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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/sfmpy.c $Revision: 1.1 $ | |
26 | * | |
27 | * Purpose: | |
28 | * Single Precision Floating-point Multiply | |
29 | * | |
30 | * External Interfaces: | |
31 | * sgl_fmpy(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 Multiply | |
47 | */ | |
48 | ||
49 | int | |
50 | sgl_fmpy( | |
51 | sgl_floating_point *srcptr1, | |
52 | sgl_floating_point *srcptr2, | |
53 | sgl_floating_point *dstptr, | |
54 | unsigned int *status) | |
55 | { | |
56 | register unsigned int opnd1, opnd2, opnd3, result; | |
57 | register int dest_exponent, count; | |
58 | register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE; | |
59 | boolean is_tiny; | |
60 | ||
61 | opnd1 = *srcptr1; | |
62 | opnd2 = *srcptr2; | |
63 | /* | |
64 | * set sign bit of result | |
65 | */ | |
66 | if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result); | |
67 | else Sgl_setzero(result); | |
68 | /* | |
69 | * check first operand for NaN's or infinity | |
70 | */ | |
71 | if (Sgl_isinfinity_exponent(opnd1)) { | |
72 | if (Sgl_iszero_mantissa(opnd1)) { | |
73 | if (Sgl_isnotnan(opnd2)) { | |
74 | if (Sgl_iszero_exponentmantissa(opnd2)) { | |
75 | /* | |
76 | * invalid since operands are infinity | |
77 | * and zero | |
78 | */ | |
79 | if (Is_invalidtrap_enabled()) | |
80 | return(INVALIDEXCEPTION); | |
81 | Set_invalidflag(); | |
82 | Sgl_makequietnan(result); | |
83 | *dstptr = result; | |
84 | return(NOEXCEPTION); | |
85 | } | |
86 | /* | |
87 | * return infinity | |
88 | */ | |
89 | Sgl_setinfinity_exponentmantissa(result); | |
90 | *dstptr = result; | |
91 | return(NOEXCEPTION); | |
92 | } | |
93 | } | |
94 | else { | |
95 | /* | |
96 | * is NaN; signaling or quiet? | |
97 | */ | |
98 | if (Sgl_isone_signaling(opnd1)) { | |
99 | /* trap if INVALIDTRAP enabled */ | |
100 | if (Is_invalidtrap_enabled()) | |
101 | return(INVALIDEXCEPTION); | |
102 | /* make NaN quiet */ | |
103 | Set_invalidflag(); | |
104 | Sgl_set_quiet(opnd1); | |
105 | } | |
106 | /* | |
107 | * is second operand a signaling NaN? | |
108 | */ | |
109 | else if (Sgl_is_signalingnan(opnd2)) { | |
110 | /* trap if INVALIDTRAP enabled */ | |
111 | if (Is_invalidtrap_enabled()) | |
112 | return(INVALIDEXCEPTION); | |
113 | /* make NaN quiet */ | |
114 | Set_invalidflag(); | |
115 | Sgl_set_quiet(opnd2); | |
116 | *dstptr = opnd2; | |
117 | return(NOEXCEPTION); | |
118 | } | |
119 | /* | |
120 | * return quiet NaN | |
121 | */ | |
122 | *dstptr = opnd1; | |
123 | return(NOEXCEPTION); | |
124 | } | |
125 | } | |
126 | /* | |
127 | * check second operand for NaN's or infinity | |
128 | */ | |
129 | if (Sgl_isinfinity_exponent(opnd2)) { | |
130 | if (Sgl_iszero_mantissa(opnd2)) { | |
131 | if (Sgl_iszero_exponentmantissa(opnd1)) { | |
132 | /* invalid since operands are zero & infinity */ | |
133 | if (Is_invalidtrap_enabled()) | |
134 | return(INVALIDEXCEPTION); | |
135 | Set_invalidflag(); | |
136 | Sgl_makequietnan(opnd2); | |
137 | *dstptr = opnd2; | |
138 | return(NOEXCEPTION); | |
139 | } | |
140 | /* | |
141 | * return infinity | |
142 | */ | |
143 | Sgl_setinfinity_exponentmantissa(result); | |
144 | *dstptr = result; | |
145 | return(NOEXCEPTION); | |
146 | } | |
147 | /* | |
148 | * is NaN; signaling or quiet? | |
149 | */ | |
150 | if (Sgl_isone_signaling(opnd2)) { | |
151 | /* trap if INVALIDTRAP enabled */ | |
152 | if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION); | |
153 | ||
154 | /* make NaN quiet */ | |
155 | Set_invalidflag(); | |
156 | Sgl_set_quiet(opnd2); | |
157 | } | |
158 | /* | |
159 | * return quiet NaN | |
160 | */ | |
161 | *dstptr = opnd2; | |
162 | return(NOEXCEPTION); | |
163 | } | |
164 | /* | |
165 | * Generate exponent | |
166 | */ | |
167 | dest_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS; | |
168 | ||
169 | /* | |
170 | * Generate mantissa | |
171 | */ | |
172 | if (Sgl_isnotzero_exponent(opnd1)) { | |
173 | /* set hidden bit */ | |
174 | Sgl_clear_signexponent_set_hidden(opnd1); | |
175 | } | |
176 | else { | |
177 | /* check for zero */ | |
178 | if (Sgl_iszero_mantissa(opnd1)) { | |
179 | Sgl_setzero_exponentmantissa(result); | |
180 | *dstptr = result; | |
181 | return(NOEXCEPTION); | |
182 | } | |
183 | /* is denormalized, adjust exponent */ | |
184 | Sgl_clear_signexponent(opnd1); | |
185 | Sgl_leftshiftby1(opnd1); | |
186 | Sgl_normalize(opnd1,dest_exponent); | |
187 | } | |
188 | /* opnd2 needs to have hidden bit set with msb in hidden bit */ | |
189 | if (Sgl_isnotzero_exponent(opnd2)) { | |
190 | Sgl_clear_signexponent_set_hidden(opnd2); | |
191 | } | |
192 | else { | |
193 | /* check for zero */ | |
194 | if (Sgl_iszero_mantissa(opnd2)) { | |
195 | Sgl_setzero_exponentmantissa(result); | |
196 | *dstptr = result; | |
197 | return(NOEXCEPTION); | |
198 | } | |
199 | /* is denormalized; want to normalize */ | |
200 | Sgl_clear_signexponent(opnd2); | |
201 | Sgl_leftshiftby1(opnd2); | |
202 | Sgl_normalize(opnd2,dest_exponent); | |
203 | } | |
204 | ||
205 | /* Multiply two source mantissas together */ | |
206 | ||
207 | Sgl_leftshiftby4(opnd2); /* make room for guard bits */ | |
208 | Sgl_setzero(opnd3); | |
209 | /* | |
210 | * Four bits at a time are inspected in each loop, and a | |
211 | * simple shift and add multiply algorithm is used. | |
212 | */ | |
213 | for (count=1;count<SGL_P;count+=4) { | |
214 | stickybit |= Slow4(opnd3); | |
215 | Sgl_rightshiftby4(opnd3); | |
216 | if (Sbit28(opnd1)) Sall(opnd3) += (Sall(opnd2) << 3); | |
217 | if (Sbit29(opnd1)) Sall(opnd3) += (Sall(opnd2) << 2); | |
218 | if (Sbit30(opnd1)) Sall(opnd3) += (Sall(opnd2) << 1); | |
219 | if (Sbit31(opnd1)) Sall(opnd3) += Sall(opnd2); | |
220 | Sgl_rightshiftby4(opnd1); | |
221 | } | |
222 | /* make sure result is left-justified */ | |
223 | if (Sgl_iszero_sign(opnd3)) { | |
224 | Sgl_leftshiftby1(opnd3); | |
225 | } | |
226 | else { | |
227 | /* result mantissa >= 2. */ | |
228 | dest_exponent++; | |
229 | } | |
230 | /* check for denormalized result */ | |
231 | while (Sgl_iszero_sign(opnd3)) { | |
232 | Sgl_leftshiftby1(opnd3); | |
233 | dest_exponent--; | |
234 | } | |
235 | /* | |
236 | * check for guard, sticky and inexact bits | |
237 | */ | |
238 | stickybit |= Sgl_all(opnd3) << (SGL_BITLENGTH - SGL_EXP_LENGTH + 1); | |
239 | guardbit = Sbit24(opnd3); | |
240 | inexact = guardbit | stickybit; | |
241 | ||
242 | /* re-align mantissa */ | |
243 | Sgl_rightshiftby8(opnd3); | |
244 | ||
245 | /* | |
246 | * round result | |
247 | */ | |
248 | if (inexact && (dest_exponent>0 || Is_underflowtrap_enabled())) { | |
249 | Sgl_clear_signexponent(opnd3); | |
250 | switch (Rounding_mode()) { | |
251 | case ROUNDPLUS: | |
252 | if (Sgl_iszero_sign(result)) | |
253 | Sgl_increment(opnd3); | |
254 | break; | |
255 | case ROUNDMINUS: | |
256 | if (Sgl_isone_sign(result)) | |
257 | Sgl_increment(opnd3); | |
258 | break; | |
259 | case ROUNDNEAREST: | |
260 | if (guardbit) { | |
261 | if (stickybit || Sgl_isone_lowmantissa(opnd3)) | |
262 | Sgl_increment(opnd3); | |
263 | } | |
264 | } | |
265 | if (Sgl_isone_hidden(opnd3)) dest_exponent++; | |
266 | } | |
267 | Sgl_set_mantissa(result,opnd3); | |
268 | ||
269 | /* | |
270 | * Test for overflow | |
271 | */ | |
272 | if (dest_exponent >= SGL_INFINITY_EXPONENT) { | |
273 | /* trap if OVERFLOWTRAP enabled */ | |
274 | if (Is_overflowtrap_enabled()) { | |
275 | /* | |
276 | * Adjust bias of result | |
277 | */ | |
278 | Sgl_setwrapped_exponent(result,dest_exponent,ovfl); | |
279 | *dstptr = result; | |
280 | if (inexact) | |
281 | if (Is_inexacttrap_enabled()) | |
282 | return(OVERFLOWEXCEPTION | INEXACTEXCEPTION); | |
283 | else Set_inexactflag(); | |
284 | return(OVERFLOWEXCEPTION); | |
285 | } | |
286 | inexact = TRUE; | |
287 | Set_overflowflag(); | |
288 | /* set result to infinity or largest number */ | |
289 | Sgl_setoverflow(result); | |
290 | } | |
291 | /* | |
292 | * Test for underflow | |
293 | */ | |
294 | else if (dest_exponent <= 0) { | |
295 | /* trap if UNDERFLOWTRAP enabled */ | |
296 | if (Is_underflowtrap_enabled()) { | |
297 | /* | |
298 | * Adjust bias of result | |
299 | */ | |
300 | Sgl_setwrapped_exponent(result,dest_exponent,unfl); | |
301 | *dstptr = result; | |
302 | if (inexact) | |
303 | if (Is_inexacttrap_enabled()) | |
304 | return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION); | |
305 | else Set_inexactflag(); | |
306 | return(UNDERFLOWEXCEPTION); | |
307 | } | |
308 | ||
309 | /* Determine if should set underflow flag */ | |
310 | is_tiny = TRUE; | |
311 | if (dest_exponent == 0 && inexact) { | |
312 | switch (Rounding_mode()) { | |
313 | case ROUNDPLUS: | |
314 | if (Sgl_iszero_sign(result)) { | |
315 | Sgl_increment(opnd3); | |
316 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
317 | is_tiny = FALSE; | |
318 | Sgl_decrement(opnd3); | |
319 | } | |
320 | break; | |
321 | case ROUNDMINUS: | |
322 | if (Sgl_isone_sign(result)) { | |
323 | Sgl_increment(opnd3); | |
324 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
325 | is_tiny = FALSE; | |
326 | Sgl_decrement(opnd3); | |
327 | } | |
328 | break; | |
329 | case ROUNDNEAREST: | |
330 | if (guardbit && (stickybit || | |
331 | Sgl_isone_lowmantissa(opnd3))) { | |
332 | Sgl_increment(opnd3); | |
333 | if (Sgl_isone_hiddenoverflow(opnd3)) | |
334 | is_tiny = FALSE; | |
335 | Sgl_decrement(opnd3); | |
336 | } | |
337 | break; | |
338 | } | |
339 | } | |
340 | ||
341 | /* | |
342 | * denormalize result or set to signed zero | |
343 | */ | |
344 | stickybit = inexact; | |
345 | Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact); | |
346 | ||
347 | /* return zero or smallest number */ | |
348 | if (inexact) { | |
349 | switch (Rounding_mode()) { | |
350 | case ROUNDPLUS: | |
351 | if (Sgl_iszero_sign(result)) { | |
352 | Sgl_increment(opnd3); | |
353 | } | |
354 | break; | |
355 | case ROUNDMINUS: | |
356 | if (Sgl_isone_sign(result)) { | |
357 | Sgl_increment(opnd3); | |
358 | } | |
359 | break; | |
360 | case ROUNDNEAREST: | |
361 | if (guardbit && (stickybit || | |
362 | Sgl_isone_lowmantissa(opnd3))) { | |
363 | Sgl_increment(opnd3); | |
364 | } | |
365 | break; | |
366 | } | |
367 | if (is_tiny) Set_underflowflag(); | |
368 | } | |
369 | Sgl_set_exponentmantissa(result,opnd3); | |
370 | } | |
371 | else Sgl_set_exponent(result,dest_exponent); | |
372 | *dstptr = result; | |
373 | ||
374 | /* check for inexact */ | |
375 | if (inexact) { | |
376 | if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION); | |
377 | else Set_inexactflag(); | |
378 | } | |
379 | return(NOEXCEPTION); | |
380 | } |