1 /* $OpenBSD: fenv.c,v 1.3 2011/04/28 17:34:23 martynas Exp $ */ 2 /* $NetBSD: fenv.c,v 1.1 2011/01/31 00:19:33 christos Exp $ */ 3 4 /*- 5 * Copyright (c) 2004-2005 David Schultz <das@FreeBSD.ORG> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 */ 27 #include <sys/cdefs.h> 28 29 #include <fenv.h> 30 31 /* 32 * The following constant represents the default floating-point environment 33 * (that is, the one installed at program startup) and has type pointer to 34 * const-qualified fenv_t. 35 * 36 * It can be used as an argument to the functions within the <fenv.h> header 37 * that manage the floating-point environment, namely fesetenv() and 38 * feupdateenv(). 39 */ 40 fenv_t __fe_dfl_env = 0; 41 42 /* 43 * The feclearexcept() function clears the supported floating-point exceptions 44 * represented by `excepts'. 45 */ 46 int 47 feclearexcept(int excepts) 48 { 49 fexcept_t r; 50 51 excepts &= FE_ALL_EXCEPT; 52 53 /* Save floating-point state register */ 54 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 55 56 r &= ~excepts; 57 58 /* Load floating-point state register */ 59 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 60 61 return 0; 62 } 63 64 /* 65 * The fegetexceptflag() function stores an implementation-defined 66 * representation of the states of the floating-point status flags indicated 67 * by the argument excepts in the object pointed to by the argument flagp. 68 */ 69 int 70 fegetexceptflag(fexcept_t *flagp, int excepts) 71 { 72 fexcept_t r; 73 74 excepts &= FE_ALL_EXCEPT; 75 76 /* Save floating-point state register */ 77 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 78 79 *flagp = r & excepts; 80 81 return 0; 82 } 83 84 85 /* 86 * This function sets the floating-point status flags indicated by the argument 87 * `excepts' to the states stored in the object pointed to by `flagp'. It does 88 * NOT raise any floating-point exceptions, but only sets the state of the flags. 89 */ 90 int 91 fesetexceptflag(const fexcept_t *flagp, int excepts) 92 { 93 fexcept_t r; 94 95 excepts &= FE_ALL_EXCEPT; 96 97 /* Save floating-point state register */ 98 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 99 100 r &= ~excepts; 101 r |= *flagp & excepts; 102 103 /* Load floating-point state register */ 104 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 105 106 return 0; 107 } 108 109 /* 110 * The feraiseexcept() function raises the supported floating-point exceptions 111 * represented by the argument `excepts'. 112 * 113 * The order in which these floating-point exceptions are raised is unspecified 114 * (by the standard). 115 */ 116 int 117 feraiseexcept(int excepts) 118 { 119 volatile double d; 120 121 excepts &= FE_ALL_EXCEPT; 122 123 /* 124 * With a compiler that supports the FENV_ACCESS pragma properly, simple 125 * expressions like '0.0 / 0.0' should be sufficient to generate traps. 126 * Unfortunately, we need to bring a volatile variable into the equation 127 * to prevent incorrect optimizations. 128 */ 129 if (excepts & FE_INVALID) { 130 d = 0.0; 131 d = 0.0 / d; 132 } 133 if (excepts & FE_DIVBYZERO) { 134 d = 0.0; 135 d = 1.0 / d; 136 } 137 if (excepts & FE_OVERFLOW) { 138 d = 0x1.ffp1023; 139 d *= 2.0; 140 } 141 if (excepts & FE_UNDERFLOW) { 142 d = 0x1p-1022; 143 d /= 0x1p1023; 144 } 145 if (excepts & FE_INEXACT) { 146 d = 0x1p-1022; 147 d += 1.0; 148 } 149 150 return 0; 151 } 152 153 /* 154 * The fetestexcept() function determines which of a specified subset of the 155 * floating-point exception flags are currently set. The `excepts' argument 156 * specifies the floating-point status flags to be queried. 157 */ 158 int 159 fetestexcept(int excepts) 160 { 161 fexcept_t r; 162 163 excepts &= FE_ALL_EXCEPT; 164 165 /* Save floating-point state register */ 166 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 167 168 return r & excepts; 169 } 170 171 /* 172 * The fegetround() function gets the current rounding direction. 173 */ 174 int 175 fegetround(void) 176 { 177 fenv_t r; 178 179 /* Save floating-point state register */ 180 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 181 182 return (r >> _ROUND_SHIFT) & _ROUND_MASK; 183 } 184 185 /* 186 * The fesetround() function establishes the rounding direction represented by 187 * its argument `round'. If the argument is not equal to the value of a rounding 188 * direction macro, the rounding direction is not changed. 189 */ 190 int 191 fesetround(int round) 192 { 193 fenv_t r; 194 195 if (round & ~_ROUND_MASK) 196 return -1; 197 198 /* Save floating-point state register */ 199 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 200 201 r &= ~(_ROUND_MASK << _ROUND_SHIFT); 202 r |= round << _ROUND_SHIFT; 203 204 /* Load floating-point state register */ 205 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 206 207 return 0; 208 } 209 210 /* 211 * The fegetenv() function attempts to store the current floating-point 212 * environment in the object pointed to by envp. 213 */ 214 int 215 fegetenv(fenv_t *envp) 216 { 217 /* Save floating-point state register */ 218 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (*envp)); 219 220 return 0; 221 } 222 223 224 /* 225 * The feholdexcept() function saves the current floating-point environment 226 * in the object pointed to by envp, clears the floating-point status flags, and 227 * then installs a non-stop (continue on floating-point exceptions) mode, if 228 * available, for all floating-point exceptions. 229 */ 230 int 231 feholdexcept(fenv_t *envp) 232 { 233 fenv_t r; 234 235 /* Save floating-point state register */ 236 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 237 238 *envp = r; 239 r &= ~(FE_ALL_EXCEPT | (FE_ALL_EXCEPT << _MASK_SHIFT)); 240 241 /* Load floating-point state register */ 242 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 243 244 return 0; 245 } 246 247 /* 248 * The fesetenv() function attempts to establish the floating-point environment 249 * represented by the object pointed to by envp. The argument `envp' points 250 * to an object set by a call to fegetenv() or feholdexcept(), or equal a 251 * floating-point environment macro. The fesetenv() function does not raise 252 * floating-point exceptions, but only installs the state of the floating-point 253 * status flags represented through its argument. 254 */ 255 int 256 fesetenv(const fenv_t *envp) 257 { 258 /* Load floating-point state register */ 259 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (*envp)); 260 261 return 0; 262 } 263 264 265 /* 266 * The feupdateenv() function saves the currently raised floating-point 267 * exceptions in its automatic storage, installs the floating-point environment 268 * represented by the object pointed to by `envp', and then raises the saved 269 * floating-point exceptions. The argument `envp' shall point to an object set 270 * by a call to feholdexcept() or fegetenv(), or equal a floating-point 271 * environment macro. 272 */ 273 int 274 feupdateenv(const fenv_t *envp) 275 { 276 fexcept_t r; 277 278 /* Save floating-point state register */ 279 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 280 281 /* Load floating-point state register */ 282 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (*envp)); 283 284 feraiseexcept(r & FE_ALL_EXCEPT); 285 286 return 0; 287 } 288 289 /* 290 * The following functions are extentions to the standard 291 */ 292 int 293 feenableexcept(int mask) 294 { 295 fenv_t old_r, new_r; 296 297 mask &= FE_ALL_EXCEPT; 298 299 /* Save floating-point state register */ 300 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (old_r)); 301 302 new_r = old_r | (mask << _MASK_SHIFT); 303 304 /* Load floating-point state register */ 305 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (new_r)); 306 307 return (old_r >> _MASK_SHIFT) & FE_ALL_EXCEPT; 308 } 309 310 int 311 fedisableexcept(int mask) 312 { 313 fenv_t old_r, new_r; 314 315 mask &= FE_ALL_EXCEPT; 316 317 /* Save floating-point state register */ 318 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (old_r)); 319 320 new_r = old_r & ~(mask << _MASK_SHIFT); 321 322 /* Load floating-point state register */ 323 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (new_r)); 324 325 return (old_r >> _MASK_SHIFT) & FE_ALL_EXCEPT; 326 } 327 328 int 329 fegetexcept(void) 330 { 331 fenv_t r; 332 333 /* Save floating-point state register */ 334 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 335 336 return (r & (FE_ALL_EXCEPT << _MASK_SHIFT)) >> _MASK_SHIFT; 337 } 338