1 /* $OpenBSD: fenv.c,v 1.4 2012/12/05 23:20:03 deraadt 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 28 #include <fenv.h> 29 30 /* 31 * The following constant represents the default floating-point environment 32 * (that is, the one installed at program startup) and has type pointer to 33 * const-qualified fenv_t. 34 * 35 * It can be used as an argument to the functions within the <fenv.h> header 36 * that manage the floating-point environment, namely fesetenv() and 37 * feupdateenv(). 38 */ 39 fenv_t __fe_dfl_env = 0; 40 41 /* 42 * The feclearexcept() function clears the supported floating-point exceptions 43 * represented by `excepts'. 44 */ 45 int 46 feclearexcept(int excepts) 47 { 48 fexcept_t r; 49 50 excepts &= FE_ALL_EXCEPT; 51 52 /* Save floating-point state register */ 53 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 54 55 r &= ~excepts; 56 57 /* Load floating-point state register */ 58 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 59 60 return 0; 61 } 62 63 /* 64 * The fegetexceptflag() function stores an implementation-defined 65 * representation of the states of the floating-point status flags indicated 66 * by the argument excepts in the object pointed to by the argument flagp. 67 */ 68 int 69 fegetexceptflag(fexcept_t *flagp, int excepts) 70 { 71 fexcept_t r; 72 73 excepts &= FE_ALL_EXCEPT; 74 75 /* Save floating-point state register */ 76 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 77 78 *flagp = r & excepts; 79 80 return 0; 81 } 82 83 84 /* 85 * This function sets the floating-point status flags indicated by the argument 86 * `excepts' to the states stored in the object pointed to by `flagp'. It does 87 * NOT raise any floating-point exceptions, but only sets the state of the flags. 88 */ 89 int 90 fesetexceptflag(const fexcept_t *flagp, int excepts) 91 { 92 fexcept_t r; 93 94 excepts &= FE_ALL_EXCEPT; 95 96 /* Save floating-point state register */ 97 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 98 99 r &= ~excepts; 100 r |= *flagp & excepts; 101 102 /* Load floating-point state register */ 103 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 104 105 return 0; 106 } 107 108 /* 109 * The feraiseexcept() function raises the supported floating-point exceptions 110 * represented by the argument `excepts'. 111 * 112 * The order in which these floating-point exceptions are raised is unspecified 113 * (by the standard). 114 */ 115 int 116 feraiseexcept(int excepts) 117 { 118 volatile double d; 119 120 excepts &= FE_ALL_EXCEPT; 121 122 /* 123 * With a compiler that supports the FENV_ACCESS pragma properly, simple 124 * expressions like '0.0 / 0.0' should be sufficient to generate traps. 125 * Unfortunately, we need to bring a volatile variable into the equation 126 * to prevent incorrect optimizations. 127 */ 128 if (excepts & FE_INVALID) { 129 d = 0.0; 130 d = 0.0 / d; 131 } 132 if (excepts & FE_DIVBYZERO) { 133 d = 0.0; 134 d = 1.0 / d; 135 } 136 if (excepts & FE_OVERFLOW) { 137 d = 0x1.ffp1023; 138 d *= 2.0; 139 } 140 if (excepts & FE_UNDERFLOW) { 141 d = 0x1p-1022; 142 d /= 0x1p1023; 143 } 144 if (excepts & FE_INEXACT) { 145 d = 0x1p-1022; 146 d += 1.0; 147 } 148 149 return 0; 150 } 151 152 /* 153 * The fetestexcept() function determines which of a specified subset of the 154 * floating-point exception flags are currently set. The `excepts' argument 155 * specifies the floating-point status flags to be queried. 156 */ 157 int 158 fetestexcept(int excepts) 159 { 160 fexcept_t r; 161 162 excepts &= FE_ALL_EXCEPT; 163 164 /* Save floating-point state register */ 165 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 166 167 return r & excepts; 168 } 169 170 /* 171 * The fegetround() function gets the current rounding direction. 172 */ 173 int 174 fegetround(void) 175 { 176 fenv_t r; 177 178 /* Save floating-point state register */ 179 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 180 181 return (r >> _ROUND_SHIFT) & _ROUND_MASK; 182 } 183 184 /* 185 * The fesetround() function establishes the rounding direction represented by 186 * its argument `round'. If the argument is not equal to the value of a rounding 187 * direction macro, the rounding direction is not changed. 188 */ 189 int 190 fesetround(int round) 191 { 192 fenv_t r; 193 194 if (round & ~_ROUND_MASK) 195 return -1; 196 197 /* Save floating-point state register */ 198 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 199 200 r &= ~(_ROUND_MASK << _ROUND_SHIFT); 201 r |= round << _ROUND_SHIFT; 202 203 /* Load floating-point state register */ 204 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 205 206 return 0; 207 } 208 209 /* 210 * The fegetenv() function attempts to store the current floating-point 211 * environment in the object pointed to by envp. 212 */ 213 int 214 fegetenv(fenv_t *envp) 215 { 216 /* Save floating-point state register */ 217 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (*envp)); 218 219 return 0; 220 } 221 222 223 /* 224 * The feholdexcept() function saves the current floating-point environment 225 * in the object pointed to by envp, clears the floating-point status flags, and 226 * then installs a non-stop (continue on floating-point exceptions) mode, if 227 * available, for all floating-point exceptions. 228 */ 229 int 230 feholdexcept(fenv_t *envp) 231 { 232 fenv_t r; 233 234 /* Save floating-point state register */ 235 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 236 237 *envp = r; 238 r &= ~(FE_ALL_EXCEPT | (FE_ALL_EXCEPT << _MASK_SHIFT)); 239 240 /* Load floating-point state register */ 241 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (r)); 242 243 return 0; 244 } 245 246 /* 247 * The fesetenv() function attempts to establish the floating-point environment 248 * represented by the object pointed to by envp. The argument `envp' points 249 * to an object set by a call to fegetenv() or feholdexcept(), or equal a 250 * floating-point environment macro. The fesetenv() function does not raise 251 * floating-point exceptions, but only installs the state of the floating-point 252 * status flags represented through its argument. 253 */ 254 int 255 fesetenv(const fenv_t *envp) 256 { 257 /* Load floating-point state register */ 258 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (*envp)); 259 260 return 0; 261 } 262 263 264 /* 265 * The feupdateenv() function saves the currently raised floating-point 266 * exceptions in its automatic storage, installs the floating-point environment 267 * represented by the object pointed to by `envp', and then raises the saved 268 * floating-point exceptions. The argument `envp' shall point to an object set 269 * by a call to feholdexcept() or fegetenv(), or equal a floating-point 270 * environment macro. 271 */ 272 int 273 feupdateenv(const fenv_t *envp) 274 { 275 fexcept_t r; 276 277 /* Save floating-point state register */ 278 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 279 280 /* Load floating-point state register */ 281 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (*envp)); 282 283 feraiseexcept(r & FE_ALL_EXCEPT); 284 285 return 0; 286 } 287 288 /* 289 * The following functions are extentions to the standard 290 */ 291 int 292 feenableexcept(int mask) 293 { 294 fenv_t old_r, new_r; 295 296 mask &= FE_ALL_EXCEPT; 297 298 /* Save floating-point state register */ 299 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (old_r)); 300 301 new_r = old_r | (mask << _MASK_SHIFT); 302 303 /* Load floating-point state register */ 304 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (new_r)); 305 306 return (old_r >> _MASK_SHIFT) & FE_ALL_EXCEPT; 307 } 308 309 int 310 fedisableexcept(int mask) 311 { 312 fenv_t old_r, new_r; 313 314 mask &= FE_ALL_EXCEPT; 315 316 /* Save floating-point state register */ 317 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (old_r)); 318 319 new_r = old_r & ~(mask << _MASK_SHIFT); 320 321 /* Load floating-point state register */ 322 __asm__ __volatile__ ("ldx %0, %%fsr" : : "m" (new_r)); 323 324 return (old_r >> _MASK_SHIFT) & FE_ALL_EXCEPT; 325 } 326 327 int 328 fegetexcept(void) 329 { 330 fenv_t r; 331 332 /* Save floating-point state register */ 333 __asm__ __volatile__ ("stx %%fsr, %0" : "=m" (r)); 334 335 return (r & (FE_ALL_EXCEPT << _MASK_SHIFT)) >> _MASK_SHIFT; 336 } 337