gas/config/atof-ieee.c

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