gas/config/atof-tahoe.c

   1 /* atof_tahoe.c - turn a string into a Tahoe floating point number
   2    Copyright 1987, 1993, 2000 Free Software Foundation, Inc.
   3
   4 /* This is really a simplified version of atof_vax.c. I glommed it wholesale
   5    and then shaved it down. I don't even know how it works. (Don't you find
   6    my honesty refreshing?  Devon E Bowen <bowen@cs.buffalo.edu>
   7
   8    I don't allow uppercase letters in the precision descriptors.
   9    i.e. 'f' and 'd' are allowed but 'F' and 'D' aren't.  */
  10
  11 #include "as.h"
  12
  13 /* Precision in LittleNums.  */
  14 #define MAX_PRECISION (4)
  15 #define D_PRECISION (4)
  16 #define F_PRECISION (2)
  17
  18 /* Precision in chars.  */
  19 #define D_PRECISION_CHARS (8)
  20 #define F_PRECISION_CHARS (4)
  21
  22 /* Length in LittleNums of guard bits.  */
  23 #define GUARD (2)
  24
  25 static const long int mask[] =
  26 {
  27   0x00000000,
  28   0x00000001,
  29   0x00000003,
  30   0x00000007,
  31   0x0000000f,
  32   0x0000001f,
  33   0x0000003f,
  34   0x0000007f,
  35   0x000000ff,
  36   0x000001ff,
  37   0x000003ff,
  38   0x000007ff,
  39   0x00000fff,
  40   0x00001fff,
  41   0x00003fff,
  42   0x00007fff,
  43   0x0000ffff,
  44   0x0001ffff,
  45   0x0003ffff,
  46   0x0007ffff,
  47   0x000fffff,
  48   0x001fffff,
  49   0x003fffff,
  50   0x007fffff,
  51   0x00ffffff,
  52   0x01ffffff,
  53   0x03ffffff,
  54   0x07ffffff,
  55   0x0fffffff,
  56   0x1fffffff,
  57   0x3fffffff,
  58   0x7fffffff,
  59   0xffffffff
  60 };
  61 \f
  62 /* Shared between flonum_gen2tahoe and next_bits.  */
  63 static int bits_left_in_littlenum;
  64 static LITTLENUM_TYPE *littlenum_pointer;
  65 static LITTLENUM_TYPE *littlenum_end;
  66
  67 #if __STDC__ == 1
  68
  69 int flonum_gen2tahoe (int format_letter, FLONUM_TYPE * f,
  70                       LITTLENUM_TYPE * words);
  71
  72 #else /* not __STDC__  */
  73
  74 int flonum_gen2tahoe ();
  75
  76 #endif /* not __STDC__  */
  77
  78 static int
  79 next_bits (number_of_bits)
  80      int number_of_bits;
  81 {
  82   int return_value;
  83
  84   if (littlenum_pointer < littlenum_end)
  85     return 0;
  86   if (number_of_bits >= bits_left_in_littlenum)
  87     {
  88       return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
  89       number_of_bits -= bits_left_in_littlenum;
  90       return_value <<= number_of_bits;
  91       bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
  92       littlenum_pointer--;
  93       if (littlenum_pointer >= littlenum_end)
  94         return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) &
  95           mask[number_of_bits];
  96     }
  97   else
  98     {
  99       bits_left_in_littlenum -= number_of_bits;
 100       return_value = mask[number_of_bits] &
 101         ((*littlenum_pointer) >> bits_left_in_littlenum);
 102     }
 103   return return_value;
 104 }
 105
 106 static void
 107 make_invalid_floating_point_number (words)
 108      LITTLENUM_TYPE *words;
 109 {
 110   /* Floating Reserved Operand Code.  */
 111   *words = 0x8000;
 112 }
 113 \f
 114 static int                      /* 0 means letter is OK.  */
 115 what_kind_of_float (letter, precisionP, exponent_bitsP)
 116      /* In: lowercase please. What kind of float?  */
 117      char letter;
 118
 119      /* Number of 16-bit words in the float.  */
 120      int *precisionP;
 121
 122      /* Number of exponent bits.  */
 123      long int *exponent_bitsP;
 124 {
 125   int retval;                   /* 0: OK.  */
 126
 127   retval = 0;
 128   switch (letter)
 129     {
 130     case 'f':
 131       *precisionP = F_PRECISION;
 132       *exponent_bitsP = 8;
 133       break;
 134
 135     case 'd':
 136       *precisionP = D_PRECISION;
 137       *exponent_bitsP = 8;
 138       break;
 139
 140     default:
 141       retval = 69;
 142       break;
 143     }
 144   return (retval);
 145 }
 146 \f
 147 /* Warning: This returns 16-bit LITTLENUMs, because that is what the
 148    VAX thinks in.  It is up to the caller to figure out any alignment
 149    problems and to conspire for the bytes/word to be emitted in the
 150    right order. Bigendians beware!  */
 151
 152 char *                          /* Return pointer past text consumed.  */
 153 atof_tahoe (str, what_kind, words)
 154      char *str;                 /* Text to convert to binary.  */
 155      char what_kind;            /* 'd', 'f', 'g', 'h' */
 156      LITTLENUM_TYPE *words;     /* Build the binary here.  */
 157 {
 158   FLONUM_TYPE f;
 159   LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
 160   /* Extra bits for zeroed low-order bits.  */
 161   /* The 1st MAX_PRECISION are zeroed, the last contain flonum bits.  */
 162   char *return_value;
 163   int precision;                /* Number of 16-bit words in the format.  */
 164   long int exponent_bits;
 165
 166   return_value = str;
 167   f.low = bits + MAX_PRECISION;
 168   f.high = NULL;
 169   f.leader = NULL;
 170   f.exponent = NULL;
 171   f.sign = '\0';
 172
 173   if (what_kind_of_float (what_kind, &precision, &exponent_bits))
 174     {
 175       /* We lost.  */
 176       return_value = NULL;
 177       make_invalid_floating_point_number (words);
 178     }
 179   if (return_value)
 180     {
 181       memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);
 182
 183       /* Use more LittleNums than seems necessary:
 184          the highest flonum may have 15 leading 0 bits, so could be
 185          useless.  */
 186       f.high = f.low + precision - 1 + GUARD;
 187
 188       if (atof_generic (&return_value, ".", "eE", &f))
 189         {
 190           make_invalid_floating_point_number (words);
 191           /* We lost.  */
 192           return_value = NULL;
 193         }
 194       else
 195         {
 196           if (flonum_gen2tahoe (what_kind, &f, words))
 197             return_value = NULL;
 198         }
 199     }
 200   return return_value;
 201 }
 202 \f
 203 /* In: a flonum, a Tahoe floating point format.
 204    Out: a Tahoe floating-point bit pattern.  */
 205
 206 int                             /* 0: OK.  */
 207 flonum_gen2tahoe (format_letter, f, words)
 208      char format_letter;        /* One of 'd' 'f'.  */
 209      FLONUM_TYPE *f;
 210      LITTLENUM_TYPE *words;     /* Deliver answer here.  */
 211 {
 212   LITTLENUM_TYPE *lp;
 213   int precision;
 214   long int exponent_bits;
 215   int return_value;             /* 0 == OK.  */
 216
 217   return_value =
 218     what_kind_of_float (format_letter, &precision, &exponent_bits);
 219   if (return_value != 0)
 220     {
 221       make_invalid_floating_point_number (words);
 222     }
 223   else
 224     {
 225       if (f->low > f->leader)
 226         {
 227           /* 0.0e0 seen.  */
 228           memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision);
 229         }
 230       else
 231         {
 232           long int exponent_1;
 233           long int exponent_2;
 234           long int exponent_3;
 235           long int exponent_4;
 236           int exponent_skippage;
 237           LITTLENUM_TYPE word1;
 238
 239           /* JF: Deal with new Nan, +Inf and -Inf codes.  */
 240           if (f->sign != '-' && f->sign != '+')
 241             {
 242               make_invalid_floating_point_number (words);
 243               return return_value;
 244             }
 245           /* All tahoe floating_point formats have:
 246              Bit 15 is sign bit.
 247              Bits 14:n are excess-whatever exponent.
 248              Bits n-1:0 (if any) are most significant bits of fraction.
 249              Bits 15:0 of the next word are the next most significant bits.
 250              And so on for each other word.
 251
 252              So we need: number of bits of exponent, number of bits of
 253              mantissa.  */
 254
 255           bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
 256           littlenum_pointer = f->leader;
 257           littlenum_end = f->low;
 258
 259           /* Seek (and forget) 1st significant bit.  */
 260           for (exponent_skippage = 0;
 261                !next_bits (1);
 262                exponent_skippage++)
 263             ;
 264
 265           exponent_1 = f->exponent + f->leader + 1 - f->low;
 266
 267           /* Radix LITTLENUM_RADIX, point just higher than f -> leader.  */
 268           exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
 269
 270           /* Radix 2.  */
 271           exponent_3 = exponent_2 - exponent_skippage;
 272
 273           /* Forget leading zeros, forget 1st bit.  */
 274           exponent_4 = exponent_3 + (1 << (exponent_bits - 1));
 275
 276           /* Offset exponent.  */
 277
 278           if (exponent_4 & ~mask[exponent_bits])
 279             {
 280               /* Exponent overflow. Lose immediately.  */
 281
 282               make_invalid_floating_point_number (words);
 283
 284               /* We leave return_value alone: admit we read the
 285                 number, but return a floating exception because we
 286                 can't encode the number.  */
 287             }
 288           else
 289             {
 290               lp = words;
 291
 292               /* Word 1.  Sign, exponent and perhaps high bits.  */
 293               /* Assume 2's complement integers.  */
 294               word1 = ((exponent_4 & mask[exponent_bits])
 295                        << (15 - exponent_bits))
 296                 | ((f->sign == '+') ? 0 : 0x8000)
 297                 | next_bits (15 - exponent_bits);
 298               *lp++ = word1;
 299
 300               /* The rest of the words are just mantissa bits.  */
 301               for (; lp < words + precision; lp++)
 302                 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
 303
 304               if (next_bits (1))
 305                 {
 306                   /* Since the NEXT bit is a 1, round UP the mantissa.
 307                      The cunning design of these hidden-1 floats permits
 308                      us to let the mantissa overflow into the exponent, and
 309                      it 'does the right thing'. However, we lose if the
 310                      highest-order bit of the lowest-order word flips.
 311                      Is that clear?  */
 312
 313                   unsigned long int carry;
 314
 315                   /* #if (sizeof(carry)) < ((sizeof(bits[0]) *
 316                      BITS_PER_CHAR) + 2) Please allow at least 1 more
 317                      bit in carry than is in a LITTLENUM.  We need
 318                      that extra bit to hold a carry during a LITTLENUM
 319                      carry propagation. Another extra bit (kept 0)
 320                      will assure us that we don't get a sticky sign
 321                      bit after shifting right, and that permits us to
 322                      propagate the carry without any masking of bits.
 323                      #endif  */
 324                   for (carry = 1, lp--;
 325                        carry && (lp >= words);
 326                        lp--)
 327                     {
 328                       carry = *lp + carry;
 329                       *lp = carry;
 330                       carry >>= LITTLENUM_NUMBER_OF_BITS;
 331                     }
 332
 333                   if ((word1 ^ *words)
 334                       & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
 335                     {
 336                       make_invalid_floating_point_number (words);
 337                       /* We leave return_value alone: admit we read
 338                          the number, but return a floating exception
 339                          because we can't encode the number.  */
 340                     }
 341                 }               /* if (we needed to round up)  */
 342             }                   /* if (exponent overflow)  */
 343         }                       /* if (0.0e0)  */
 344     }                           /* if (float_type was OK)  */
 345   return return_value;
 346 }
 347 \f
 348 /* In:  input_line_pointer -> the 1st character of a floating-point
 349  *              number.
 350  *      1 letter denoting the type of statement that wants a
 351  *              binary floating point number returned.
 352  *      Address of where to build floating point literal.
 353  *              Assumed to be 'big enough'.
 354  *      Address of where to return size of literal (in chars).
 355  *
 356  * Out: Input_line_pointer -> of next char after floating number.
 357  *      Error message, or 0.
 358  *      Floating point literal.
 359  *      Number of chars we used for the literal.  */
 360
 361 char *
 362 md_atof (what_statement_type, literalP, sizeP)
 363      char what_statement_type;
 364      char *literalP;
 365      int *sizeP;
 366 {
 367   LITTLENUM_TYPE words[MAX_PRECISION];
 368   register char kind_of_float;
 369   register int number_of_chars;
 370   register LITTLENUM_TYPE *littlenum_pointer;
 371
 372   switch (what_statement_type)
 373     {
 374     case 'f':                   /* .ffloat  */
 375     case 'd':                   /* .dfloat  */
 376       kind_of_float = what_statement_type;
 377       break;
 378
 379     default:
 380       kind_of_float = 0;
 381       break;
 382     }
 383
 384   if (kind_of_float)
 385     {
 386       register LITTLENUM_TYPE *limit;
 387
 388       input_line_pointer = atof_tahoe (input_line_pointer,
 389                                        kind_of_float,
 390                                        words);
 391       /* The atof_tahoe() builds up 16-bit numbers.
 392          Since the assembler may not be running on
 393          a different-endian machine, be very careful about
 394          converting words to chars.  */
 395       number_of_chars = (kind_of_float == 'f' ? F_PRECISION_CHARS :
 396                          (kind_of_float == 'd' ? D_PRECISION_CHARS : 0));
 397       know (number_of_chars <= MAX_PRECISION * sizeof (LITTLENUM_TYPE));
 398       limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
 399       for (littlenum_pointer = words;
 400            littlenum_pointer < limit;
 401            littlenum_pointer++)
 402         {
 403           md_number_to_chars (literalP, *littlenum_pointer,
 404                               sizeof (LITTLENUM_TYPE));
 405           literalP += sizeof (LITTLENUM_TYPE);
 406         }
 407     }
 408   else
 409     {
 410       number_of_chars = 0;
 411     }
 412
 413   *sizeP = number_of_chars;
 414   return kind_of_float ? 0 : _("Bad call to md_atof()");
 415 }