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review.evervolv.com / android_kernel_htc_msm8960 / 4feb8f8f4589d1cb1594e344c9672ec40f627ab4 / . / arch / parisc / math-emu / dfdiv.c
blob: d7d4bec0e76fd8b8a8afa77f39cae553cc906a43 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]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/dfdiv.c $Revision: 1.1 $
26 *
27 * Purpose:
28 * Double Precision Floating-point Divide
29 *
30 * External Interfaces:
31 * dbl_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 "dbl_float.h"
44
45/*
46 * Double Precision Floating-point Divide
47 */
48
49int
50dbl_fdiv (dbl_floating_point * srcptr1, dbl_floating_point * srcptr2,
51 dbl_floating_point * dstptr, unsigned int *status)
52{
53 register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
54 register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
55 register int dest_exponent, count;
56 register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
57 boolean is_tiny;
58
59 Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
60 Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
61 /*
62 * set sign bit of result
63 */
64 if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1))
65 Dbl_setnegativezerop1(resultp1);
66 else Dbl_setzerop1(resultp1);
67 /*
68 * check first operand for NaN's or infinity
69 */
70 if (Dbl_isinfinity_exponent(opnd1p1)) {
71 if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
72 if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
73 if (Dbl_isinfinity(opnd2p1,opnd2p2)) {
74 /*
75 * invalid since both operands
76 * are infinity
77 */
78 if (Is_invalidtrap_enabled())
79 return(INVALIDEXCEPTION);
80 Set_invalidflag();
81 Dbl_makequietnan(resultp1,resultp2);
82 Dbl_copytoptr(resultp1,resultp2,dstptr);
83 return(NOEXCEPTION);
84 }
85 /*
86 * return infinity
87 */
88 Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
89 Dbl_copytoptr(resultp1,resultp2,dstptr);
90 return(NOEXCEPTION);
91 }
92 }
93 else {
94 /*
95 * is NaN; signaling or quiet?
96 */
97 if (Dbl_isone_signaling(opnd1p1)) {
98 /* trap if INVALIDTRAP enabled */
99 if (Is_invalidtrap_enabled())
100 return(INVALIDEXCEPTION);
101 /* make NaN quiet */
102 Set_invalidflag();
103 Dbl_set_quiet(opnd1p1);
104 }
105 /*
106 * is second operand a signaling NaN?
107 */
108 else if (Dbl_is_signalingnan(opnd2p1)) {
109 /* trap if INVALIDTRAP enabled */
110 if (Is_invalidtrap_enabled())
111 return(INVALIDEXCEPTION);
112 /* make NaN quiet */
113 Set_invalidflag();
114 Dbl_set_quiet(opnd2p1);
115 Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
116 return(NOEXCEPTION);
117 }
118 /*
119 * return quiet NaN
120 */
121 Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
122 return(NOEXCEPTION);
123 }
124 }
125 /*
126 * check second operand for NaN's or infinity
127 */
128 if (Dbl_isinfinity_exponent(opnd2p1)) {
129 if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
130 /*
131 * return zero
132 */
133 Dbl_setzero_exponentmantissa(resultp1,resultp2);
134 Dbl_copytoptr(resultp1,resultp2,dstptr);
135 return(NOEXCEPTION);
136 }
137 /*
138 * is NaN; signaling or quiet?
139 */
140 if (Dbl_isone_signaling(opnd2p1)) {
141 /* trap if INVALIDTRAP enabled */
142 if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
143 /* make NaN quiet */
144 Set_invalidflag();
145 Dbl_set_quiet(opnd2p1);
146 }
147 /*
148 * return quiet NaN
149 */
150 Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
151 return(NOEXCEPTION);
152 }
153 /*
154 * check for division by zero
155 */
156 if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
157 if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
158 /* invalid since both operands are zero */
159 if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
160 Set_invalidflag();
161 Dbl_makequietnan(resultp1,resultp2);
162 Dbl_copytoptr(resultp1,resultp2,dstptr);
163 return(NOEXCEPTION);
164 }
165 if (Is_divisionbyzerotrap_enabled())
166 return(DIVISIONBYZEROEXCEPTION);
167 Set_divisionbyzeroflag();
168 Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
169 Dbl_copytoptr(resultp1,resultp2,dstptr);
170 return(NOEXCEPTION);
171 }
172 /*
173 * Generate exponent
174 */
175 dest_exponent = Dbl_exponent(opnd1p1) - Dbl_exponent(opnd2p1) + DBL_BIAS;
176
177 /*
178 * Generate mantissa
179 */
180 if (Dbl_isnotzero_exponent(opnd1p1)) {
181 /* set hidden bit */
182 Dbl_clear_signexponent_set_hidden(opnd1p1);
183 }
184 else {
185 /* check for zero */
186 if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
187 Dbl_setzero_exponentmantissa(resultp1,resultp2);
188 Dbl_copytoptr(resultp1,resultp2,dstptr);
189 return(NOEXCEPTION);
190 }
191 /* is denormalized, want to normalize */
192 Dbl_clear_signexponent(opnd1p1);
193 Dbl_leftshiftby1(opnd1p1,opnd1p2);
194 Dbl_normalize(opnd1p1,opnd1p2,dest_exponent);
195 }
196 /* opnd2 needs to have hidden bit set with msb in hidden bit */
197 if (Dbl_isnotzero_exponent(opnd2p1)) {
198 Dbl_clear_signexponent_set_hidden(opnd2p1);
199 }
200 else {
201 /* is denormalized; want to normalize */
202 Dbl_clear_signexponent(opnd2p1);
203 Dbl_leftshiftby1(opnd2p1,opnd2p2);
204 while (Dbl_iszero_hiddenhigh7mantissa(opnd2p1)) {
205 dest_exponent+=8;
206 Dbl_leftshiftby8(opnd2p1,opnd2p2);
207 }
208 if (Dbl_iszero_hiddenhigh3mantissa(opnd2p1)) {
209 dest_exponent+=4;
210 Dbl_leftshiftby4(opnd2p1,opnd2p2);
211 }
212 while (Dbl_iszero_hidden(opnd2p1)) {
213 dest_exponent++;
214 Dbl_leftshiftby1(opnd2p1,opnd2p2);
215 }
216 }
217
218 /* Divide the source mantissas */
219
220 /*
221 * A non-restoring divide algorithm is used.
222 */
223 Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
224 Dbl_setzero(opnd3p1,opnd3p2);
225 for (count=1; count <= DBL_P && (opnd1p1 || opnd1p2); count++) {
226 Dbl_leftshiftby1(opnd1p1,opnd1p2);
227 Dbl_leftshiftby1(opnd3p1,opnd3p2);
228 if (Dbl_iszero_sign(opnd1p1)) {
229 Dbl_setone_lowmantissap2(opnd3p2);
230 Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
231 }
232 else {
233 Twoword_add(opnd1p1, opnd1p2, opnd2p1, opnd2p2);
234 }
235 }
236 if (count <= DBL_P) {
237 Dbl_leftshiftby1(opnd3p1,opnd3p2);
238 Dbl_setone_lowmantissap2(opnd3p2);
239 Dbl_leftshift(opnd3p1,opnd3p2,(DBL_P-count));
240 if (Dbl_iszero_hidden(opnd3p1)) {
241 Dbl_leftshiftby1(opnd3p1,opnd3p2);
242 dest_exponent--;
243 }
244 }
245 else {
246 if (Dbl_iszero_hidden(opnd3p1)) {
247 /* need to get one more bit of result */
248 Dbl_leftshiftby1(opnd1p1,opnd1p2);
249 Dbl_leftshiftby1(opnd3p1,opnd3p2);
250 if (Dbl_iszero_sign(opnd1p1)) {
251 Dbl_setone_lowmantissap2(opnd3p2);
252 Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
253 }
254 else {
255 Twoword_add(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
256 }
257 dest_exponent--;
258 }
259 if (Dbl_iszero_sign(opnd1p1)) guardbit = TRUE;
260 stickybit = Dbl_allp1(opnd1p1) || Dbl_allp2(opnd1p2);
261 }
262 inexact = guardbit | stickybit;
263
264 /*
265 * round result
266 */
267 if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) {
268 Dbl_clear_signexponent(opnd3p1);
269 switch (Rounding_mode()) {
270 case ROUNDPLUS:
271 if (Dbl_iszero_sign(resultp1))
272 Dbl_increment(opnd3p1,opnd3p2);
273 break;
274 case ROUNDMINUS:
275 if (Dbl_isone_sign(resultp1))
276 Dbl_increment(opnd3p1,opnd3p2);
277 break;
278 case ROUNDNEAREST:
279 if (guardbit && (stickybit ||
280 Dbl_isone_lowmantissap2(opnd3p2))) {
281 Dbl_increment(opnd3p1,opnd3p2);
282 }
283 }
284 if (Dbl_isone_hidden(opnd3p1)) dest_exponent++;
285 }
286 Dbl_set_mantissa(resultp1,resultp2,opnd3p1,opnd3p2);
287
288 /*
289 * Test for overflow
290 */
291 if (dest_exponent >= DBL_INFINITY_EXPONENT) {
292 /* trap if OVERFLOWTRAP enabled */
293 if (Is_overflowtrap_enabled()) {
294 /*
295 * Adjust bias of result
296 */
297 Dbl_setwrapped_exponent(resultp1,dest_exponent,ovfl);
298 Dbl_copytoptr(resultp1,resultp2,dstptr);
299 if (inexact)
300 if (Is_inexacttrap_enabled())
301 return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
302 else Set_inexactflag();
303 return(OVERFLOWEXCEPTION);
304 }
305 Set_overflowflag();
306 /* set result to infinity or largest number */
307 Dbl_setoverflow(resultp1,resultp2);
308 inexact = TRUE;
309 }
310 /*
311 * Test for underflow
312 */
313 else if (dest_exponent <= 0) {
314 /* trap if UNDERFLOWTRAP enabled */
315 if (Is_underflowtrap_enabled()) {
316 /*
317 * Adjust bias of result
318 */
319 Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
320 Dbl_copytoptr(resultp1,resultp2,dstptr);
321 if (inexact)
322 if (Is_inexacttrap_enabled())
323 return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
324 else Set_inexactflag();
325 return(UNDERFLOWEXCEPTION);
326 }
327
328 /* Determine if should set underflow flag */
329 is_tiny = TRUE;
330 if (dest_exponent == 0 && inexact) {
331 switch (Rounding_mode()) {
332 case ROUNDPLUS:
333 if (Dbl_iszero_sign(resultp1)) {
334 Dbl_increment(opnd3p1,opnd3p2);
335 if (Dbl_isone_hiddenoverflow(opnd3p1))
336 is_tiny = FALSE;
337 Dbl_decrement(opnd3p1,opnd3p2);
338 }
339 break;
340 case ROUNDMINUS:
341 if (Dbl_isone_sign(resultp1)) {
342 Dbl_increment(opnd3p1,opnd3p2);
343 if (Dbl_isone_hiddenoverflow(opnd3p1))
344 is_tiny = FALSE;
345 Dbl_decrement(opnd3p1,opnd3p2);
346 }
347 break;
348 case ROUNDNEAREST:
349 if (guardbit && (stickybit ||
350 Dbl_isone_lowmantissap2(opnd3p2))) {
351 Dbl_increment(opnd3p1,opnd3p2);
352 if (Dbl_isone_hiddenoverflow(opnd3p1))
353 is_tiny = FALSE;
354 Dbl_decrement(opnd3p1,opnd3p2);
355 }
356 break;
357 }
358 }
359
360 /*
361 * denormalize result or set to signed zero
362 */
363 stickybit = inexact;
364 Dbl_denormalize(opnd3p1,opnd3p2,dest_exponent,guardbit,
365 stickybit,inexact);
366
367 /* return rounded number */
368 if (inexact) {
369 switch (Rounding_mode()) {
370 case ROUNDPLUS:
371 if (Dbl_iszero_sign(resultp1)) {
372 Dbl_increment(opnd3p1,opnd3p2);
373 }
374 break;
375 case ROUNDMINUS:
376 if (Dbl_isone_sign(resultp1)) {
377 Dbl_increment(opnd3p1,opnd3p2);
378 }
379 break;
380 case ROUNDNEAREST:
381 if (guardbit && (stickybit ||
382 Dbl_isone_lowmantissap2(opnd3p2))) {
383 Dbl_increment(opnd3p1,opnd3p2);
384 }
385 break;
386 }
387 if (is_tiny) Set_underflowflag();
388 }
389 Dbl_set_exponentmantissa(resultp1,resultp2,opnd3p1,opnd3p2);
390 }
391 else Dbl_set_exponent(resultp1,dest_exponent);
392 Dbl_copytoptr(resultp1,resultp2,dstptr);
393
394 /* check for inexact */
395 if (inexact) {
396 if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
397 else Set_inexactflag();
398 }
399 return(NOEXCEPTION);
400}