1 /* atof_vax.c - turn a Flonum into a VAX floating point number 2 Copyright 1987, 1992, 1993, 1995, 1997, 1999, 2000, 2005, 2007 3 Free Software Foundation, Inc. 4 5 This file is part of GAS, the GNU Assembler. 6 7 GAS is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3, or (at your option) 10 any later version. 11 12 GAS is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GAS; see the file COPYING. If not, write to the Free 19 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA 20 02110-1301, USA. */ 21 22 #include "as.h" 23 24 /* Precision in LittleNums. */ 25 #define MAX_PRECISION 8 26 #define H_PRECISION 8 27 #define G_PRECISION 4 28 #define D_PRECISION 4 29 #define F_PRECISION 2 30 31 /* Length in LittleNums of guard bits. */ 32 #define GUARD 2 33 34 int flonum_gen2vax (int, FLONUM_TYPE *, LITTLENUM_TYPE *); 35 36 /* Number of chars in flonum type 'letter'. */ 37 38 static unsigned int 39 atof_vax_sizeof (int letter) 40 { 41 int return_value; 42 43 /* Permitting uppercase letters is probably a bad idea. 44 Please use only lower-cased letters in case the upper-cased 45 ones become unsupported! */ 46 switch (letter) 47 { 48 case 'f': 49 case 'F': 50 return_value = 4; 51 break; 52 53 case 'd': 54 case 'D': 55 case 'g': 56 case 'G': 57 return_value = 8; 58 break; 59 60 case 'h': 61 case 'H': 62 return_value = 16; 63 break; 64 65 default: 66 return_value = 0; 67 break; 68 } 69 70 return return_value; 71 } 72 73 static const long mask[] = 74 { 75 0x00000000, 76 0x00000001, 77 0x00000003, 78 0x00000007, 79 0x0000000f, 80 0x0000001f, 81 0x0000003f, 82 0x0000007f, 83 0x000000ff, 84 0x000001ff, 85 0x000003ff, 86 0x000007ff, 87 0x00000fff, 88 0x00001fff, 89 0x00003fff, 90 0x00007fff, 91 0x0000ffff, 92 0x0001ffff, 93 0x0003ffff, 94 0x0007ffff, 95 0x000fffff, 96 0x001fffff, 97 0x003fffff, 98 0x007fffff, 99 0x00ffffff, 100 0x01ffffff, 101 0x03ffffff, 102 0x07ffffff, 103 0x0fffffff, 104 0x1fffffff, 105 0x3fffffff, 106 0x7fffffff, 107 0xffffffff 108 }; 109 110 111 /* Shared between flonum_gen2vax and next_bits. */ 112 static int bits_left_in_littlenum; 113 static LITTLENUM_TYPE *littlenum_pointer; 114 static LITTLENUM_TYPE *littlenum_end; 115 116 static int 117 next_bits (int number_of_bits) 118 { 119 int return_value; 120 121 if (littlenum_pointer < littlenum_end) 122 return 0; 123 if (number_of_bits >= bits_left_in_littlenum) 124 { 125 return_value = mask[bits_left_in_littlenum] & *littlenum_pointer; 126 number_of_bits -= bits_left_in_littlenum; 127 return_value <<= number_of_bits; 128 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits; 129 littlenum_pointer--; 130 if (littlenum_pointer >= littlenum_end) 131 return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) & mask[number_of_bits]; 132 } 133 else 134 { 135 bits_left_in_littlenum -= number_of_bits; 136 return_value = mask[number_of_bits] & ((*littlenum_pointer) >> bits_left_in_littlenum); 137 } 138 return return_value; 139 } 140 141 static void 142 make_invalid_floating_point_number (LITTLENUM_TYPE *words) 143 { 144 *words = 0x8000; /* Floating Reserved Operand Code. */ 145 } 146 147 148 static int /* 0 means letter is OK. */ 149 what_kind_of_float (int letter, /* In: lowercase please. What kind of float? */ 150 int *precisionP, /* Number of 16-bit words in the float. */ 151 long *exponent_bitsP) /* Number of exponent bits. */ 152 { 153 int retval; 154 155 retval = 0; 156 switch (letter) 157 { 158 case 'f': 159 *precisionP = F_PRECISION; 160 *exponent_bitsP = 8; 161 break; 162 163 case 'd': 164 *precisionP = D_PRECISION; 165 *exponent_bitsP = 8; 166 break; 167 168 case 'g': 169 *precisionP = G_PRECISION; 170 *exponent_bitsP = 11; 171 break; 172 173 case 'h': 174 *precisionP = H_PRECISION; 175 *exponent_bitsP = 15; 176 break; 177 178 default: 179 retval = 69; 180 break; 181 } 182 return retval; 183 } 184 185 /* Warning: this returns 16-bit LITTLENUMs, because that is 186 what the VAX thinks in. It is up to the caller to figure 187 out any alignment problems and to conspire for the bytes/word 188 to be emitted in the right order. Bigendians beware! */ 189 190 static char * 191 atof_vax (char *str, /* Text to convert to binary. */ 192 int what_kind, /* 'd', 'f', 'g', 'h' */ 193 LITTLENUM_TYPE *words) /* Build the binary here. */ 194 { 195 FLONUM_TYPE f; 196 LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD]; 197 /* Extra bits for zeroed low-order bits. 198 The 1st MAX_PRECISION are zeroed, 199 the last contain flonum bits. */ 200 char *return_value; 201 int precision; /* Number of 16-bit words in the format. */ 202 long exponent_bits; 203 204 return_value = str; 205 f.low = bits + MAX_PRECISION; 206 f.high = NULL; 207 f.leader = NULL; 208 f.exponent = 0; 209 f.sign = '\0'; 210 211 if (what_kind_of_float (what_kind, &precision, &exponent_bits)) 212 { 213 return_value = NULL; 214 make_invalid_floating_point_number (words); 215 } 216 217 if (return_value) 218 { 219 memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION); 220 221 /* Use more LittleNums than seems 222 necessary: the highest flonum may have 223 15 leading 0 bits, so could be useless. */ 224 f.high = f.low + precision - 1 + GUARD; 225 226 if (atof_generic (&return_value, ".", "eE", &f)) 227 { 228 make_invalid_floating_point_number (words); 229 return_value = NULL; 230 } 231 else if (flonum_gen2vax (what_kind, &f, words)) 232 return_value = NULL; 233 } 234 235 return return_value; 236 } 237 238 /* In: a flonum, a vax floating point format. 239 Out: a vax floating-point bit pattern. */ 240 241 int 242 flonum_gen2vax (int format_letter, /* One of 'd' 'f' 'g' 'h'. */ 243 FLONUM_TYPE *f, 244 LITTLENUM_TYPE *words) /* Deliver answer here. */ 245 { 246 LITTLENUM_TYPE *lp; 247 int precision; 248 long exponent_bits; 249 int return_value; /* 0 == OK. */ 250 251 return_value = what_kind_of_float (format_letter, &precision, &exponent_bits); 252 253 if (return_value != 0) 254 make_invalid_floating_point_number (words); 255 256 else 257 { 258 if (f->low > f->leader) 259 /* 0.0e0 seen. */ 260 memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision); 261 262 else 263 { 264 long exponent_1; 265 long exponent_2; 266 long exponent_3; 267 long exponent_4; 268 int exponent_skippage; 269 LITTLENUM_TYPE word1; 270 271 if (f->sign != '-' && f->sign != '+') 272 { 273 if (f->sign == 0) 274 { 275 /* All NaNs are 0. */ 276 memset (words, 0x00, sizeof (LITTLENUM_TYPE) * precision); 277 } 278 else if (f->sign == 'P') 279 { 280 /* Positive Infinity. */ 281 memset (words, 0xff, sizeof (LITTLENUM_TYPE) * precision); 282 words[0] &= 0x7fff; 283 } 284 else if (f->sign == 'N') 285 { 286 /* Negative Infinity. */ 287 memset (words, 0x00, sizeof (LITTLENUM_TYPE) * precision); 288 words[0] = 0x0080; 289 } 290 else 291 make_invalid_floating_point_number (words); 292 return return_value; 293 } 294 295 /* All vaxen floating_point formats (so far) have: 296 Bit 15 is sign bit. 297 Bits 14:n are excess-whatever exponent. 298 Bits n-1:0 (if any) are most significant bits of fraction. 299 Bits 15:0 of the next word are the next most significant bits. 300 And so on for each other word. 301 302 All this to be compatible with a KF11?? (Which is still faster 303 than lots of vaxen I can think of, but it also has higher 304 maintenance costs ... sigh). 305 306 So we need: number of bits of exponent, number of bits of 307 mantissa. */ 308 309 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS; 310 littlenum_pointer = f->leader; 311 littlenum_end = f->low; 312 /* Seek (and forget) 1st significant bit. */ 313 for (exponent_skippage = 0; 314 !next_bits (1); 315 exponent_skippage++);; 316 317 exponent_1 = f->exponent + f->leader + 1 - f->low; 318 /* Radix LITTLENUM_RADIX, point just higher than f->leader. */ 319 exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS; 320 /* Radix 2. */ 321 exponent_3 = exponent_2 - exponent_skippage; 322 /* Forget leading zeros, forget 1st bit. */ 323 exponent_4 = exponent_3 + (1 << (exponent_bits - 1)); 324 /* Offset exponent. */ 325 326 if (exponent_4 & ~mask[exponent_bits]) 327 { 328 /* Exponent overflow. Lose immediately. */ 329 make_invalid_floating_point_number (words); 330 331 /* We leave return_value alone: admit we read the 332 number, but return a floating exception 333 because we can't encode the number. */ 334 } 335 else 336 { 337 lp = words; 338 339 /* Word 1. Sign, exponent and perhaps high bits. 340 Assume 2's complement integers. */ 341 word1 = (((exponent_4 & mask[exponent_bits]) << (15 - exponent_bits)) 342 | ((f->sign == '+') ? 0 : 0x8000) 343 | next_bits (15 - exponent_bits)); 344 *lp++ = word1; 345 346 /* The rest of the words are just mantissa bits. */ 347 for (; lp < words + precision; lp++) 348 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS); 349 350 if (next_bits (1)) 351 { 352 /* Since the NEXT bit is a 1, round UP the mantissa. 353 The cunning design of these hidden-1 floats permits 354 us to let the mantissa overflow into the exponent, and 355 it 'does the right thing'. However, we lose if the 356 highest-order bit of the lowest-order word flips. 357 Is that clear? */ 358 unsigned long carry; 359 360 /* 361 #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2) 362 Please allow at least 1 more bit in carry than is in a LITTLENUM. 363 We need that extra bit to hold a carry during a LITTLENUM carry 364 propagation. Another extra bit (kept 0) will assure us that we 365 don't get a sticky sign bit after shifting right, and that 366 permits us to propagate the carry without any masking of bits. 367 #endif */ 368 for (carry = 1, lp--; 369 carry && (lp >= words); 370 lp--) 371 { 372 carry = *lp + carry; 373 *lp = carry; 374 carry >>= LITTLENUM_NUMBER_OF_BITS; 375 } 376 377 if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1))) 378 { 379 make_invalid_floating_point_number (words); 380 /* We leave return_value alone: admit we read the 381 number, but return a floating exception 382 because we can't encode the number. */ 383 } 384 } 385 } 386 } 387 } 388 return return_value; 389 } 390 391 /* JF this used to be in vax.c but this looks like a better place for it. */ 392 393 /* In: input_line_pointer->the 1st character of a floating-point 394 number. 395 1 letter denoting the type of statement that wants a 396 binary floating point number returned. 397 Address of where to build floating point literal. 398 Assumed to be 'big enough'. 399 Address of where to return size of literal (in chars). 400 401 Out: Input_line_pointer->of next char after floating number. 402 Error message, or 0. 403 Floating point literal. 404 Number of chars we used for the literal. */ 405 406 #define MAXIMUM_NUMBER_OF_LITTLENUMS 8 /* For .hfloats. */ 407 408 char * 409 vax_md_atof (int what_statement_type, 410 char *literalP, 411 int *sizeP) 412 { 413 LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS]; 414 char kind_of_float; 415 unsigned int number_of_chars; 416 LITTLENUM_TYPE *littlenumP; 417 418 switch (what_statement_type) 419 { 420 case 'F': 421 case 'f': 422 kind_of_float = 'f'; 423 break; 424 425 case 'D': 426 case 'd': 427 kind_of_float = 'd'; 428 break; 429 430 case 'g': 431 kind_of_float = 'g'; 432 break; 433 434 case 'h': 435 kind_of_float = 'h'; 436 break; 437 438 default: 439 kind_of_float = 0; 440 break; 441 }; 442 443 if (kind_of_float) 444 { 445 LITTLENUM_TYPE *limit; 446 447 input_line_pointer = atof_vax (input_line_pointer, 448 kind_of_float, 449 words); 450 /* The atof_vax() builds up 16-bit numbers. 451 Since the assembler may not be running on 452 a little-endian machine, be very careful about 453 converting words to chars. */ 454 number_of_chars = atof_vax_sizeof (kind_of_float); 455 know (number_of_chars <= MAXIMUM_NUMBER_OF_LITTLENUMS * sizeof (LITTLENUM_TYPE)); 456 limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE)); 457 for (littlenumP = words; littlenumP < limit; littlenumP++) 458 { 459 md_number_to_chars (literalP, *littlenumP, sizeof (LITTLENUM_TYPE)); 460 literalP += sizeof (LITTLENUM_TYPE); 461 }; 462 } 463 else 464 number_of_chars = 0; 465 466 *sizeP = number_of_chars; 467 return kind_of_float ? NULL : _("Unrecognized or unsupported floating point constant"); 468 } 469