1 /* atof_vax.c - turn a Flonum into a VAX floating point number
2 Copyright (C) 1987-2023 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
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
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
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
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 }