arch/cris/arch-v10/lib/string.c

   1 /* A memcpy for CRIS.
   2    Copyright (C) 1994-2005 Axis Communications.
   3    All rights reserved.
   4
   5    Redistribution and use in source and binary forms, with or without
   6    modification, are permitted provided that the following conditions
   7    are met:
   8
   9    1. Redistributions of source code must retain the above copyright
  10       notice, this list of conditions and the following disclaimer.
  11
  12    2. Neither the name of Axis Communications nor the names of its
  13       contributors may be used to endorse or promote products derived
  14       from this software without specific prior written permission.
  15
  16    THIS SOFTWARE IS PROVIDED BY AXIS COMMUNICATIONS AND ITS CONTRIBUTORS
  17    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL AXIS
  20    COMMUNICATIONS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  21    INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  23    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24    HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  25    STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  26    IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  27    POSSIBILITY OF SUCH DAMAGE.  */
  28
  29 /* FIXME: This file should really only be used for reference, as the
  30    result is somewhat depending on gcc generating what we expect rather
  31    than what we describe.  An assembly file should be used instead.  */
  32
  33 #include <stddef.h>
  34
  35 /* Break even between movem and move16 is really at 38.7 * 2, but
  36    modulo 44, so up to the next multiple of 44, we use ordinary code.  */
  37 #define MEMCPY_BY_BLOCK_THRESHOLD (44 * 2)
  38
  39 /* No name ambiguities in this file.  */
  40 __asm__ (".syntax no_register_prefix");
  41
  42 void *
  43 memcpy(void *pdst, const void *psrc, size_t pn)
  44 {
  45   /* Now we want the parameters put in special registers.
  46      Make sure the compiler is able to make something useful of this.
  47      As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
  48
  49      If gcc was allright, it really would need no temporaries, and no
  50      stack space to save stuff on.  */
  51
  52   register void *return_dst __asm__ ("r10") = pdst;
  53   register unsigned char *dst __asm__ ("r13") = pdst;
  54   register unsigned const char *src __asm__ ("r11") = psrc;
  55   register int n __asm__ ("r12") = pn;
  56
  57   /* When src is aligned but not dst, this makes a few extra needless
  58      cycles.  I believe it would take as many to check that the
  59      re-alignment was unnecessary.  */
  60   if (((unsigned long) dst & 3) != 0
  61       /* Don't align if we wouldn't copy more than a few bytes; so we
  62          don't have to check further for overflows.  */
  63       && n >= 3)
  64   {
  65     if ((unsigned long) dst & 1)
  66       {
  67         n--;
  68         *dst = *src;
  69         src++;
  70         dst++;
  71       }
  72
  73     if ((unsigned long) dst & 2)
  74       {
  75         n -= 2;
  76         *(short *) dst = *(short *) src;
  77         src += 2;
  78         dst += 2;
  79       }
  80   }
  81
  82   /* Decide which copying method to use.  */
  83   if (n >= MEMCPY_BY_BLOCK_THRESHOLD)
  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
  90         ("\
  91          ;; GCC does promise correct register allocations, but let's    \n\
  92          ;; make sure it keeps its promises.                            \n\
  93          .ifnc %0-%1-%2,$r13-$r11-$r12                                  \n\
  94          .error \"GCC reg alloc bug: %0-%1-%4 != $r13-$r12-$r11\"       \n\
  95          .endif                                                         \n\
  96                                                                         \n\
  97          ;; Save the registers we'll use in the movem process           \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 "
 111 #ifdef __arch_common_v10_v32
 112          /* Cater to branch offset difference between v32 and v10.  We
 113             assume the branch below has an 8-bit offset.  */
 114 "        setf\n"
 115 #endif
 116 "        movem  [r11+],r10                                              \n\
 117          subq   44,r12                                                  \n\
 118          bge     0b                                                     \n\
 119          movem  r10,[r13+]                                              \n\
 120                                                                         \n\
 121          ;; Compensate for last loop underflowing n.                    \n\
 122          addq   44,r12                                                  \n\
 123                                                                         \n\
 124          ;; Restore registers from stack.                               \n\
 125          movem [sp+],r10"
 126
 127          /* Outputs.  */
 128          : "=r" (dst), "=r" (src), "=r" (n)
 129
 130          /* Inputs.  */
 131          : "0" (dst), "1" (src), "2" (n));
 132     }
 133
 134   while (n >= 16)
 135     {
 136       *(long *) dst = *(long *) src; dst += 4; src += 4;
 137       *(long *) dst = *(long *) src; dst += 4; src += 4;
 138       *(long *) dst = *(long *) src; dst += 4; src += 4;
 139       *(long *) dst = *(long *) src; dst += 4; src += 4;
 140
 141       n -= 16;
 142     }
 143
 144   switch (n)
 145     {
 146     case 0:
 147       break;
 148
 149     case 1:
 150       *dst = *src;
 151       break;
 152
 153     case 2:
 154       *(short *) dst = *(short *) src;
 155       break;
 156
 157     case 3:
 158       *(short *) dst = *(short *) src; dst += 2; src += 2;
 159       *dst = *src;
 160       break;
 161
 162     case 4:
 163       *(long *) dst = *(long *) src;
 164       break;
 165
 166     case 5:
 167       *(long *) dst = *(long *) src; dst += 4; src += 4;
 168       *dst = *src;
 169       break;
 170
 171     case 6:
 172       *(long *) dst = *(long *) src; dst += 4; src += 4;
 173       *(short *) dst = *(short *) src;
 174       break;
 175
 176     case 7:
 177       *(long *) dst = *(long *) src; dst += 4; src += 4;
 178       *(short *) dst = *(short *) src; dst += 2; src += 2;
 179       *dst = *src;
 180       break;
 181
 182     case 8:
 183       *(long *) dst = *(long *) src; dst += 4; src += 4;
 184       *(long *) dst = *(long *) src;
 185       break;
 186
 187     case 9:
 188       *(long *) dst = *(long *) src; dst += 4; src += 4;
 189       *(long *) dst = *(long *) src; dst += 4; src += 4;
 190       *dst = *src;
 191       break;
 192
 193     case 10:
 194       *(long *) dst = *(long *) src; dst += 4; src += 4;
 195       *(long *) dst = *(long *) src; dst += 4; src += 4;
 196       *(short *) dst = *(short *) src;
 197       break;
 198
 199     case 11:
 200       *(long *) dst = *(long *) src; dst += 4; src += 4;
 201       *(long *) dst = *(long *) src; dst += 4; src += 4;
 202       *(short *) dst = *(short *) src; dst += 2; src += 2;
 203       *dst = *src;
 204       break;
 205
 206     case 12:
 207       *(long *) dst = *(long *) src; dst += 4; src += 4;
 208       *(long *) dst = *(long *) src; dst += 4; src += 4;
 209       *(long *) dst = *(long *) src;
 210       break;
 211
 212     case 13:
 213       *(long *) dst = *(long *) src; dst += 4; src += 4;
 214       *(long *) dst = *(long *) src; dst += 4; src += 4;
 215       *(long *) dst = *(long *) src; dst += 4; src += 4;
 216       *dst = *src;
 217       break;
 218
 219     case 14:
 220       *(long *) dst = *(long *) src; dst += 4; src += 4;
 221       *(long *) dst = *(long *) src; dst += 4; src += 4;
 222       *(long *) dst = *(long *) src; dst += 4; src += 4;
 223       *(short *) dst = *(short *) src;
 224       break;
 225
 226     case 15:
 227       *(long *) dst = *(long *) src; dst += 4; src += 4;
 228       *(long *) dst = *(long *) src; dst += 4; src += 4;
 229       *(long *) dst = *(long *) src; dst += 4; src += 4;
 230       *(short *) dst = *(short *) src; dst += 2; src += 2;
 231       *dst = *src;
 232       break;
 233     }
 234
 235   return return_dst;
 236 }