gas/config/atof-vax.c

   1 /* atof_vax.c - turn a Flonum into a VAX floating point number
   2    Copyright (C) 1987-2018 Free Software Foundation, Inc.
   3
   4    This file is part of GAS, the GNU Assembler.
   5
   6    GAS is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GAS is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GAS; see the file COPYING.  If not, write to the Free
  18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  19    02110-1301, USA.  */
  20
  21 #include "as.h"
  22
  23 /* Precision in LittleNums.  */
  24 #define MAX_PRECISION   8
  25 #define H_PRECISION     8
  26 #define G_PRECISION     4
  27 #define D_PRECISION     4
  28 #define F_PRECISION     2
  29
  30 /* Length in LittleNums of guard bits.  */
  31 #define GUARD           2
  32
  33 int flonum_gen2vax (int, FLONUM_TYPE *, LITTLENUM_TYPE *);
  34
  35 /* Number of chars in flonum type 'letter'.  */
  36
  37 static unsigned int
  38 atof_vax_sizeof (int letter)
  39 {
  40   int return_value;
  41
  42   /* Permitting uppercase letters is probably a bad idea.
  43      Please use only lower-cased letters in case the upper-cased
  44      ones become unsupported!  */
  45   switch (letter)
  46     {
  47     case 'f':
  48     case 'F':
  49       return_value = 4;
  50       break;
  51
  52     case 'd':
  53     case 'D':
  54     case 'g':
  55     case 'G':
  56       return_value = 8;
  57       break;
  58
  59     case 'h':
  60     case 'H':
  61       return_value = 16;
  62       break;
  63
  64     default:
  65       return_value = 0;
  66       break;
  67     }
  68
  69   return return_value;
  70 }
  71
  72 static const long mask[] =
  73 {
  74   0x00000000,
  75   0x00000001,
  76   0x00000003,
  77   0x00000007,
  78   0x0000000f,
  79   0x0000001f,
  80   0x0000003f,
  81   0x0000007f,
  82   0x000000ff,
  83   0x000001ff,
  84   0x000003ff,
  85   0x000007ff,
  86   0x00000fff,
  87   0x00001fff,
  88   0x00003fff,
  89   0x00007fff,
  90   0x0000ffff,
  91   0x0001ffff,
  92   0x0003ffff,
  93   0x0007ffff,
  94   0x000fffff,
  95   0x001fffff,
  96   0x003fffff,
  97   0x007fffff,
  98   0x00ffffff,
  99   0x01ffffff,
 100   0x03ffffff,
 101   0x07ffffff,
 102   0x0fffffff,
 103   0x1fffffff,
 104   0x3fffffff,
 105   0x7fffffff,
 106   0xffffffff
 107 };
 108 \f
 109
 110 /* Shared between flonum_gen2vax and next_bits.  */
 111 static int bits_left_in_littlenum;
 112 static LITTLENUM_TYPE *littlenum_pointer;
 113 static LITTLENUM_TYPE *littlenum_end;
 114
 115 static int
 116 next_bits (int number_of_bits)
 117 {
 118   int return_value;
 119
 120   if (littlenum_pointer < littlenum_end)
 121     return 0;
 122   if (number_of_bits >= bits_left_in_littlenum)
 123     {
 124       return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
 125       number_of_bits -= bits_left_in_littlenum;
 126       return_value <<= number_of_bits;
 127       bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
 128       littlenum_pointer--;
 129       if (littlenum_pointer >= littlenum_end)
 130         return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) & mask[number_of_bits];
 131     }
 132   else
 133     {
 134       bits_left_in_littlenum -= number_of_bits;
 135       return_value = mask[number_of_bits] & ((*littlenum_pointer) >> bits_left_in_littlenum);
 136     }
 137   return return_value;
 138 }
 139
 140 static void
 141 make_invalid_floating_point_number (LITTLENUM_TYPE *words)
 142 {
 143   *words = 0x8000;              /* Floating Reserved Operand Code.  */
 144 }
 145
 146 \f
 147 static int                      /* 0 means letter is OK.  */
 148 what_kind_of_float (int letter,                 /* In: lowercase please. What kind of float?  */
 149                     int *precisionP,            /* Number of 16-bit words in the float.  */
 150                     long *exponent_bitsP)       /* Number of exponent bits.  */
 151 {
 152   int retval;
 153
 154   retval = 0;
 155   switch (letter)
 156     {
 157     case 'f':
 158       *precisionP = F_PRECISION;
 159       *exponent_bitsP = 8;
 160       break;
 161
 162     case 'd':
 163       *precisionP = D_PRECISION;
 164       *exponent_bitsP = 8;
 165       break;
 166
 167     case 'g':
 168       *precisionP = G_PRECISION;
 169       *exponent_bitsP = 11;
 170       break;
 171
 172     case 'h':
 173       *precisionP = H_PRECISION;
 174       *exponent_bitsP = 15;
 175       break;
 176
 177     default:
 178       retval = 69;
 179       break;
 180     }
 181   return retval;
 182 }
 183 \f
 184 /* Warning: this returns 16-bit LITTLENUMs, because that is
 185    what the VAX thinks in. It is up to the caller to figure
 186    out any alignment problems and to conspire for the bytes/word
 187    to be emitted in the right order. Bigendians beware!  */
 188
 189 static char *
 190 atof_vax (char *str,                    /* Text to convert to binary.  */
 191           int what_kind,                /* 'd', 'f', 'g', 'h'  */
 192           LITTLENUM_TYPE *words)        /* Build the binary here.  */
 193 {
 194   FLONUM_TYPE f;
 195   LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
 196   /* Extra bits for zeroed low-order bits.
 197      The 1st MAX_PRECISION are zeroed,
 198      the last contain flonum bits.  */
 199   char *return_value;
 200   int precision;                /* Number of 16-bit words in the format.  */
 201   long exponent_bits;
 202
 203   return_value = str;
 204   f.low = bits + MAX_PRECISION;
 205   f.high = NULL;
 206   f.leader = NULL;
 207   f.exponent = 0;
 208   f.sign = '\0';
 209
 210   if (what_kind_of_float (what_kind, &precision, &exponent_bits))
 211     {
 212       return_value = NULL;
 213       make_invalid_floating_point_number (words);
 214     }
 215
 216   if (return_value)
 217     {
 218       memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);
 219
 220       /* Use more LittleNums than seems
 221          necessary: the highest flonum may have
 222          15 leading 0 bits, so could be useless.  */
 223       f.high = f.low + precision - 1 + GUARD;
 224
 225       if (atof_generic (&return_value, ".", "eE", &f))
 226         {
 227           make_invalid_floating_point_number (words);
 228           return_value = NULL;
 229         }
 230       else if (flonum_gen2vax (what_kind, &f, words))
 231         return_value = NULL;
 232     }
 233
 234   return return_value;
 235 }
 236 \f
 237 /* In: a flonum, a vax floating point format.
 238    Out: a vax floating-point bit pattern.  */
 239
 240 int
 241 flonum_gen2vax (int format_letter,      /* One of 'd' 'f' 'g' 'h'.  */
 242                 FLONUM_TYPE *f,
 243                 LITTLENUM_TYPE *words)  /* Deliver answer here.  */
 244 {
 245   LITTLENUM_TYPE *lp;
 246   int precision;
 247   long exponent_bits;
 248   int return_value;             /* 0 == OK.  */
 249
 250   return_value = what_kind_of_float (format_letter, &precision, &exponent_bits);
 251
 252   if (return_value != 0)
 253     make_invalid_floating_point_number (words);
 254
 255   else
 256     {
 257       if (f->low > f->leader)
 258         /* 0.0e0 seen.  */
 259         memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision);
 260
 261       else
 262         {
 263           long exponent_1;
 264           long exponent_2;
 265           long exponent_3;
 266           long exponent_4;
 267           int exponent_skippage;
 268           LITTLENUM_TYPE word1;
 269
 270           /* JF: Deal with new Nan, +Inf and -Inf codes.  */
 271           if (f->sign != '-' && f->sign != '+')
 272             {
 273               make_invalid_floating_point_number (words);
 274               return return_value;
 275             }
 276
 277           /* All vaxen floating_point formats (so far) have:
 278              Bit 15 is sign bit.
 279              Bits 14:n are excess-whatever exponent.
 280              Bits n-1:0 (if any) are most significant bits of fraction.
 281              Bits 15:0 of the next word are the next most significant bits.
 282              And so on for each other word.
 283
 284              All this to be compatible with a KF11?? (Which is still faster
 285              than lots of vaxen I can think of, but it also has higher
 286              maintenance costs ... sigh).
 287
 288              So we need: number of bits of exponent, number of bits of
 289              mantissa.  */
 290
 291           bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
 292           littlenum_pointer = f->leader;
 293           littlenum_end = f->low;
 294           /* Seek (and forget) 1st significant bit.  */
 295           for (exponent_skippage = 0;
 296                !next_bits (1);
 297                exponent_skippage++);
 298
 299           exponent_1 = f->exponent + f->leader + 1 - f->low;
 300           /* Radix LITTLENUM_RADIX, point just higher than f->leader.  */
 301           exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
 302           /* Radix 2.  */
 303           exponent_3 = exponent_2 - exponent_skippage;
 304           /* Forget leading zeros, forget 1st bit.  */
 305           exponent_4 = exponent_3 + (1 << (exponent_bits - 1));
 306           /* Offset exponent.  */
 307
 308           if (exponent_4 & ~mask[exponent_bits])
 309             {
 310               /* Exponent overflow. Lose immediately.  */
 311               make_invalid_floating_point_number (words);
 312
 313               /* We leave return_value alone: admit we read the
 314                  number, but return a floating exception
 315                  because we can't encode the number.  */
 316             }
 317           else
 318             {
 319               lp = words;
 320
 321               /* Word 1. Sign, exponent and perhaps high bits.
 322                  Assume 2's complement integers.  */
 323               word1 = (((exponent_4 & mask[exponent_bits]) << (15 - exponent_bits))
 324                        | ((f->sign == '+') ? 0 : 0x8000)
 325                        | next_bits (15 - exponent_bits));
 326               *lp++ = word1;
 327
 328               /* The rest of the words are just mantissa bits.  */
 329               for (; lp < words + precision; lp++)
 330                 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
 331
 332               if (next_bits (1))
 333                 {
 334                   /* Since the NEXT bit is a 1, round UP the mantissa.
 335                      The cunning design of these hidden-1 floats permits
 336                      us to let the mantissa overflow into the exponent, and
 337                      it 'does the right thing'. However, we lose if the
 338                      highest-order bit of the lowest-order word flips.
 339                      Is that clear?  */
 340                   unsigned long carry;
 341
 342                   /*
 343                     #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
 344                     Please allow at least 1 more bit in carry than is in a LITTLENUM.
 345                     We need that extra bit to hold a carry during a LITTLENUM carry
 346                     propagation. Another extra bit (kept 0) will assure us that we
 347                     don't get a sticky sign bit after shifting right, and that
 348                     permits us to propagate the carry without any masking of bits.
 349                     #endif   */
 350                   for (carry = 1, lp--;
 351                        carry && (lp >= words);
 352                        lp--)
 353                     {
 354                       carry = *lp + carry;
 355                       *lp = carry;
 356                       carry >>= LITTLENUM_NUMBER_OF_BITS;
 357                     }
 358
 359                   if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
 360                     {
 361                       make_invalid_floating_point_number (words);
 362                       /* We leave return_value alone: admit we read the
 363                          number, but return a floating exception
 364                          because we can't encode the number.  */
 365                     }
 366                 }
 367             }
 368         }
 369     }
 370   return return_value;
 371 }
 372
 373 /* JF this used to be in vax.c but this looks like a better place for it.  */
 374
 375 /* In:  input_line_pointer->the 1st character of a floating-point
 376                 number.
 377         1 letter denoting the type of statement that wants a
 378                 binary floating point number returned.
 379         Address of where to build floating point literal.
 380                 Assumed to be 'big enough'.
 381         Address of where to return size of literal (in chars).
 382
 383    Out: Input_line_pointer->of next char after floating number.
 384         Error message, or 0.
 385         Floating point literal.
 386         Number of chars we used for the literal.  */
 387
 388 #define MAXIMUM_NUMBER_OF_LITTLENUMS  8         /* For .hfloats.  */
 389
 390 const char *
 391 vax_md_atof (int what_statement_type,
 392              char *literalP,
 393              int *sizeP)
 394 {
 395   LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS];
 396   char kind_of_float;
 397   unsigned int number_of_chars;
 398   LITTLENUM_TYPE *littlenumP;
 399
 400   switch (what_statement_type)
 401     {
 402     case 'F':
 403     case 'f':
 404       kind_of_float = 'f';
 405       break;
 406
 407     case 'D':
 408     case 'd':
 409       kind_of_float = 'd';
 410       break;
 411
 412     case 'g':
 413       kind_of_float = 'g';
 414       break;
 415
 416     case 'h':
 417       kind_of_float = 'h';
 418       break;
 419
 420     default:
 421       kind_of_float = 0;
 422       break;
 423     };
 424
 425   if (kind_of_float)
 426     {
 427       LITTLENUM_TYPE *limit;
 428
 429       input_line_pointer = atof_vax (input_line_pointer,
 430                                      kind_of_float,
 431                                      words);
 432       /* The atof_vax() builds up 16-bit numbers.
 433          Since the assembler may not be running on
 434          a little-endian machine, be very careful about
 435          converting words to chars.  */
 436       number_of_chars = atof_vax_sizeof (kind_of_float);
 437       know (number_of_chars <= MAXIMUM_NUMBER_OF_LITTLENUMS * sizeof (LITTLENUM_TYPE));
 438       limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
 439       for (littlenumP = words; littlenumP < limit; littlenumP++)
 440         {
 441           md_number_to_chars (literalP, *littlenumP, sizeof (LITTLENUM_TYPE));
 442           literalP += sizeof (LITTLENUM_TYPE);
 443         };
 444     }
 445   else
 446     number_of_chars = 0;
 447
 448   *sizeP = number_of_chars;
 449   return kind_of_float ? NULL : _("Unrecognized or unsupported floating point constant");
 450 }