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1da177e4 LT |
1 | /* |
2 | * Linux/PA-RISC Project (http://www.parisc-linux.org/) | |
3 | * | |
4 | * Floating-point emulation code | |
5 | * Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org> | |
6 | * | |
7 | * This program 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 | * This program 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 this program; if not, write to the Free Software | |
19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
20 | */ | |
21 | /* | |
22 | * BEGIN_DESC | |
23 | * | |
24 | * File: | |
25 | * @(#) pa/spmath/sfdiv.c $Revision: 1.1 $ | |
26 | * | |
27 | * Purpose: | |
28 | * Single Precision Floating-point Divide | |
29 | * | |
30 | * External Interfaces: | |
31 | * sgl_fdiv(srcptr1,srcptr2,dstptr,status) | |
32 | * | |
33 | * Internal Interfaces: | |
34 | * | |
35 | * Theory: | |
36 | * <<please update with a overview of the operation of this file>> | |
37 | * | |
38 | * END_DESC | |
39 | */ | |
40 | ||
41 | ||
42 | #include "float.h" | |
43 | #include "sgl_float.h" | |
44 | ||
45 | /* | |
46 | * Single Precision Floating-point Divide | |
47 | */ | |
48 | ||
49 | int | |
50 | sgl_fdiv (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2, | |
51 | sgl_floating_point * dstptr, unsigned int *status) | |
52 | { | |
53 | register unsigned int opnd1, opnd2, opnd3, result; | |
54 | register int dest_exponent, count; | |
55 | register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE; | |
56 | boolean is_tiny; | |
57 | ||
58 | opnd1 = *srcptr1; | |
59 | opnd2 = *srcptr2; | |
60 | /* | |
61 | * set sign bit of result | |
62 | */ | |
63 | if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result); | |
64 | else Sgl_setzero(result); | |
65 | /* | |
66 | * check first operand for NaN's or infinity | |
67 | */ | |
68 | if (Sgl_isinfinity_exponent(opnd1)) { | |
69 | if (Sgl_iszero_mantissa(opnd1)) { | |
70 | if (Sgl_isnotnan(opnd2)) { | |
71 | if (Sgl_isinfinity(opnd2)) { | |
72 | /* | |
73 | * invalid since both operands | |
74 | * are infinity | |
75 | */ | |
76 | if (Is_invalidtrap_enabled()) | |
77 | return(INVALIDEXCEPTION); | |
78 | Set_invalidflag(); | |
79 | Sgl_makequietnan(result); | |
80 | *dstptr = result; | |
81 | return(NOEXCEPTION); | |
82 | } | |
83 | /* | |
84 | * return infinity | |
85 | */ | |
86 | Sgl_setinfinity_exponentmantissa(result); | |
87 | *dstptr = result; | |
88 | return(NOEXCEPTION); | |
89 | } | |
90 | } | |
91 | else { | |
92 | /* | |
93 | * is NaN; signaling or quiet? | |
94 | */ | |
95 | if (Sgl_isone_signaling(opnd1)) { | |
96 | /* trap if INVALIDTRAP enabled */ | |
97 | if (Is_invalidtrap_enabled()) | |
98 | return(INVALIDEXCEPTION); | |
99 | /* make NaN quiet */ | |
100 | Set_invalidflag(); | |
101 | Sgl_set_quiet(opnd1); | |
102 | } | |
103 | /* | |
104 | * is second operand a signaling NaN? | |
105 | */ | |
106 | else if (Sgl_is_signalingnan(opnd2)) { | |
107 | /* trap if INVALIDTRAP enabled */ | |
108 | if (Is_invalidtrap_enabled()) | |
109 | return(INVALIDEXCEPTION); | |
110 | /* make NaN quiet */ | |
111 | Set_invalidflag(); | |
112 | Sgl_set_quiet(opnd2); | |
113 | *dstptr = opnd2; | |
114 | return(NOEXCEPTION); | |
115 | } | |
116 | /* | |
117 | * return quiet NaN | |
118 | */ | |
119 | *dstptr = opnd1; | |
120 | return(NOEXCEPTION); | |
121 | } | |
122 | } | |
123 | /* | |
124 | * check second operand for NaN's or infinity | |
125 | */ | |
126 | if (Sgl_isinfinity_exponent(opnd2)) { | |
127 | if (Sgl_iszero_mantissa(opnd2)) { | |
128 | /* | |
129 | * return zero | |
130 | */ | |
131 | Sgl_setzero_exponentmantissa(result); | |
132 | *dstptr = result; | |
133 | return(NOEXCEPTION); | |
134 | } | |
135 | /* | |
136 | * is NaN; signaling or quiet? | |
137 | */ | |
138 | if (Sgl_isone_signaling(opnd2)) { | |
139 | /* trap if INVALIDTRAP enabled */ | |
140 | if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION); | |
141 | /* make NaN quiet */ | |
142 | Set_invalidflag(); | |
143 | Sgl_set_quiet(opnd2); | |
144 | } | |
145 | /* | |
146 | * return quiet NaN | |
147 | */ | |
148 | *dstptr = opnd2; | |
149 | return(NOEXCEPTION); | |
150 | } | |
151 | /* | |
152 | * check for division by zero | |
153 | */ | |
154 | if (Sgl_iszero_exponentmantissa(opnd2)) { | |
155 | if (Sgl_iszero_exponentmantissa(opnd1)) { | |
156 | /* invalid since both operands are zero */ | |
157 | if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION); | |
158 | Set_invalidflag(); | |
159 | Sgl_makequietnan(result); | |
160 | *dstptr = result; | |
161 | return(NOEXCEPTION); | |
162 | } | |
163 | if (Is_divisionbyzerotrap_enabled()) | |
164 | return(DIVISIONBYZEROEXCEPTION); | |
165 | Set_divisionbyzeroflag(); | |
166 | Sgl_setinfinity_exponentmantissa(result); | |
167 | *dstptr = result; | |
168 | return(NOEXCEPTION); | |
169 | } | |
170 | /* | |
171 | * Generate exponent | |
172 | */ | |
173 | dest_exponent = Sgl_exponent(opnd1) - Sgl_exponent(opnd2) + SGL_BIAS; | |
174 | ||
175 | /* | |
176 | * Generate mantissa | |
177 | */ | |
178 | if (Sgl_isnotzero_exponent(opnd1)) { | |
179 | /* set hidden bit */ | |
180 | Sgl_clear_signexponent_set_hidden(opnd1); | |
181 | } | |
182 | else { | |
183 | /* check for zero */ | |
184 | if (Sgl_iszero_mantissa(opnd1)) { | |
185 | Sgl_setzero_exponentmantissa(result); | |
186 | *dstptr = result; | |
187 | return(NOEXCEPTION); | |
188 | } | |
189 | /* is denormalized; want to normalize */ | |
190 | Sgl_clear_signexponent(opnd1); | |
191 | Sgl_leftshiftby1(opnd1); | |
192 | Sgl_normalize(opnd1,dest_exponent); | |
193 | } | |
194 | /* opnd2 needs to have hidden bit set with msb in hidden bit */ | |
195 | if (Sgl_isnotzero_exponent(opnd2)) { | |
196 | Sgl_clear_signexponent_set_hidden(opnd2); | |
197 | } | |
198 | else { | |
199 | /* is denormalized; want to normalize */ | |
200 | Sgl_clear_signexponent(opnd2); | |
201 | Sgl_leftshiftby1(opnd2); | |
202 | while(Sgl_iszero_hiddenhigh7mantissa(opnd2)) { | |
203 | Sgl_leftshiftby8(opnd2); | |
204 | dest_exponent += 8; | |
205 | } | |
206 | if(Sgl_iszero_hiddenhigh3mantissa(opnd2)) { | |
207 | Sgl_leftshiftby4(opnd2); | |
208 | dest_exponent += 4; | |
209 | } | |
210 | while(Sgl_iszero_hidden(opnd2)) { | |
211 | Sgl_leftshiftby1(opnd2); | |
212 | dest_exponent += 1; | |
213 | } | |
214 | } | |
215 | ||
216 | /* Divide the source mantissas */ | |
217 | ||
218 | /* | |
219 | * A non_restoring divide algorithm is used. | |
220 | */ | |
221 | Sgl_subtract(opnd1,opnd2,opnd1); | |
222 | Sgl_setzero(opnd3); | |
223 | for (count=1;count<=SGL_P && Sgl_all(opnd1);count++) { | |
224 | Sgl_leftshiftby1(opnd1); | |
225 | Sgl_leftshiftby1(opnd3); | |
226 | if (Sgl_iszero_sign(opnd1)) { | |
227 | Sgl_setone_lowmantissa(opnd3); | |
228 | Sgl_subtract(opnd1,opnd2,opnd1); | |
229 | } | |
230 | else Sgl_addition(opnd1,opnd2,opnd1); | |
231 | } | |
232 | if (count <= SGL_P) { | |
233 | Sgl_leftshiftby1(opnd3); | |
234 | Sgl_setone_lowmantissa(opnd3); | |
235 | Sgl_leftshift(opnd3,SGL_P-count); | |
236 | if (Sgl_iszero_hidden(opnd3)) { | |
237 | Sgl_leftshiftby1(opnd3); | |
238 | dest_exponent--; | |
239 | } | |
240 | } | |
241 | else { | |
242 | if (Sgl_iszero_hidden(opnd3)) { | |
243 | /* need to get one more bit of result */ | |
244 | Sgl_leftshiftby1(opnd1); | |
245 | Sgl_leftshiftby1(opnd3); | |
246 | if (Sgl_iszero_sign(opnd1)) { | |
247 | Sgl_setone_lowmantissa(opnd3); | |
248 | Sgl_subtract(opnd1,opnd2,opnd1); | |
249 | } | |
250 | else Sgl_addition(opnd1,opnd2,opnd1); | |
251 | dest_exponent--; | |
252 | } | |
253 | if (Sgl_iszero_sign(opnd1)) guardbit = TRUE; | |
254 | stickybit = Sgl_all(opnd1); | |
255 | } | |
256 | inexact = guardbit | stickybit; | |
257 | ||
258 | /* | |
259 | * round result | |
260 | */ | |
261 | if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) { | |
262 | Sgl_clear_signexponent(opnd3); | |
263 | switch (Rounding_mode()) { | |
264 | case ROUNDPLUS: | |
265 | if (Sgl_iszero_sign(result)) | |
266 | Sgl_increment_mantissa(opnd3); | |
267 | break; | |
268 | case ROUNDMINUS: | |
269 | if (Sgl_isone_sign(result)) | |
270 | Sgl_increment_mantissa(opnd3); | |
271 | break; | |
272 | case ROUNDNEAREST: | |
273 | if (guardbit) { | |
274 | if (stickybit || Sgl_isone_lowmantissa(opnd3)) | |
275 | Sgl_increment_mantissa(opnd3); | |
276 | } | |
277 | } | |
278 | if (Sgl_isone_hidden(opnd3)) dest_exponent++; | |
279 | } | |
280 | Sgl_set_mantissa(result,opnd3); | |
281 | ||
282 | /* | |
283 | * Test for overflow | |
284 | */ | |
285 | if (dest_exponent >= SGL_INFINITY_EXPONENT) { | |
286 | /* trap if OVERFLOWTRAP enabled */ | |
287 | if (Is_overflowtrap_enabled()) { | |
288 | /* | |
289 | * Adjust bias of result | |
290 | */ | |
291 | Sgl_setwrapped_exponent(result,dest_exponent,ovfl); | |
292 | *dstptr = result; | |
293 | if (inexact) | |
294 | if (Is_inexacttrap_enabled()) | |
295 | return(OVERFLOWEXCEPTION | INEXACTEXCEPTION); | |
296 | else Set_inexactflag(); | |
297 | return(OVERFLOWEXCEPTION); | |
298 | } | |
299 | Set_overflowflag(); | |
300 | /* set result to infinity or largest number */ | |
301 | Sgl_setoverflow(result); | |
302 | inexact = TRUE; | |
303 | } | |
304 | /* | |
305 | * Test for underflow | |
306 | */ | |
307 | else if (dest_exponent <= 0) { | |
308 | /* trap if UNDERFLOWTRAP enabled */ | |
309 | if (Is_underflowtrap_enabled()) { | |
310 | /* | |
311 | * Adjust bias of result | |
312 | */ | |
313 | Sgl_setwrapped_exponent(result,dest_exponent,unfl); | |
314 | *dstptr = result; | |
315 | if (inexact) | |
316 | if (Is_inexacttrap_enabled()) | |
317 | return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION); | |
318 | else Set_inexactflag(); | |
319 | return(UNDERFLOWEXCEPTION); | |
320 | } | |
321 | ||
322 | /* Determine if should set underflow flag */ | |
323 | is_tiny = TRUE; | |
324 | if (dest_exponent == 0 && inexact) { | |
325 | switch (Rounding_mode()) { | |
326 | case ROUNDPLUS: | |
327 | if (Sgl_iszero_sign(result)) { | |
328 | Sgl_increment(opnd3); | |
329 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
330 | is_tiny = FALSE; | |
331 | Sgl_decrement(opnd3); | |
332 | } | |
333 | break; | |
334 | case ROUNDMINUS: | |
335 | if (Sgl_isone_sign(result)) { | |
336 | Sgl_increment(opnd3); | |
337 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
338 | is_tiny = FALSE; | |
339 | Sgl_decrement(opnd3); | |
340 | } | |
341 | break; | |
342 | case ROUNDNEAREST: | |
343 | if (guardbit && (stickybit || | |
344 | Sgl_isone_lowmantissa(opnd3))) { | |
345 | Sgl_increment(opnd3); | |
346 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
347 | is_tiny = FALSE; | |
348 | Sgl_decrement(opnd3); | |
349 | } | |
350 | break; | |
351 | } | |
352 | } | |
353 | ||
354 | /* | |
355 | * denormalize result or set to signed zero | |
356 | */ | |
357 | stickybit = inexact; | |
358 | Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact); | |
359 | ||
360 | /* return rounded number */ | |
361 | if (inexact) { | |
362 | switch (Rounding_mode()) { | |
363 | case ROUNDPLUS: | |
364 | if (Sgl_iszero_sign(result)) { | |
365 | Sgl_increment(opnd3); | |
366 | } | |
367 | break; | |
368 | case ROUNDMINUS: | |
369 | if (Sgl_isone_sign(result)) { | |
370 | Sgl_increment(opnd3); | |
371 | } | |
372 | break; | |
373 | case ROUNDNEAREST: | |
374 | if (guardbit && (stickybit || | |
375 | Sgl_isone_lowmantissa(opnd3))) { | |
376 | Sgl_increment(opnd3); | |
377 | } | |
378 | break; | |
379 | } | |
380 | if (is_tiny) Set_underflowflag(); | |
381 | } | |
382 | Sgl_set_exponentmantissa(result,opnd3); | |
383 | } | |
384 | else Sgl_set_exponent(result,dest_exponent); | |
385 | *dstptr = result; | |
386 | /* check for inexact */ | |
387 | if (inexact) { | |
388 | if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION); | |
389 | else Set_inexactflag(); | |
390 | } | |
391 | return(NOEXCEPTION); | |
392 | } |