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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
49int
50sgl_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}
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