1 /* atof_vax.c - turn a Flonum into a VAX floating point number
2 Copyright 1987, 1992, 1993, 1995, 1997, 1999, 2000, 2005
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 2, 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 int
atof_vax_sizeof(int letter)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
next_bits(int number_of_bits)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
make_invalid_floating_point_number(LITTLENUM_TYPE * words)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. */
what_kind_of_float(int letter,int * precisionP,long * exponent_bitsP)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 *
atof_vax(char * str,int what_kind,LITTLENUM_TYPE * words)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
flonum_gen2vax(int format_letter,FLONUM_TYPE * f,LITTLENUM_TYPE * words)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 /* JF: Deal with new Nan, +Inf and -Inf codes. */
272 if (f->sign != '-' && f->sign != '+')
273 {
274 make_invalid_floating_point_number (words);
275 return return_value;
276 }
277
278 /* All vaxen floating_point formats (so far) have:
279 Bit 15 is sign bit.
280 Bits 14:n are excess-whatever exponent.
281 Bits n-1:0 (if any) are most significant bits of fraction.
282 Bits 15:0 of the next word are the next most significant bits.
283 And so on for each other word.
284
285 All this to be compatible with a KF11?? (Which is still faster
286 than lots of vaxen I can think of, but it also has higher
287 maintenance costs ... sigh).
288
289 So we need: number of bits of exponent, number of bits of
290 mantissa. */
291
292 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
293 littlenum_pointer = f->leader;
294 littlenum_end = f->low;
295 /* Seek (and forget) 1st significant bit. */
296 for (exponent_skippage = 0;
297 !next_bits (1);
298 exponent_skippage++);;
299
300 exponent_1 = f->exponent + f->leader + 1 - f->low;
301 /* Radix LITTLENUM_RADIX, point just higher than f->leader. */
302 exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
303 /* Radix 2. */
304 exponent_3 = exponent_2 - exponent_skippage;
305 /* Forget leading zeros, forget 1st bit. */
306 exponent_4 = exponent_3 + (1 << (exponent_bits - 1));
307 /* Offset exponent. */
308
309 if (exponent_4 & ~mask[exponent_bits])
310 {
311 /* Exponent overflow. Lose immediately. */
312 make_invalid_floating_point_number (words);
313
314 /* We leave return_value alone: admit we read the
315 number, but return a floating exception
316 because we can't encode the number. */
317 }
318 else
319 {
320 lp = words;
321
322 /* Word 1. Sign, exponent and perhaps high bits.
323 Assume 2's complement integers. */
324 word1 = (((exponent_4 & mask[exponent_bits]) << (15 - exponent_bits))
325 | ((f->sign == '+') ? 0 : 0x8000)
326 | next_bits (15 - exponent_bits));
327 *lp++ = word1;
328
329 /* The rest of the words are just mantissa bits. */
330 for (; lp < words + precision; lp++)
331 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
332
333 if (next_bits (1))
334 {
335 /* Since the NEXT bit is a 1, round UP the mantissa.
336 The cunning design of these hidden-1 floats permits
337 us to let the mantissa overflow into the exponent, and
338 it 'does the right thing'. However, we lose if the
339 highest-order bit of the lowest-order word flips.
340 Is that clear? */
341 unsigned long carry;
342
343 /*
344 #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
345 Please allow at least 1 more bit in carry than is in a LITTLENUM.
346 We need that extra bit to hold a carry during a LITTLENUM carry
347 propagation. Another extra bit (kept 0) will assure us that we
348 don't get a sticky sign bit after shifting right, and that
349 permits us to propagate the carry without any masking of bits.
350 #endif */
351 for (carry = 1, lp--;
352 carry && (lp >= words);
353 lp--)
354 {
355 carry = *lp + carry;
356 *lp = carry;
357 carry >>= LITTLENUM_NUMBER_OF_BITS;
358 }
359
360 if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
361 {
362 make_invalid_floating_point_number (words);
363 /* We leave return_value alone: admit we read the
364 number, but return a floating exception
365 because we can't encode the number. */
366 }
367 }
368 }
369 }
370 }
371 return return_value;
372 }
373
374 /* JF this used to be in vax.c but this looks like a better place for it. */
375
376 /* In: input_line_pointer->the 1st character of a floating-point
377 number.
378 1 letter denoting the type of statement that wants a
379 binary floating point number returned.
380 Address of where to build floating point literal.
381 Assumed to be 'big enough'.
382 Address of where to return size of literal (in chars).
383
384 Out: Input_line_pointer->of next char after floating number.
385 Error message, or 0.
386 Floating point literal.
387 Number of chars we used for the literal. */
388
389 #define MAXIMUM_NUMBER_OF_LITTLENUMS 8 /* For .hfloats. */
390
391 char *
md_atof(int what_statement_type,char * literalP,int * sizeP)392 md_atof (int what_statement_type,
393 char *literalP,
394 int *sizeP)
395 {
396 LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS];
397 char kind_of_float;
398 int number_of_chars;
399 LITTLENUM_TYPE *littlenumP;
400
401 switch (what_statement_type)
402 {
403 case 'F':
404 case 'f':
405 kind_of_float = 'f';
406 break;
407
408 case 'D':
409 case 'd':
410 kind_of_float = 'd';
411 break;
412
413 case 'g':
414 kind_of_float = 'g';
415 break;
416
417 case 'h':
418 kind_of_float = 'h';
419 break;
420
421 default:
422 kind_of_float = 0;
423 break;
424 };
425
426 if (kind_of_float)
427 {
428 LITTLENUM_TYPE *limit;
429
430 input_line_pointer = atof_vax (input_line_pointer,
431 kind_of_float,
432 words);
433 /* The atof_vax() builds up 16-bit numbers.
434 Since the assembler may not be running on
435 a little-endian machine, be very careful about
436 converting words to chars. */
437 number_of_chars = atof_vax_sizeof (kind_of_float);
438 know (number_of_chars <= MAXIMUM_NUMBER_OF_LITTLENUMS * sizeof (LITTLENUM_TYPE));
439 limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
440 for (littlenumP = words; littlenumP < limit; littlenumP++)
441 {
442 md_number_to_chars (literalP, *littlenumP, sizeof (LITTLENUM_TYPE));
443 literalP += sizeof (LITTLENUM_TYPE);
444 };
445 }
446 else
447 number_of_chars = 0;
448
449 *sizeP = number_of_chars;
450 return kind_of_float ? NULL : _("Bad call to md_atof()");
451 }
452