git.oblomov.eu Git - linux-2.6/blob - arch/cris/arch-v32/lib/memset.c

   1 /*#************************************************************************#*/
   2 /*#-------------------------------------------------------------------------*/
   3 /*#                                                                         */
   4 /*# FUNCTION NAME: memset()                                                 */
   5 /*#                                                                         */
   6 /*# PARAMETERS:  void* dst;   Destination address.                          */
   7 /*#              int     c;   Value of byte to write.                       */
   8 /*#              int   len;   Number of bytes to write.                     */
   9 /*#                                                                         */
  10 /*# RETURNS:     dst.                                                       */
  11 /*#                                                                         */
  12 /*# DESCRIPTION: Sets the memory dst of length len bytes to c, as standard. */
  13 /*#              Framework taken from memcpy.  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 /*# 990713    HP              Tired of watching this function (or           */
  24 /*#                           really, the nonoptimized generic              */
  25 /*#                           implementation) take up 90% of simulator      */
  26 /*#                           output.  Measurements needed.                 */
  27 /*#                                                                         */
  28 /*#-------------------------------------------------------------------------*/
  29
  30 #include <linux/types.h>
  31
  32 /* No, there's no macro saying 12*4, since it is "hard" to get it into
  33    the asm in a good way.  Thus better to expose the problem everywhere.
  34    */
  35
  36 /* Assuming 1 cycle per dword written or read (ok, not really true), and
  37    one per instruction, then 43+3*(n/48-1) <= 24+24*(n/48-1)
  38    so n >= 45.7; n >= 0.9; we win on the first full 48-byte block to set. */
  39
  40 #define ZERO_BLOCK_SIZE (1*12*4)
  41
  42 void *memset(void *pdst,
  43              int c,
  44              size_t plen)
  45 {
  46   /* Ok.  Now we want the parameters put in special registers.
  47      Make sure the compiler is able to make something useful of this. */
  48
  49   register char *return_dst __asm__ ("r10") = pdst;
  50   register int n __asm__ ("r12") = plen;
  51   register int lc __asm__ ("r11") = c;
  52
  53   /* Most apps use memset sanely.  Only those memsetting about 3..4
  54      bytes or less get penalized compared to the generic implementation
  55      - and that's not really sane use. */
  56
  57   /* Ugh.  This is fragile at best.  Check with newer GCC releases, if
  58      they compile cascaded "x |= x << 8" sanely! */
  59   __asm__("movu.b %0,$r13       \n\
  60            lslq 8,$r13          \n\
  61            move.b %0,$r13       \n\
  62            move.d $r13,%0       \n\
  63            lslq 16,$r13         \n\
  64            or.d $r13,%0"
  65           : "=r" (lc) : "0" (lc) : "r13");
  66
  67   {
  68     register char *dst __asm__ ("r13") = pdst;
  69
  70   /* This is NONPORTABLE, but since this whole routine is     */
  71   /* grossly nonportable that doesn't matter.                 */
  72
  73   if (((unsigned long) pdst & 3) != 0
  74      /* Oops! n=0 must be a legal call, regardless of alignment. */
  75       && n >= 3)
  76   {
  77     if ((unsigned long)dst & 1)
  78     {
  79       *dst = (char) lc;
  80       n--;
  81       dst++;
  82     }
  83
  84     if ((unsigned long)dst & 2)
  85     {
  86       *(short *)dst = lc;
  87       n -= 2;
  88       dst += 2;
  89     }
  90   }
  91
  92   /* Now the fun part.  For the threshold value of this, check the equation
  93      above. */
  94   /* Decide which copying method to use. */
  95   if (n >= ZERO_BLOCK_SIZE)
  96   {
  97     /* For large copies we use 'movem' */
  98
  99   /* It is not optimal to tell the compiler about clobbering any
 100      registers; that will move the saving/restoring of those registers
 101      to the function prologue/epilogue, and make non-movem sizes
 102      suboptimal.
 103
 104       This method is not foolproof; it assumes that the "asm reg"
 105      declarations at the beginning of the function really are used
 106      here (beware: they may be moved to temporary registers).
 107       This way, we do not have to save/move the registers around into
 108      temporaries; we can safely use them straight away.
 109
 110       If you want to check that the allocation was right; then
 111       check the equalities in the first comment.  It should say
 112       "r13=r13, r12=r12, r11=r11" */
 113     __asm__ volatile ("                                                 \n\
 114         ;; Check that the register asm declaration got right.           \n\
 115         ;; The GCC manual says it will work, but there *has* been bugs. \n\
 116         .ifnc %0-%1-%4,$r13-$r12-$r11                                   \n\
 117         .err                                                            \n\
 118         .endif                                                          \n\
 119                                                                         \n\
 120         ;; Save the registers we'll clobber in the movem process        \n\
 121         ;; on the stack.  Don't mention them to gcc, it will only be    \n\
 122         ;; upset.                                                       \n\
 123         subq    11*4,$sp                                                \n\
 124         movem   $r10,[$sp]                                              \n\
 125                                                                         \n\
 126         move.d  $r11,$r0                                                \n\
 127         move.d  $r11,$r1                                                \n\
 128         move.d  $r11,$r2                                                \n\
 129         move.d  $r11,$r3                                                \n\
 130         move.d  $r11,$r4                                                \n\
 131         move.d  $r11,$r5                                                \n\
 132         move.d  $r11,$r6                                                \n\
 133         move.d  $r11,$r7                                                \n\
 134         move.d  $r11,$r8                                                \n\
 135         move.d  $r11,$r9                                                \n\
 136         move.d  $r11,$r10                                               \n\
 137                                                                         \n\
 138         ;; Now we've got this:                                          \n\
 139         ;; r13 - dst                                                    \n\
 140         ;; r12 - n                                                      \n\
 141                                                                         \n\
 142         ;; Update n for the first loop                                  \n\
 143         subq    12*4,$r12                                               \n\
 144 0:                                                                      \n\
 145         subq   12*4,$r12                                                \n\
 146         bge     0b                                                      \n\
 147         movem   $r11,[$r13+]                                            \n\
 148                                                                         \n\
 149         addq   12*4,$r12  ;; compensate for last loop underflowing n    \n\
 150                                                                         \n\
 151         ;; Restore registers from stack                                 \n\
 152         movem [$sp+],$r10"
 153
 154      /* Outputs */ : "=r" (dst), "=r" (n)
 155      /* Inputs */ : "0" (dst), "1" (n), "r" (lc));
 156   }
 157
 158     /* Either we directly starts copying, using dword copying
 159        in a loop, or we copy as much as possible with 'movem'
 160        and then the last block (<44 bytes) is copied here.
 161        This will work since 'movem' will have updated src,dst,n. */
 162
 163     while ( n >= 16 )
 164     {
 165       *((long*)dst)++ = lc;
 166       *((long*)dst)++ = lc;
 167       *((long*)dst)++ = lc;
 168       *((long*)dst)++ = lc;
 169       n -= 16;
 170     }
 171
 172     /* A switch() is definitely the fastest although it takes a LOT of code.
 173      * Particularly if you inline code this.
 174      */
 175     switch (n)
 176     {
 177       case 0:
 178         break;
 179       case 1:
 180         *(char*)dst = (char) lc;
 181         break;
 182       case 2:
 183         *(short*)dst = (short) lc;
 184         break;
 185       case 3:
 186         *((short*)dst)++ = (short) lc;
 187         *(char*)dst = (char) lc;
 188         break;
 189       case 4:
 190         *((long*)dst)++ = lc;
 191         break;
 192       case 5:
 193         *((long*)dst)++ = lc;
 194         *(char*)dst = (char) lc;
 195         break;
 196       case 6:
 197         *((long*)dst)++ = lc;
 198         *(short*)dst = (short) lc;
 199         break;
 200       case 7:
 201         *((long*)dst)++ = lc;
 202         *((short*)dst)++ = (short) lc;
 203         *(char*)dst = (char) lc;
 204         break;
 205       case 8:
 206         *((long*)dst)++ = lc;
 207         *((long*)dst)++ = lc;
 208         break;
 209       case 9:
 210         *((long*)dst)++ = lc;
 211         *((long*)dst)++ = lc;
 212         *(char*)dst = (char) lc;
 213         break;
 214       case 10:
 215         *((long*)dst)++ = lc;
 216         *((long*)dst)++ = lc;
 217         *(short*)dst = (short) lc;
 218         break;
 219       case 11:
 220         *((long*)dst)++ = lc;
 221         *((long*)dst)++ = lc;
 222         *((short*)dst)++ = (short) lc;
 223         *(char*)dst = (char) lc;
 224         break;
 225       case 12:
 226         *((long*)dst)++ = lc;
 227         *((long*)dst)++ = lc;
 228         *((long*)dst)++ = lc;
 229         break;
 230       case 13:
 231         *((long*)dst)++ = lc;
 232         *((long*)dst)++ = lc;
 233         *((long*)dst)++ = lc;
 234         *(char*)dst = (char) lc;
 235         break;
 236       case 14:
 237         *((long*)dst)++ = lc;
 238         *((long*)dst)++ = lc;
 239         *((long*)dst)++ = lc;
 240         *(short*)dst = (short) lc;
 241         break;
 242       case 15:
 243         *((long*)dst)++ = lc;
 244         *((long*)dst)++ = lc;
 245         *((long*)dst)++ = lc;
 246         *((short*)dst)++ = (short) lc;
 247         *(char*)dst = (char) lc;
 248         break;
 249     }
 250   }
 251
 252   return return_dst; /* destination pointer. */
 253 } /* memset() */