source: trunk/binutils/gas/config/atof-tahoe.c@ 3935

Last change on this file since 3935 was 10, checked in by bird, 23 years ago

Initial revision
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Line 
1/* atof_tahoe.c - turn a string into a Tahoe floating point number
2 Copyright 1987, 1993, 2000 Free Software Foundation, Inc.
3
4/* This is really a simplified version of atof_vax.c. I glommed it wholesale
5 and then shaved it down. I don't even know how it works. (Don't you find
6 my honesty refreshing? Devon E Bowen <bowen@cs.buffalo.edu>
7
8 I don't allow uppercase letters in the precision descrpitors.
9 i.e. 'f' and 'd' are allowed but 'F' and 'D' aren't. */
10
11#include "as.h"
12
13/* Precision in LittleNums. */
14#define MAX_PRECISION (4)
15#define D_PRECISION (4)
16#define F_PRECISION (2)
17
18/* Precision in chars. */
19#define D_PRECISION_CHARS (8)
20#define F_PRECISION_CHARS (4)
21
22/* Length in LittleNums of guard bits. */
23#define GUARD (2)
24
25static const long int mask[] =
26{
27 0x00000000,
28 0x00000001,
29 0x00000003,
30 0x00000007,
31 0x0000000f,
32 0x0000001f,
33 0x0000003f,
34 0x0000007f,
35 0x000000ff,
36 0x000001ff,
37 0x000003ff,
38 0x000007ff,
39 0x00000fff,
40 0x00001fff,
41 0x00003fff,
42 0x00007fff,
43 0x0000ffff,
44 0x0001ffff,
45 0x0003ffff,
46 0x0007ffff,
47 0x000fffff,
48 0x001fffff,
49 0x003fffff,
50 0x007fffff,
51 0x00ffffff,
52 0x01ffffff,
53 0x03ffffff,
54 0x07ffffff,
55 0x0fffffff,
56 0x1fffffff,
57 0x3fffffff,
58 0x7fffffff,
59 0xffffffff
60};
61
62
63/* Shared between flonum_gen2tahoe and next_bits. */
64static int bits_left_in_littlenum;
65static LITTLENUM_TYPE *littlenum_pointer;
66static LITTLENUM_TYPE *littlenum_end;
67
68#if __STDC__ == 1
69
70int flonum_gen2tahoe (int format_letter, FLONUM_TYPE * f,
71 LITTLENUM_TYPE * words);
72
73#else /* not __STDC__ */
74
75int flonum_gen2tahoe ();
76
77#endif /* not __STDC__ */
78
79static int
80next_bits (number_of_bits)
81 int number_of_bits;
82{
83 int return_value;
84
85 if (littlenum_pointer < littlenum_end)
86 return 0;
87 if (number_of_bits >= bits_left_in_littlenum)
88 {
89 return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
90 number_of_bits -= bits_left_in_littlenum;
91 return_value <<= number_of_bits;
92 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
93 littlenum_pointer--;
94 if (littlenum_pointer >= littlenum_end)
95 return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) &
96 mask[number_of_bits];
97 }
98 else
99 {
100 bits_left_in_littlenum -= number_of_bits;
101 return_value = mask[number_of_bits] &
102 ((*littlenum_pointer) >> bits_left_in_littlenum);
103 }
104 return return_value;
105}
106
107static void
108make_invalid_floating_point_number (words)
109 LITTLENUM_TYPE *words;
110{
111 /* Floating Reserved Operand Code. */
112 *words = 0x8000;
113}
114
115
116static int /* 0 means letter is OK. */
117what_kind_of_float (letter, precisionP, exponent_bitsP)
118 /* In: lowercase please. What kind of float? */
119 char letter;
120
121 /* Number of 16-bit words in the float. */
122 int *precisionP;
123
124 /* Number of exponent bits. */
125 long int *exponent_bitsP;
126{
127 int retval; /* 0: OK. */
128
129 retval = 0;
130 switch (letter)
131 {
132 case 'f':
133 *precisionP = F_PRECISION;
134 *exponent_bitsP = 8;
135 break;
136
137 case 'd':
138 *precisionP = D_PRECISION;
139 *exponent_bitsP = 8;
140 break;
141
142 default:
143 retval = 69;
144 break;
145 }
146 return (retval);
147}
148
149
150/* Warning: This returns 16-bit LITTLENUMs, because that is what the
151 VAX thinks in. It is up to the caller to figure out any alignment
152 problems and to conspire for the bytes/word to be emitted in the
153 right order. Bigendians beware! */
154
155char * /* Return pointer past text consumed. */
156atof_tahoe (str, what_kind, words)
157 char *str; /* Text to convert to binary. */
158 char what_kind; /* 'd', 'f', 'g', 'h' */
159 LITTLENUM_TYPE *words; /* Build the binary here. */
160{
161 FLONUM_TYPE f;
162 LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
163 /* Extra bits for zeroed low-order bits. */
164 /* The 1st MAX_PRECISION are zeroed, the last contain flonum bits. */
165 char *return_value;
166 int precision; /* Number of 16-bit words in the format. */
167 long int exponent_bits;
168
169 return_value = str;
170 f.low = bits + MAX_PRECISION;
171 f.high = NULL;
172 f.leader = NULL;
173 f.exponent = NULL;
174 f.sign = '\0';
175
176 if (what_kind_of_float (what_kind, &precision, &exponent_bits))
177 {
178 /* We lost. */
179 return_value = NULL;
180 make_invalid_floating_point_number (words);
181 }
182 if (return_value)
183 {
184 memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);
185
186 /* Use more LittleNums than seems necessary:
187 the highest flonum may have 15 leading 0 bits, so could be
188 useless. */
189 f.high = f.low + precision - 1 + GUARD;
190
191 if (atof_generic (&return_value, ".", "eE", &f))
192 {
193 make_invalid_floating_point_number (words);
194 /* We lost. */
195 return_value = NULL;
196 }
197 else
198 {
199 if (flonum_gen2tahoe (what_kind, &f, words))
200 return_value = NULL;
201 }
202 }
203 return return_value;
204}
205
206
207/* In: a flonum, a Tahoe floating point format.
208 Out: a Tahoe floating-point bit pattern. */
209
210int /* 0: OK. */
211flonum_gen2tahoe (format_letter, f, words)
212 char format_letter; /* One of 'd' 'f'. */
213 FLONUM_TYPE *f;
214 LITTLENUM_TYPE *words; /* Deliver answer here. */
215{
216 LITTLENUM_TYPE *lp;
217 int precision;
218 long int exponent_bits;
219 int return_value; /* 0 == OK. */
220
221 return_value =
222 what_kind_of_float (format_letter, &precision, &exponent_bits);
223 if (return_value != 0)
224 {
225 make_invalid_floating_point_number (words);
226 }
227 else
228 {
229 if (f->low > f->leader)
230 {
231 /* 0.0e0 seen. */
232 memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision);
233 }
234 else
235 {
236 long int exponent_1;
237 long int exponent_2;
238 long int exponent_3;
239 long int exponent_4;
240 int exponent_skippage;
241 LITTLENUM_TYPE word1;
242
243 /* JF: Deal with new Nan, +Inf and -Inf codes. */
244 if (f->sign != '-' && f->sign != '+')
245 {
246 make_invalid_floating_point_number (words);
247 return return_value;
248 }
249 /* All tahoe floating_point formats have:
250 Bit 15 is sign bit.
251 Bits 14:n are excess-whatever exponent.
252 Bits n-1:0 (if any) are most significant bits of fraction.
253 Bits 15:0 of the next word are the next most significant bits.
254 And so on for each other word.
255
256 So we need: number of bits of exponent, number of bits of
257 mantissa. */
258
259 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
260 littlenum_pointer = f->leader;
261 littlenum_end = f->low;
262
263 /* Seek (and forget) 1st significant bit. */
264 for (exponent_skippage = 0;
265 !next_bits (1);
266 exponent_skippage++)
267 ;
268
269 exponent_1 = f->exponent + f->leader + 1 - f->low;
270
271 /* Radix LITTLENUM_RADIX, point just higher than f -> leader. */
272 exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
273
274 /* Radix 2. */
275 exponent_3 = exponent_2 - exponent_skippage;
276
277 /* Forget leading zeros, forget 1st bit. */
278 exponent_4 = exponent_3 + (1 << (exponent_bits - 1));
279
280 /* Offset exponent. */
281
282 if (exponent_4 & ~mask[exponent_bits])
283 {
284 /* Exponent overflow. Lose immediately. */
285
286 make_invalid_floating_point_number (words);
287
288 /* We leave return_value alone: admit we read the
289 number, but return a floating exception because we
290 can't encode the number. */
291 }
292 else
293 {
294 lp = words;
295
296 /* Word 1. Sign, exponent and perhaps high bits. */
297 /* Assume 2's complement integers. */
298 word1 = ((exponent_4 & mask[exponent_bits])
299 << (15 - exponent_bits))
300 | ((f->sign == '+') ? 0 : 0x8000)
301 | next_bits (15 - exponent_bits);
302 *lp++ = word1;
303
304 /* The rest of the words are just mantissa bits. */
305 for (; lp < words + precision; lp++)
306 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
307
308 if (next_bits (1))
309 {
310 /* Since the NEXT bit is a 1, round UP the mantissa.
311 The cunning design of these hidden-1 floats permits
312 us to let the mantissa overflow into the exponent, and
313 it 'does the right thing'. However, we lose if the
314 highest-order bit of the lowest-order word flips.
315 Is that clear? */
316
317 unsigned long int carry;
318
319 /* #if (sizeof(carry)) < ((sizeof(bits[0]) *
320 BITS_PER_CHAR) + 2) Please allow at least 1 more
321 bit in carry than is in a LITTLENUM. We need
322 that extra bit to hold a carry during a LITTLENUM
323 carry propagation. Another extra bit (kept 0)
324 will assure us that we don't get a sticky sign
325 bit after shifting right, and that permits us to
326 propagate the carry without any masking of bits.
327 #endif */
328 for (carry = 1, lp--;
329 carry && (lp >= words);
330 lp--)
331 {
332 carry = *lp + carry;
333 *lp = carry;
334 carry >>= LITTLENUM_NUMBER_OF_BITS;
335 }
336
337 if ((word1 ^ *words)
338 & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
339 {
340 make_invalid_floating_point_number (words);
341 /* We leave return_value alone: admit we read
342 the number, but return a floating exception
343 because we can't encode the number. */
344 }
345 } /* if (we needed to round up) */
346 } /* if (exponent overflow) */
347 } /* if (0.0e0) */
348 } /* if (float_type was OK) */
349 return return_value;
350}
351
352
353/* In: input_line_pointer -> the 1st character of a floating-point
354 * number.
355 * 1 letter denoting the type of statement that wants a
356 * binary floating point number returned.
357 * Address of where to build floating point literal.
358 * Assumed to be 'big enough'.
359 * Address of where to return size of literal (in chars).
360 *
361 * Out: Input_line_pointer -> of next char after floating number.
362 * Error message, or 0.
363 * Floating point literal.
364 * Number of chars we used for the literal. */
365
366char *
367md_atof (what_statement_type, literalP, sizeP)
368 char what_statement_type;
369 char *literalP;
370 int *sizeP;
371{
372 LITTLENUM_TYPE words[MAX_PRECISION];
373 register char kind_of_float;
374 register int number_of_chars;
375 register LITTLENUM_TYPE *littlenum_pointer;
376
377 switch (what_statement_type)
378 {
379 case 'f': /* .ffloat */
380 case 'd': /* .dfloat */
381 kind_of_float = what_statement_type;
382 break;
383
384 default:
385 kind_of_float = 0;
386 break;
387 }
388
389 if (kind_of_float)
390 {
391 register LITTLENUM_TYPE *limit;
392
393 input_line_pointer = atof_tahoe (input_line_pointer,
394 kind_of_float,
395 words);
396 /* The atof_tahoe() builds up 16-bit numbers.
397 Since the assembler may not be running on
398 a different-endian machine, be very careful about
399 converting words to chars. */
400 number_of_chars = (kind_of_float == 'f' ? F_PRECISION_CHARS :
401 (kind_of_float == 'd' ? D_PRECISION_CHARS : 0));
402 know (number_of_chars <= MAX_PRECISION * sizeof (LITTLENUM_TYPE));
403 limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
404 for (littlenum_pointer = words;
405 littlenum_pointer < limit;
406 littlenum_pointer++)
407 {
408 md_number_to_chars (literalP, *littlenum_pointer,
409 sizeof (LITTLENUM_TYPE));
410 literalP += sizeof (LITTLENUM_TYPE);
411 }
412 }
413 else
414 {
415 number_of_chars = 0;
416 }
417
418 *sizeP = number_of_chars;
419 return kind_of_float ? 0 : _("Bad call to md_atof()");
420}
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