1 /* $OpenBSD: fenv.c,v 1.4 2014/04/18 15:09:52 guenther Exp $ */ 2 /* $NetBSD: fenv.c,v 1.1 2010/07/31 21:47:53 joerg Exp $ */ 3 4 /*- 5 * Copyright (c) 2004-2005 David Schultz <das (at) 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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #include <fenv.h> 31 #include <machine/npx.h> 32 33 /* 34 * The following constant represents the default floating-point environment 35 * (that is, the one installed at program startup) and has type pointer to 36 * const-qualified fenv_t. 37 * 38 * It can be used as an argument to the functions within the <fenv.h> header 39 * that manage the floating-point environment, namely fesetenv() and 40 * feupdateenv(). 41 * 42 * x87 fpu registers are 16bit wide. The upper bits, 31-16, are marked as 43 * RESERVED. 44 */ 45 fenv_t __fe_dfl_env = { 46 { 47 0xffff0000 | __INITIAL_FPUCW__, /* Control word register */ 48 0xffff0000, /* Status word register */ 49 0xffffffff, /* Tag word register */ 50 { 51 0x00000000, 52 0x00000000, 53 0x00000000, 54 0xffff0000 55 } 56 }, 57 __INITIAL_MXCSR__ /* MXCSR register */ 58 }; 59 60 61 /* 62 * The feclearexcept() function clears the supported floating-point exceptions 63 * represented by `excepts'. 64 */ 65 int 66 feclearexcept(int excepts) 67 { 68 fenv_t fenv; 69 unsigned int mxcsr; 70 71 excepts &= FE_ALL_EXCEPT; 72 73 /* Store the current x87 floating-point environment */ 74 __asm__ volatile ("fnstenv %0" : "=m" (fenv)); 75 76 /* Clear the requested floating-point exceptions */ 77 fenv.__x87.__status &= ~excepts; 78 79 /* Load the x87 floating-point environent */ 80 __asm__ volatile ("fldenv %0" : : "m" (fenv)); 81 82 /* Same for SSE environment */ 83 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 84 mxcsr &= ~excepts; 85 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 86 87 return (0); 88 } 89 90 /* 91 * The fegetexceptflag() function stores an implementation-defined 92 * representation of the states of the floating-point status flags indicated by 93 * the argument excepts in the object pointed to by the argument flagp. 94 */ 95 int 96 fegetexceptflag(fexcept_t *flagp, int excepts) 97 { 98 unsigned short status; 99 unsigned int mxcsr; 100 101 excepts &= FE_ALL_EXCEPT; 102 103 /* Store the current x87 status register */ 104 __asm__ volatile ("fnstsw %0" : "=am" (status)); 105 106 /* Store the MXCSR register */ 107 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 108 109 /* Store the results in flagp */ 110 *flagp = (status | mxcsr) & excepts; 111 112 return (0); 113 } 114 115 /* 116 * The feraiseexcept() function raises the supported floating-point exceptions 117 * represented by the argument `excepts'. 118 * 119 * The standard explicitly allows us to execute an instruction that has the 120 * exception as a side effect, but we choose to manipulate the status register 121 * directly. 122 * 123 * The validation of input is being deferred to fesetexceptflag(). 124 */ 125 int 126 feraiseexcept(int excepts) 127 { 128 excepts &= FE_ALL_EXCEPT; 129 130 fesetexceptflag((fexcept_t *)&excepts, excepts); 131 __asm__ volatile ("fwait"); 132 133 return (0); 134 } 135 136 /* 137 * This function sets the floating-point status flags indicated by the argument 138 * `excepts' to the states stored in the object pointed to by `flagp'. It does 139 * NOT raise any floating-point exceptions, but only sets the state of the flags. 140 */ 141 int 142 fesetexceptflag(const fexcept_t *flagp, int excepts) 143 { 144 fenv_t fenv; 145 unsigned int mxcsr; 146 147 excepts &= FE_ALL_EXCEPT; 148 149 /* Store the current x87 floating-point environment */ 150 __asm__ volatile ("fnstenv %0" : "=m" (fenv)); 151 152 /* Set the requested status flags */ 153 fenv.__x87.__status &= ~excepts; 154 fenv.__x87.__status |= *flagp & excepts; 155 156 /* Load the x87 floating-point environent */ 157 __asm__ volatile ("fldenv %0" : : "m" (fenv)); 158 159 /* Same for SSE environment */ 160 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 161 mxcsr &= ~excepts; 162 mxcsr |= *flagp & excepts; 163 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 164 165 return (0); 166 } 167 168 /* 169 * The fetestexcept() function determines which of a specified subset of the 170 * floating-point exception flags are currently set. The `excepts' argument 171 * specifies the floating-point status flags to be queried. 172 */ 173 int 174 fetestexcept(int excepts) 175 { 176 unsigned short status; 177 unsigned int mxcsr; 178 179 excepts &= FE_ALL_EXCEPT; 180 181 /* Store the current x87 status register */ 182 __asm__ volatile ("fnstsw %0" : "=am" (status)); 183 184 /* Store the MXCSR register state */ 185 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 186 187 return ((status | mxcsr) & excepts); 188 } 189 190 /* 191 * The fegetround() function gets the current rounding direction. 192 */ 193 int 194 fegetround(void) 195 { 196 unsigned short control; 197 198 /* 199 * We assume that the x87 and the SSE unit agree on the 200 * rounding mode. Reading the control word on the x87 turns 201 * out to be about 5 times faster than reading it on the SSE 202 * unit on an Opteron 244. 203 */ 204 __asm__ volatile ("fnstcw %0" : "=m" (control)); 205 206 return (control & _X87_ROUND_MASK); 207 } 208 209 /* 210 * The fesetround() function establishes the rounding direction represented by 211 * its argument `round'. If the argument is not equal to the value of a rounding 212 * direction macro, the rounding direction is not changed. 213 */ 214 int 215 fesetround(int round) 216 { 217 unsigned short control; 218 unsigned int mxcsr; 219 220 /* Check whether requested rounding direction is supported */ 221 if (round & ~_X87_ROUND_MASK) 222 return (-1); 223 224 /* Store the current x87 control word register */ 225 __asm__ volatile ("fnstcw %0" : "=m" (control)); 226 227 /* Set the rounding direction */ 228 control &= ~_X87_ROUND_MASK; 229 control |= round; 230 231 /* Load the x87 control word register */ 232 __asm__ volatile ("fldcw %0" : : "m" (control)); 233 234 /* Same for the SSE environment */ 235 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 236 mxcsr &= ~(_X87_ROUND_MASK << _SSE_ROUND_SHIFT); 237 mxcsr |= round << _SSE_ROUND_SHIFT; 238 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 239 240 return (0); 241 } 242 243 /* 244 * The fegetenv() function attempts to store the current floating-point 245 * environment in the object pointed to by envp. 246 */ 247 int 248 fegetenv(fenv_t *envp) 249 { 250 /* Store the current x87 floating-point environment */ 251 __asm__ volatile ("fnstenv %0" : "=m" (*envp)); 252 253 /* Store the MXCSR register state */ 254 __asm__ volatile ("stmxcsr %0" : "=m" (envp->__mxcsr)); 255 256 /* 257 * When an FNSTENV instruction is executed, all pending exceptions are 258 * essentially lost (either the x87 FPU status register is cleared or 259 * all exceptions are masked). 260 * 261 * 8.6 X87 FPU EXCEPTION SYNCHRONIZATION - 262 * Intel(R) 64 and IA-32 Architectures Softare Developer's Manual - Vol1 263 */ 264 __asm__ volatile ("fldcw %0" : : "m" (envp->__x87.__control)); 265 266 return (0); 267 } 268 269 /* 270 * The feholdexcept() function saves the current floating-point environment 271 * in the object pointed to by envp, clears the floating-point status flags, and 272 * then installs a non-stop (continue on floating-point exceptions) mode, if 273 * available, for all floating-point exceptions. 274 */ 275 int 276 feholdexcept(fenv_t *envp) 277 { 278 unsigned int mxcsr; 279 280 /* Store the current x87 floating-point environment */ 281 __asm__ volatile ("fnstenv %0" : "=m" (*envp)); 282 283 /* Clear all exception flags in FPU */ 284 __asm__ volatile ("fnclex"); 285 286 /* Store the MXCSR register state */ 287 __asm__ volatile ("stmxcsr %0" : "=m" (envp->__mxcsr)); 288 289 /* Clear exception flags in MXCSR */ 290 mxcsr = envp->__mxcsr; 291 mxcsr &= ~FE_ALL_EXCEPT; 292 293 /* Mask all exceptions */ 294 mxcsr |= FE_ALL_EXCEPT << _SSE_MASK_SHIFT; 295 296 /* Store the MXCSR register */ 297 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 298 299 return (0); 300 } 301 302 /* 303 * The fesetenv() function attempts to establish the floating-point environment 304 * represented by the object pointed to by envp. The argument `envp' points 305 * to an object set by a call to fegetenv() or feholdexcept(), or equal a 306 * floating-point environment macro. The fesetenv() function does not raise 307 * floating-point exceptions, but only installs the state of the floating-point 308 * status flags represented through its argument. 309 */ 310 int 311 fesetenv(const fenv_t *envp) 312 { 313 /* Load the x87 floating-point environent */ 314 __asm__ volatile ("fldenv %0" : : "m" (*envp)); 315 316 /* Store the MXCSR register */ 317 __asm__ volatile ("ldmxcsr %0" : : "m" (envp->__mxcsr)); 318 319 return (0); 320 } 321 322 /* 323 * The feupdateenv() function saves the currently raised floating-point 324 * exceptions in its automatic storage, installs the floating-point environment 325 * represented by the object pointed to by `envp', and then raises the saved 326 * floating-point exceptions. The argument `envp' shall point to an object set 327 * by a call to feholdexcept() or fegetenv(), or equal a floating-point 328 * environment macro. 329 */ 330 int 331 feupdateenv(const fenv_t *envp) 332 { 333 unsigned short status; 334 unsigned int mxcsr; 335 336 /* Store the x87 status register */ 337 __asm__ volatile ("fnstsw %0" : "=am" (status)); 338 339 /* Store the MXCSR register */ 340 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 341 342 /* Install new floating-point environment */ 343 fesetenv(envp); 344 345 /* Raise any previously accumulated exceptions */ 346 feraiseexcept(status | mxcsr); 347 348 return (0); 349 } 350 351 /* 352 * The following functions are extentions to the standard 353 */ 354 int 355 feenableexcept(int mask) 356 { 357 unsigned int mxcsr, omask; 358 unsigned short control; 359 360 mask &= FE_ALL_EXCEPT; 361 362 __asm__ volatile ("fnstcw %0" : "=m" (control)); 363 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 364 365 omask = ~(control | (mxcsr >> _SSE_MASK_SHIFT)) & FE_ALL_EXCEPT; 366 control &= ~mask; 367 __asm__ volatile ("fldcw %0" : : "m" (control)); 368 369 mxcsr &= ~(mask << _SSE_MASK_SHIFT); 370 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 371 372 return (omask); 373 } 374 375 int 376 fedisableexcept(int mask) 377 { 378 unsigned int mxcsr, omask; 379 unsigned short control; 380 381 mask &= FE_ALL_EXCEPT; 382 383 __asm__ volatile ("fnstcw %0" : "=m" (control)); 384 __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); 385 386 omask = ~(control | (mxcsr >> _SSE_MASK_SHIFT)) & FE_ALL_EXCEPT; 387 control |= mask; 388 __asm__ volatile ("fldcw %0" : : "m" (control)); 389 390 mxcsr |= mask << _SSE_MASK_SHIFT; 391 __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); 392 393 return (omask); 394 } 395 396 int 397 fegetexcept(void) 398 { 399 unsigned short control; 400 401 /* 402 * We assume that the masks for the x87 and the SSE unit are 403 * the same. 404 */ 405 __asm__ volatile ("fnstcw %0" : "=m" (control)); 406 407 return (~control & FE_ALL_EXCEPT); 408 } 409