gas/config/atof-ieee.c

   1 /* atof_ieee.c - turn a Flonum into an IEEE floating point number
   2    Copyright (C) 1987, 1992 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 2, 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
  18    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 #include "as.h"
  21
  22 #ifdef USG
  23 #define bzero(s,n) memset(s,0,n)
  24 #define bcopy(from,to,n) memcpy((to),(from),(n))
  25 #endif
  26
  27 extern FLONUM_TYPE generic_floating_point_number; /* Flonums returned here. */
  28
  29 #ifndef NULL
  30 #define NULL (0)
  31 #endif
  32
  33 extern char EXP_CHARS[];
  34 /* Precision in LittleNums. */
  35 #define MAX_PRECISION (6)
  36 #define F_PRECISION (2)
  37 #define D_PRECISION (4)
  38 #define X_PRECISION (6)
  39 #define P_PRECISION (6)
  40
  41 /* Length in LittleNums of guard bits. */
  42 #define GUARD (2)
  43
  44 static unsigned long mask [] = {
  45         0x00000000,
  46         0x00000001,
  47         0x00000003,
  48         0x00000007,
  49         0x0000000f,
  50         0x0000001f,
  51         0x0000003f,
  52         0x0000007f,
  53         0x000000ff,
  54         0x000001ff,
  55         0x000003ff,
  56         0x000007ff,
  57         0x00000fff,
  58         0x00001fff,
  59         0x00003fff,
  60         0x00007fff,
  61         0x0000ffff,
  62         0x0001ffff,
  63         0x0003ffff,
  64         0x0007ffff,
  65         0x000fffff,
  66         0x001fffff,
  67         0x003fffff,
  68         0x007fffff,
  69         0x00ffffff,
  70         0x01ffffff,
  71         0x03ffffff,
  72         0x07ffffff,
  73         0x0fffffff,
  74         0x1fffffff,
  75         0x3fffffff,
  76         0x7fffffff,
  77         0xffffffff,
  78 };
  79 \f
  80
  81 static int bits_left_in_littlenum;
  82 static int littlenums_left;
  83 static LITTLENUM_TYPE *littlenum_pointer;
  84
  85 static int
  86     next_bits (number_of_bits)
  87 int number_of_bits;
  88 {
  89         int return_value;
  90
  91         if (!littlenums_left)
  92             return(0);
  93         if (number_of_bits >= bits_left_in_littlenum) {
  94                 return_value  = mask[bits_left_in_littlenum] & *littlenum_pointer;
  95                 number_of_bits -= bits_left_in_littlenum;
  96                 return_value <<= number_of_bits;
  97
  98                 if (--littlenums_left) {
  99                         bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
 100                         --littlenum_pointer;
 101                         return_value |= (*littlenum_pointer >> bits_left_in_littlenum) & mask[number_of_bits];
 102                 }
 103         } else {
 104                 bits_left_in_littlenum -= number_of_bits;
 105                 return_value = mask[number_of_bits] & (*littlenum_pointer >> bits_left_in_littlenum);
 106         }
 107         return(return_value);
 108 }
 109
 110 /* Num had better be less than LITTLENUM_NUMBER_OF_BITS */
 111 static void
 112     unget_bits(num)
 113 int num;
 114 {
 115         if (!littlenums_left) {
 116                 ++littlenum_pointer;
 117                 ++littlenums_left;
 118                 bits_left_in_littlenum = num;
 119         } else if (bits_left_in_littlenum + num > LITTLENUM_NUMBER_OF_BITS) {
 120                 bits_left_in_littlenum = num - (LITTLENUM_NUMBER_OF_BITS - bits_left_in_littlenum);
 121                 ++littlenum_pointer;
 122                 ++littlenums_left;
 123         } else
 124             bits_left_in_littlenum += num;
 125 }
 126
 127 static void
 128   make_invalid_floating_point_number(words)
 129 LITTLENUM_TYPE *words;
 130 {
 131         as_bad("cannot create floating-point number");
 132         words[0] = ((unsigned) -1) >> 1; /* Zero the leftmost bit */
 133         words[1] = -1;
 134         words[2] = -1;
 135         words[3] = -1;
 136         words[4] = -1;
 137         words[5] = -1;
 138 }
 139 \f
 140 /***********************************************************************\
 141  *      Warning: this returns 16-bit LITTLENUMs. It is up to the caller *
 142  *      to figure out any alignment problems and to conspire for the    *
 143  *      bytes/word to be emitted in the right order. Bigendians beware! *
 144  *                                                                      *
 145  \***********************************************************************/
 146
 147 /* Note that atof-ieee always has X and P precisions enabled.  it is up
 148    to md_atof to filter them out if the target machine does not support
 149    them.  */
 150
 151 char *                          /* Return pointer past text consumed. */
 152   atof_ieee(str, what_kind, words)
 153 char *str;      /* Text to convert to binary. */
 154 char what_kind; /* 'd', 'f', 'g', 'h' */
 155 LITTLENUM_TYPE *words;  /* Build the binary here. */
 156 {
 157         static LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
 158         /* Extra bits for zeroed low-order bits. */
 159         /* The 1st MAX_PRECISION are zeroed, */
 160         /* the last contain flonum bits. */
 161         char *return_value;
 162         int precision; /* Number of 16-bit words in the format. */
 163         long exponent_bits;
 164         FLONUM_TYPE save_gen_flonum;
 165
 166         /* We have to save the generic_floating_point_number because it
 167            contains storage allocation about the array of LITTLENUMs
 168            where the value is actually stored.  We will allocate our
 169            own array of littlenums below, but have to restore the global
 170            one on exit.  */
 171         save_gen_flonum = generic_floating_point_number;
 172
 173         return_value = str;
 174         generic_floating_point_number.low       = bits + MAX_PRECISION;
 175         generic_floating_point_number.high      = NULL;
 176         generic_floating_point_number.leader    = NULL;
 177         generic_floating_point_number.exponent  = NULL;
 178         generic_floating_point_number.sign      = '\0';
 179
 180         /* Use more LittleNums than seems */
 181         /* necessary: the highest flonum may have */
 182         /* 15 leading 0 bits, so could be useless. */
 183
 184         bzero(bits, sizeof(LITTLENUM_TYPE) * MAX_PRECISION);
 185
 186         switch (what_kind) {
 187         case 'f':
 188         case 'F':
 189         case 's':
 190         case 'S':
 191                 precision = F_PRECISION;
 192                 exponent_bits = 8;
 193                 break;
 194
 195         case 'd':
 196         case 'D':
 197         case 'r':
 198         case 'R':
 199                 precision = D_PRECISION;
 200                 exponent_bits = 11;
 201                 break;
 202
 203         case 'x':
 204         case 'X':
 205         case 'e':
 206         case 'E':
 207                 precision = X_PRECISION;
 208                 exponent_bits = 15;
 209                 break;
 210
 211         case 'p':
 212         case 'P':
 213
 214                 precision = P_PRECISION;
 215                 exponent_bits = -1;
 216                 break;
 217
 218         default:
 219                 make_invalid_floating_point_number(words);
 220                 return(NULL);
 221         }
 222
 223         generic_floating_point_number.high = generic_floating_point_number.low + precision - 1 + GUARD;
 224
 225         if (atof_generic(&return_value, ".", EXP_CHARS, &generic_floating_point_number)) {
 226                 /* as_bad("Error converting floating point number (Exponent overflow?)"); */
 227                 make_invalid_floating_point_number(words);
 228                 return(NULL);
 229         }
 230         gen_to_words(words, precision, exponent_bits);
 231
 232         /* Restore the generic_floating_point_number's storage alloc
 233            (and everything else).  */
 234         generic_floating_point_number = save_gen_flonum;
 235
 236         return(return_value);
 237 }
 238
 239 /* Turn generic_floating_point_number into a real float/double/extended */
 240 int gen_to_words(words, precision, exponent_bits)
 241 LITTLENUM_TYPE *words;
 242 int precision;
 243 long exponent_bits;
 244 {
 245         int return_value = 0;
 246
 247         long exponent_1;
 248         long exponent_2;
 249         long exponent_3;
 250         long exponent_4;
 251         int exponent_skippage;
 252         LITTLENUM_TYPE word1;
 253         LITTLENUM_TYPE *lp;
 254
 255         if (generic_floating_point_number.low > generic_floating_point_number.leader) {
 256                 /* 0.0e0 seen. */
 257                 if (generic_floating_point_number.sign == '+')
 258                     words[0] = 0x0000;
 259                 else
 260                     words[0] = 0x8000;
 261                 bzero(&words[1], sizeof(LITTLENUM_TYPE) * (precision - 1));
 262                 return(return_value);
 263         }
 264
 265         /* NaN:  Do the right thing */
 266         if (generic_floating_point_number.sign == 0) {
 267                 if (precision == F_PRECISION) {
 268                         words[0] = 0x7fff;
 269                         words[1] = 0xffff;
 270                 } else {
 271                         words[0] = 0x7fff;
 272                         words[1] = 0xffff;
 273                         words[2] = 0xffff;
 274                         words[3] = 0xffff;
 275                 }
 276                 return return_value;
 277         } else if (generic_floating_point_number.sign == 'P') {
 278                 /* +INF:  Do the right thing */
 279                 if (precision == F_PRECISION) {
 280                         words[0] = 0x7f80;
 281                         words[1] = 0;
 282                 } else {
 283                         words[0] = 0x7ff0;
 284                         words[1] = 0;
 285                         words[2] = 0;
 286                         words[3] = 0;
 287                 }
 288                 return(return_value);
 289         } else if (generic_floating_point_number.sign == 'N') {
 290                 /* Negative INF */
 291                 if (precision == F_PRECISION) {
 292                         words[0] = 0xff80;
 293                         words[1] = 0x0;
 294                 } else {
 295                         words[0] = 0xfff0;
 296                         words[1] = 0x0;
 297                         words[2] = 0x0;
 298                         words[3] = 0x0;
 299                 }
 300                 return(return_value);
 301         }
 302         /*
 303          * The floating point formats we support have:
 304          * Bit 15 is sign bit.
 305          * Bits 14:n are excess-whatever exponent.
 306          * Bits n-1:0 (if any) are most significant bits of fraction.
 307          * Bits 15:0 of the next word(s) are the next most significant bits.
 308          *
 309          * So we need: number of bits of exponent, number of bits of
 310          * mantissa.
 311          */
 312         bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
 313         littlenum_pointer = generic_floating_point_number.leader;
 314         littlenums_left = 1 + generic_floating_point_number.leader - generic_floating_point_number.low;
 315         /* Seek (and forget) 1st significant bit */
 316         for (exponent_skippage = 0;! next_bits(1); exponent_skippage ++) ;;
 317         exponent_1 = generic_floating_point_number.exponent + generic_floating_point_number.leader
 318           + 1 - generic_floating_point_number.low;
 319         /* Radix LITTLENUM_RADIX, point just higher than generic_floating_point_number.leader. */
 320         exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
 321         /* Radix 2. */
 322         exponent_3 = exponent_2 - exponent_skippage;
 323         /* Forget leading zeros, forget 1st bit. */
 324         exponent_4 = exponent_3 + ((1 << (exponent_bits - 1)) - 2);
 325         /* Offset exponent. */
 326
 327         lp = words;
 328
 329         /* Word 1. Sign, exponent and perhaps high bits. */
 330         word1 = (generic_floating_point_number.sign == '+') ? 0 : (1 << (LITTLENUM_NUMBER_OF_BITS - 1));
 331
 332         /* Assume 2's complement integers. */
 333         if (exponent_4 < 1 && exponent_4 >= -62) {
 334                 int prec_bits;
 335                 int num_bits;
 336
 337                 unget_bits(1);
 338                 num_bits = -exponent_4;
 339                 prec_bits = LITTLENUM_NUMBER_OF_BITS * precision - (exponent_bits + 1 + num_bits);
 340                 if(precision == X_PRECISION && exponent_bits == 15)
 341                     prec_bits -= LITTLENUM_NUMBER_OF_BITS + 1;
 342
 343                 if (num_bits >= LITTLENUM_NUMBER_OF_BITS - exponent_bits) {
 344                         /* Bigger than one littlenum */
 345                         num_bits -= (LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits;
 346                         *lp++ = word1;
 347                         if (num_bits + exponent_bits + 1 >= precision * LITTLENUM_NUMBER_OF_BITS) {
 348                                 /* Exponent overflow */
 349                                 make_invalid_floating_point_number(words);
 350                                 return(return_value);
 351                         }
 352                         if (precision == X_PRECISION && exponent_bits == 15) {
 353                                 *lp++ = 0;
 354                                 *lp++ = 0;
 355                                 num_bits -= LITTLENUM_NUMBER_OF_BITS - 1;
 356                         }
 357                         while (num_bits >= LITTLENUM_NUMBER_OF_BITS) {
 358                                 num_bits -= LITTLENUM_NUMBER_OF_BITS;
 359                                 *lp++ = 0;
 360                         }
 361                         if (num_bits)
 362                             *lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - (num_bits));
 363                 } else {
 364                         if (precision == X_PRECISION && exponent_bits == 15) {
 365                                 *lp++ = word1;
 366                                 *lp++ = 0;
 367                                 if (num_bits == LITTLENUM_NUMBER_OF_BITS) {
 368                                         *lp++ = 0;
 369                                         *lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - 1);
 370                                 } else if (num_bits == LITTLENUM_NUMBER_OF_BITS - 1)
 371                                     *lp++ = 0;
 372                                 else
 373                                     *lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - 1 - num_bits);
 374                                 num_bits = 0;
 375                         } else {
 376                                 word1 |= next_bits((LITTLENUM_NUMBER_OF_BITS - 1) - (exponent_bits + num_bits));
 377                                 *lp++ = word1;
 378                         }
 379                 }
 380                 while (lp < words + precision)
 381                     *lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS);
 382
 383                 /* Round the mantissa up, but don't change the number */
 384                 if (next_bits(1)) {
 385                         --lp;
 386                         if (prec_bits > LITTLENUM_NUMBER_OF_BITS) {
 387                                 int n = 0;
 388                                 int tmp_bits;
 389
 390                                 n = 0;
 391                                 tmp_bits = prec_bits;
 392                                 while (tmp_bits > LITTLENUM_NUMBER_OF_BITS) {
 393                                         if (lp[n] != (LITTLENUM_TYPE) - 1)
 394                                             break;
 395                                         --n;
 396                                         tmp_bits -= LITTLENUM_NUMBER_OF_BITS;
 397                                 }
 398                                 if (tmp_bits > LITTLENUM_NUMBER_OF_BITS || (lp[n] & mask[tmp_bits]) != mask[tmp_bits]) {
 399                                         unsigned long carry;
 400
 401                                         for (carry = 1; carry && (lp >= words); lp --) {
 402                                                 carry = *lp + carry;
 403                                                 *lp = carry;
 404                                                 carry >>= LITTLENUM_NUMBER_OF_BITS;
 405                                         }
 406                                 }
 407                         } else if ((*lp & mask[prec_bits]) != mask[prec_bits])
 408                             lp++;
 409                 }
 410
 411                 return return_value;
 412         } else  if (exponent_4 & ~ mask [exponent_bits]) {
 413                 /*
 414                  * Exponent overflow. Lose immediately.
 415                  */
 416
 417                 /*
 418                  * We leave return_value alone: admit we read the
 419                  * number, but return a floating exception
 420                  * because we can't encode the number.
 421                  */
 422                 make_invalid_floating_point_number (words);
 423                 return return_value;
 424         } else {
 425                 word1 |=  (exponent_4 << ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits))
 426                     | next_bits ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits);
 427         }
 428
 429         *lp++ = word1;
 430
 431         /* X_PRECISION is special: it has 16 bits of zero in the middle,
 432            followed by a 1 bit. */
 433         if (exponent_bits == 15 && precision == X_PRECISION) {
 434                 *lp++ = 0;
 435                 *lp++ = 1 << (LITTLENUM_NUMBER_OF_BITS) | next_bits(LITTLENUM_NUMBER_OF_BITS - 1);
 436         }
 437
 438         /* The rest of the words are just mantissa bits. */
 439         while(lp < words + precision)
 440             *lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS);
 441
 442         if (next_bits(1)) {
 443                 unsigned long carry;
 444                 /*
 445                  * Since the NEXT bit is a 1, round UP the mantissa.
 446                  * The cunning design of these hidden-1 floats permits
 447                  * us to let the mantissa overflow into the exponent, and
 448                  * it 'does the right thing'. However, we lose if the
 449                  * highest-order bit of the lowest-order word flips.
 450                  * Is that clear?
 451                  */
 452
 453                 /* #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
 454                    Please allow at least 1 more bit in carry than is in a LITTLENUM.
 455                    We need that extra bit to hold a carry during a LITTLENUM carry
 456                    propagation. Another extra bit (kept 0) will assure us that we
 457                    don't get a sticky sign bit after shifting right, and that
 458                    permits us to propagate the carry without any masking of bits.
 459                    #endif */
 460                 for (carry = 1, lp--; carry && (lp >= words); lp--) {
 461                         carry = *lp + carry;
 462                         *lp = carry;
 463                         carry >>= LITTLENUM_NUMBER_OF_BITS;
 464                 }
 465                 if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1))) {
 466                         /* We leave return_value alone: admit we read the
 467                          * number, but return a floating exception
 468                          * because we can't encode the number.
 469                          */
 470                         *words &= ~(1 << (LITTLENUM_NUMBER_OF_BITS - 1));
 471                         /* make_invalid_floating_point_number (words); */
 472                         /* return return_value; */
 473                 }
 474         }
 475         return (return_value);
 476 }
 477
 478 /* This routine is a real kludge.  Someone really should do it better, but
 479    I'm too lazy, and I don't understand this stuff all too well anyway
 480    (JF)
 481    */
 482 void
 483     int_to_gen(x)
 484 long x;
 485 {
 486         char buf[20];
 487         char *bufp;
 488
 489         sprintf(buf,"%ld",x);
 490         bufp = &buf[0];
 491         if (atof_generic(&bufp, ".", EXP_CHARS, &generic_floating_point_number))
 492             as_bad("Error converting number to floating point (Exponent overflow?)");
 493 }
 494
 495 #ifdef TEST
 496 char *
 497     print_gen(gen)
 498 FLONUM_TYPE *gen;
 499 {
 500         FLONUM_TYPE f;
 501         LITTLENUM_TYPE arr[10];
 502         double dv;
 503         float fv;
 504         static char sbuf[40];
 505
 506         if (gen) {
 507                 f = generic_floating_point_number;
 508                 generic_floating_point_number = *gen;
 509         }
 510         gen_to_words(&arr[0], 4, 11);
 511         bcopy(&arr[0], &dv, sizeof(double));
 512         sprintf(sbuf, "%x %x %x %x %.14G   ", arr[0], arr[1], arr[2], arr[3], dv);
 513         gen_to_words(&arr[0],2,8);
 514         bcopy(&arr[0],&fv,sizeof(float));
 515         sprintf(sbuf + strlen(sbuf), "%x %x %.12g\n", arr[0], arr[1],
 516                 fv);
 517
 518         if (gen) {
 519                 generic_floating_point_number = f;
 520         }
 521
 522         return(sbuf);
 523 }
 524 #endif
 525
 526 /* end of atof-ieee.c */