1 /* $NetBSD: fenv.c,v 1.2 2015/01/13 11:16:06 martin Exp $ */
2
3 /*-
4 * Copyright (c) 2004-2005 David Schultz <das@FreeBSD.ORG>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 */
26 #include <sys/cdefs.h>
27 __RCSID("$NetBSD: fenv.c,v 1.2 2015/01/13 11:16:06 martin Exp $");
28
29 #include <assert.h>
30 #include <fenv.h>
31
32 /*
33 * Convert from exception flags (__BITS(27,32)) to exception enable bits
34 * (__BITS(5,0)) by right-shifting this much:
35 */
36 #define FE_FLAGS_SHIFT 27
37
38 /*
39 * Mask all rounding mode bits
40 */
41 #define FE_ROUND_MASK (FE_TONEAREST | FE_DOWNWARD | \
42 FE_UPWARD | FE_TOWARDZERO)
43
44 /* Load lower 32 bits from floating-point state register */
45 static inline uint32_t
readfpsr(void)46 readfpsr(void)
47 {
48 uint32_t rv;
49
50 __asm__ __volatile__ ("fstws %%fr0, %0" : "=m"(rv));
51 return rv;
52 }
53
54 /* Save floating-point state register */
55 static inline void
writefpsr(uint32_t val)56 writefpsr(uint32_t val)
57 {
58 __asm__ __volatile__("fldws %0,%%fr0" : : "m"(val));
59 }
60
61 /*
62 * The feclearexcept() function clears the supported floating-point exceptions
63 * represented by `excepts'.
64 */
65 int
feclearexcept(int excepts)66 feclearexcept(int excepts)
67 {
68 fexcept_t r;
69 int ex;
70
71 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
72
73 ex = (excepts & FE_ALL_EXCEPT) << FE_FLAGS_SHIFT;
74
75 r = readfpsr();
76 r &= ~ex;
77 writefpsr(r);
78
79 /* Success */
80 return 0;
81 }
82
83 /*
84 * The fegetexceptflag() function stores an implementation-defined
85 * representation of the states of the floating-point status flags indicated
86 * by the argument excepts in the object pointed to by the argument flagp.
87 */
88 int
fegetexceptflag(fexcept_t * flagp,int excepts)89 fegetexceptflag(fexcept_t *flagp, int excepts)
90 {
91 fexcept_t r;
92 int ex;
93
94 _DIAGASSERT(flagp != NULL);
95 _DIAGASSERT((excepts & ~_FE_ALL_EXCEPT) == 0);
96
97 ex = (excepts & FE_ALL_EXCEPT) << FE_FLAGS_SHIFT;
98
99 r = readfpsr();
100 *flagp = (r & ex) >> FE_FLAGS_SHIFT;
101
102 /* Success */
103 return 0;
104 }
105
106
107 /*
108 * This function sets the floating-point status flags indicated by the argument
109 * `excepts' to the states stored in the object pointed to by `flagp'. It does
110 * NOT raise any floating-point exceptions, but only sets the state of the flags.
111 */
112 int
fesetexceptflag(const fexcept_t * flagp,int excepts)113 fesetexceptflag(const fexcept_t *flagp, int excepts)
114 {
115 fexcept_t r;
116 int ex;
117
118 _DIAGASSERT(flagp != NULL);
119 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
120
121 ex = (excepts & FE_ALL_EXCEPT) << FE_FLAGS_SHIFT;
122
123 r = readfpsr();
124 r &= ~ex;
125 r |= (*flagp << FE_FLAGS_SHIFT) & ex;
126 writefpsr(r);
127
128 /* Success */
129 return 0;
130 }
131
132 /*
133 * The feraiseexcept() function raises the supported floating-point exceptions
134 * represented by the argument `excepts'.
135 *
136 * The order in which these floating-point exceptions are raised is unspecified
137 * (by the standard).
138 */
139 int
feraiseexcept(int excepts)140 feraiseexcept(int excepts)
141 {
142 volatile double d;
143 int ex;
144
145 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
146
147 ex = excepts & FE_ALL_EXCEPT;
148
149 /*
150 * With a compiler that supports the FENV_ACCESS pragma properly, simple
151 * expressions like '0.0 / 0.0' should be sufficient to generate traps.
152 * Unfortunately, we need to bring a volatile variable into the equation
153 * to prevent incorrect optimizations.
154 */
155 if (ex & FE_INVALID) {
156 d = 0.0;
157 d = 0.0 / d;
158 }
159 if (ex & FE_DIVBYZERO) {
160 d = 0.0;
161 d = 1.0 / d;
162 }
163 if (ex & FE_OVERFLOW) {
164 d = 0x1.ffp1023;
165 d *= 2.0;
166 }
167 if (ex & FE_UNDERFLOW) {
168 d = 0x1p-1022;
169 d /= 0x1p1023;
170 }
171 if (ex & FE_INEXACT) {
172 d = 0x1p-1022;
173 d += 1.0;
174 }
175
176 /* Success */
177 return 0;
178 }
179
180 /*
181 * The fetestexcept() function determines which of a specified subset of the
182 * floating-point exception flags are currently set. The `excepts' argument
183 * specifies the floating-point status flags to be queried.
184 */
185 int
fetestexcept(int excepts)186 fetestexcept(int excepts)
187 {
188 fexcept_t r;
189
190 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
191
192 r = readfpsr();
193
194 return (r >> FE_FLAGS_SHIFT) & (excepts & FE_ALL_EXCEPT);
195 }
196
197 /*
198 * The fegetround() function gets the current rounding direction.
199 */
200 int
fegetround(void)201 fegetround(void)
202 {
203 fenv_t r;
204
205 r = readfpsr();
206
207 return r & FE_ROUND_MASK;
208 }
209
210 /*
211 * The fesetround() function establishes the rounding direction represented by
212 * its argument `round'. If the argument is not equal to the value of a rounding
213 * direction macro, the rounding direction is not changed.
214 */
215 int
fesetround(int round)216 fesetround(int round)
217 {
218 fenv_t r;
219
220 _DIAGASSERT((round & ~FE_ROUND_MASK) == 0);
221 if (round & ~FE_ROUND_MASK)
222 return -1;
223
224 r = readfpsr();
225 r &= ~FE_ROUND_MASK;
226 r |= round;
227 writefpsr(r);
228
229 /* Success */
230 return 0;
231 }
232
233 /*
234 * The fegetenv() function attempts to store the current floating-point
235 * environment in the object pointed to by envp.
236 */
237 int
fegetenv(fenv_t * envp)238 fegetenv(fenv_t *envp)
239 {
240 _DIAGASSERT(envp != NULL);
241
242 *envp = readfpsr();
243
244 /* Success */
245 return 0;
246 }
247
248
249 /*
250 * The feholdexcept() function saves the current floating-point environment
251 * in the object pointed to by envp, clears the floating-point status flags, and
252 * then installs a non-stop (continue on floating-point exceptions) mode, if
253 * available, for all floating-point exceptions.
254 */
255 int
feholdexcept(fenv_t * envp)256 feholdexcept(fenv_t *envp)
257 {
258 fenv_t r;
259
260 _DIAGASSERT(envp != NULL);
261
262 r = readfpsr();
263 *envp = r;
264 r &= ~FE_ALL_EXCEPT;
265 writefpsr(r);
266
267 /* Success */
268 return 0;
269 }
270
271 /*
272 * The fesetenv() function attempts to establish the floating-point environment
273 * represented by the object pointed to by envp. The argument `envp' points
274 * to an object set by a call to fegetenv() or feholdexcept(), or equal a
275 * floating-point environment macro. The fesetenv() function does not raise
276 * floating-point exceptions, but only installs the state of the floating-point
277 * status flags represented through its argument.
278 */
279 int
fesetenv(const fenv_t * envp)280 fesetenv(const fenv_t *envp)
281 {
282 _DIAGASSERT(envp != NULL);
283
284 writefpsr(*envp);
285
286 /* Success */
287 return 0;
288 }
289
290
291 /*
292 * The feupdateenv() function saves the currently raised floating-point
293 * exceptions in its automatic storage, installs the floating-point environment
294 * represented by the object pointed to by `envp', and then raises the saved
295 * floating-point exceptions. The argument `envp' shall point to an object set
296 * by a call to feholdexcept() or fegetenv(), or equal a floating-point
297 * environment macro.
298 */
299 int
feupdateenv(const fenv_t * envp)300 feupdateenv(const fenv_t *envp)
301 {
302 fexcept_t r;
303
304 _DIAGASSERT(envp != NULL);
305
306 r = readfpsr();
307 writefpsr(*envp);
308
309 _DIAGASSERT((r & ~FE_ALL_EXCEPT) == 0);
310 feraiseexcept(r & FE_ALL_EXCEPT);
311
312 /* Success */
313 return 0;
314 }
315
316 /*
317 * The following functions are extentions to the standard
318 */
319 int
feenableexcept(int mask)320 feenableexcept(int mask)
321 {
322 fenv_t old_r, new_r;
323
324 old_r = readfpsr();
325 new_r = old_r | (mask & FE_ALL_EXCEPT);
326 writefpsr(new_r);
327
328 return old_r & FE_ALL_EXCEPT;
329 }
330
331 int
fedisableexcept(int mask)332 fedisableexcept(int mask)
333 {
334 fenv_t old_r, new_r;
335
336 old_r = readfpsr();
337 new_r = old_r & ~(mask & FE_ALL_EXCEPT);
338 writefpsr(new_r);
339
340 return old_r & FE_ALL_EXCEPT;
341 }
342
343 int
fegetexcept(void)344 fegetexcept(void)
345 {
346 fenv_t r;
347
348 r = readfpsr();
349 return r & FE_ALL_EXCEPT;
350 }
351