
 172     case 8:
 173       *((long*)dst)++ = *((long*)src)++;
 174       *((long*)dst)++ = *((long*)src)++;
 175       break;
 176     case 9:
 177       *((long*)dst)++ = *((long*)src)++;
 178       *((long*)dst)++ = *((long*)src)++;
 179       *(char*)dst = *(char*)src;
 180       break;
 181     case 10:
 182       *((long*)dst)++ = *((long*)src)++;
 183       *((long*)dst)++ = *((long*)src)++;
 184       *(short*)dst = *(short*)src;
 185       break;
 186     case 11:
 187       *((long*)dst)++ = *((long*)src)++;
 188       *((long*)dst)++ = *((long*)src)++;
 189       *((short*)dst)++ = *((short*)src)++;
 190       *(char*)dst = *(char*)src;
 191       break;
 192     case 12:
 193       *((long*)dst)++ = *((long*)src)++;
 194       *((long*)dst)++ = *((long*)src)++;
 195       *((long*)dst)++ = *((long*)src)++;
 196       break;
 197     case 13:
 198       *((long*)dst)++ = *((long*)src)++;
 199       *((long*)dst)++ = *((long*)src)++;
 200       *((long*)dst)++ = *((long*)src)++;
 201       *(char*)dst = *(char*)src;
 202       break;
 203     case 14:
 204       *((long*)dst)++ = *((long*)src)++;
 205       *((long*)dst)++ = *((long*)src)++;
 206       *((long*)dst)++ = *((long*)src)++;
 207       *(short*)dst = *(short*)src;
 208       break;
 209     case 15:
 210       *((long*)dst)++ = *((long*)src)++;
 211       *((long*)dst)++ = *((long*)src)++;
 212       *((long*)dst)++ = *((long*)src)++;
 213       *((short*)dst)++ = *((short*)src)++;
 214       *(char*)dst = *(char*)src;
 215       break;
 216   }
 217
 218   return return_dst; /* destination pointer. */
 219 } /* memcpy() */