fenv.c revision 1.6
1 /* $NetBSD: fenv.c,v 1.6 2013/11/11 00:31:51 joerg Exp $ */ 2 3 /*- 4 * Copyright (c) 2004-2005 David Schultz <das (at) 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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __RCSID("$NetBSD: fenv.c,v 1.6 2013/11/11 00:31:51 joerg Exp $"); 31 32 #include <sys/param.h> 33 #include <sys/sysctl.h> 34 #include <assert.h> 35 #include <fenv.h> 36 #include <stddef.h> 37 #include <string.h> 38 39 /* Load x87 Control Word */ 40 #define __fldcw(__cw) __asm__ __volatile__ \ 41 ("fldcw %0" : : "m" (__cw)) 42 43 /* No-Wait Store Control Word */ 44 #define __fnstcw(__cw) __asm__ __volatile__ \ 45 ("fnstcw %0" : "=m" (*(__cw))) 46 47 /* No-Wait Store Status Word */ 48 #define __fnstsw(__sw) __asm__ __volatile__ \ 49 ("fnstsw %0" : "=am" (*(__sw))) 50 51 /* No-Wait Clear Exception Flags */ 52 #define __fnclex() __asm__ __volatile__ \ 53 ("fnclex") 54 55 /* Load x87 Environment */ 56 #define __fldenv(__env) __asm__ __volatile__ \ 57 ("fldenv %0" : : "m" (__env)) 58 59 /* No-Wait Store x87 environment */ 60 #define __fnstenv(__env) __asm__ __volatile__ \ 61 ("fnstenv %0" : "=m" (*(__env))) 62 63 /* Check for and handle pending unmasked x87 pending FPU exceptions */ 64 #define __fwait(__env) __asm__ __volatile__ \ 65 ("fwait") 66 67 /* Load the MXCSR register */ 68 #define __ldmxcsr(__mxcsr) __asm__ __volatile__ \ 69 ("ldmxcsr %0" : : "m" (__mxcsr)) 70 71 /* Store the MXCSR register state */ 72 #define __stmxcsr(__mxcsr) __asm__ __volatile__ \ 73 ("stmxcsr %0" : "=m" (*(__mxcsr))) 74 75 /* 76 * The following constant represents the default floating-point environment 77 * (that is, the one installed at program startup) and has type pointer to 78 * const-qualified fenv_t. 79 * 80 * It can be used as an argument to the functions within the <fenv.h> header 81 * that manage the floating-point environment, namely fesetenv() and 82 * feupdateenv(). 83 * 84 * x87 fpu registers are 16bit wide. The upper bits, 31-16, are marked as 85 * RESERVED. We provide a partial floating-point environment, where we 86 * define only the lower bits. The reserved bits are extracted and set by the 87 * consumers of FE_DFL_ENV, during runtime. 88 */ 89 fenv_t __fe_dfl_env = { 90 { 91 __NetBSD_NPXCW__, /* Control word register */ 92 0x0, /* Unused */ 93 0x0000, /* Status word register */ 94 0x0, /* Unused */ 95 0x0000ffff, /* Tag word register */ 96 0x0, /* Unused */ 97 { 98 0x0000, 0x0000, 99 0x0000, 0xffff 100 } 101 }, 102 __INITIAL_MXCSR__ /* MXCSR register */ 103 }; 104 105 /* 106 * Test for SSE support on this processor. 107 * 108 * We need to use ldmxcsr/stmxcsr to get correct results if any part 109 * of the program was compiled to use SSE floating-point, but we can't 110 * use SSE on older processors. 111 * 112 * In order to do so, we need to query the processor capabilities via the CPUID 113 * instruction. We can make it even simpler though, by querying the machdep.sse 114 * sysctl. 115 */ 116 static int __HAS_SSE = 0; 117 118 static void __init_libm(void) __attribute__ ((constructor, used)); 119 120 static void __init_libm(void) 121 { 122 size_t oldlen = sizeof(__HAS_SSE); 123 int rv; 124 uint16_t control; 125 126 rv = sysctlbyname("machdep.sse", &__HAS_SSE, &oldlen, NULL, 0); 127 if (rv == -1) 128 __HAS_SSE = 0; 129 130 __fnstcw(&control); 131 __fe_dfl_env.x87.control = control; 132 } 133 134 /* 135 * The feclearexcept() function clears the supported floating-point exceptions 136 * represented by `excepts'. 137 */ 138 int 139 feclearexcept(int excepts) 140 { 141 fenv_t env; 142 uint32_t mxcsr; 143 int ex; 144 145 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); 146 147 ex = excepts & FE_ALL_EXCEPT; 148 149 /* It's ~3x faster to call fnclex, than store/load fp env */ 150 if (ex == FE_ALL_EXCEPT) { 151 __fnclex(); 152 } else { 153 __fnstenv(&env); 154 env.x87.status &= ~ex; 155 __fldenv(env); 156 } 157 158 if (__HAS_SSE) { 159 __stmxcsr(&mxcsr); 160 mxcsr &= ~ex; 161 __ldmxcsr(mxcsr); 162 } 163 164 /* Success */ 165 return (0); 166 } 167 168 /* 169 * The fegetexceptflag() function stores an implementation-defined 170 * representation of the states of the floating-point status flags indicated by 171 * the argument excepts in the object pointed to by the argument flagp. 172 */ 173 int 174 fegetexceptflag(fexcept_t *flagp, int excepts) 175 { 176 uint32_t mxcsr; 177 uint16_t status; 178 int ex; 179 180 _DIAGASSERT(flagp != NULL); 181 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); 182 183 ex = excepts & FE_ALL_EXCEPT; 184 185 __fnstsw(&status); 186 if (__HAS_SSE) 187 __stmxcsr(&mxcsr); 188 else 189 mxcsr = 0; 190 191 *flagp = (mxcsr | status) & ex; 192 193 /* Success */ 194 return (0); 195 } 196 197 /* 198 * The feraiseexcept() function raises the supported floating-point exceptions 199 * represented by the argument `excepts'. 200 * 201 * The standard explicitly allows us to execute an instruction that has the 202 * exception as a side effect, but we choose to manipulate the status register 203 * directly. 204 * 205 * The validation of input is being deferred to fesetexceptflag(). 206 */ 207 int 208 feraiseexcept(int excepts) 209 { 210 fexcept_t ex; 211 212 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); 213 214 ex = excepts & FE_ALL_EXCEPT; 215 fesetexceptflag(&ex, excepts); 216 __fwait(); 217 218 /* Success */ 219 return (0); 220 } 221 222 /* 223 * This function sets the floating-point status flags indicated by the argument 224 * `excepts' to the states stored in the object pointed to by `flagp'. It does 225 * NOT raise any floating-point exceptions, but only sets the state of the flags. 226 */ 227 int 228 fesetexceptflag(const fexcept_t *flagp, int excepts) 229 { 230 fenv_t env; 231 uint32_t mxcsr; 232 int ex; 233 234 _DIAGASSERT(flagp != NULL); 235 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); 236 237 ex = excepts & FE_ALL_EXCEPT; 238 239 __fnstenv(&env); 240 env.x87.status &= ~ex; 241 env.x87.status |= *flagp & ex; 242 __fldenv(env); 243 244 if (__HAS_SSE) { 245 __stmxcsr(&mxcsr); 246 mxcsr &= ~ex; 247 mxcsr |= *flagp & ex; 248 __ldmxcsr(mxcsr); 249 } 250 251 /* Success */ 252 return (0); 253 } 254 255 /* 256 * The fetestexcept() function determines which of a specified subset of the 257 * floating-point exception flags are currently set. The `excepts' argument 258 * specifies the floating-point status flags to be queried. 259 */ 260 int 261 fetestexcept(int excepts) 262 { 263 uint32_t mxcsr; 264 uint16_t status; 265 int ex; 266 267 _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); 268 269 ex = excepts & FE_ALL_EXCEPT; 270 271 __fnstsw(&status); 272 if (__HAS_SSE) 273 __stmxcsr(&mxcsr); 274 else 275 mxcsr = 0; 276 277 return ((status | mxcsr) & ex); 278 } 279 280 int 281 fegetround(void) 282 { 283 uint16_t control; 284 285 /* 286 * We assume that the x87 and the SSE unit agree on the 287 * rounding mode. Reading the control word on the x87 turns 288 * out to be about 5 times faster than reading it on the SSE 289 * unit on an Opteron 244. 290 */ 291 __fnstcw(&control); 292 293 return (control & __X87_ROUND_MASK); 294 } 295 296 /* 297 * The fesetround() function shall establish the rounding direction represented 298 * by its argument round. If the argument is not equal to the value of a 299 * rounding direction macro, the rounding direction is not changed. 300 */ 301 int 302 fesetround(int round) 303 { 304 uint32_t mxcsr; 305 uint16_t control; 306 307 if (round & ~__X87_ROUND_MASK) { 308 /* Failure */ 309 return (-1); 310 } 311 312 __fnstcw(&control); 313 control &= ~__X87_ROUND_MASK; 314 control |= round; 315 __fldcw(control); 316 317 if (__HAS_SSE) { 318 __stmxcsr(&mxcsr); 319 mxcsr &= ~(__X87_ROUND_MASK << __SSE_ROUND_SHIFT); 320 mxcsr |= round << __SSE_ROUND_SHIFT; 321 __ldmxcsr(mxcsr); 322 } 323 324 /* Success */ 325 return (0); 326 } 327 328 /* 329 * The fegetenv() function attempts to store the current floating-point 330 * environment in the object pointed to by envp. 331 */ 332 int 333 fegetenv(fenv_t *envp) 334 { 335 uint32_t mxcsr; 336 337 _DIAGASSERT(flagp != NULL); 338 339 /* 340 * fnstenv masks all exceptions, so we need to restore the old control 341 * word to avoid this side effect. 342 */ 343 __fnstenv(envp); 344 __fldcw(envp->x87.control); 345 if (__HAS_SSE) { 346 __stmxcsr(&mxcsr); 347 envp->mxcsr = mxcsr; 348 } 349 350 /* Success */ 351 return (0); 352 } 353 354 /* 355 * The feholdexcept() function saves the current floating-point environment in 356 * the object pointed to by envp, clears the floating-point status flags, and 357 * then installs a non-stop (continue on floating-point exceptions) mode, if 358 * available, for all floating-point exceptions. 359 */ 360 int 361 feholdexcept(fenv_t *envp) 362 { 363 uint32_t mxcsr; 364 365 _DIAGASSERT(envp != NULL); 366 367 __fnstenv(envp); 368 __fnclex(); 369 if (__HAS_SSE) { 370 __stmxcsr(&mxcsr); 371 envp->mxcsr = mxcsr; 372 mxcsr &= ~FE_ALL_EXCEPT; 373 mxcsr |= FE_ALL_EXCEPT << __SSE_EMASK_SHIFT; 374 __ldmxcsr(mxcsr); 375 } 376 377 /* Success */ 378 return (0); 379 } 380 381 /* 382 * The fesetenv() function attempts to establish the floating-point environment 383 * represented by the object pointed to by envp. The argument `envp' points 384 * to an object set by a call to fegetenv() or feholdexcept(), or equal a 385 * floating-point environment macro. The fesetenv() function does not raise 386 * floating-point exceptions, but only installs the state of the floating-point 387 * status flags represented through its argument. 388 */ 389 int 390 fesetenv(const fenv_t *envp) 391 { 392 fenv_t env; 393 394 _DIAGASSERT(envp != NULL); 395 396 /* Store the x87 floating-point environment */ 397 memset(&env, 0, sizeof(env)); 398 __fnstenv(&env); 399 400 __fe_dfl_env.x87.unused1 = env.x87.unused1; 401 __fe_dfl_env.x87.unused2 = env.x87.unused2; 402 __fe_dfl_env.x87.unused3 = env.x87.unused3; 403 memcpy(__fe_dfl_env.x87.others, 404 env.x87.others, 405 sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t)); 406 407 __fldenv(envp->x87); 408 if (__HAS_SSE) 409 __ldmxcsr(envp->mxcsr); 410 411 /* Success */ 412 return (0); 413 } 414 415 /* 416 * The feupdateenv() function saves the currently raised floating-point 417 * exceptions in its automatic storage, installs the floating-point environment 418 * represented by the object pointed to by `envp', and then raises the saved 419 * floating-point exceptions. The argument `envp' shall point to an object set 420 * by a call to feholdexcept() or fegetenv(), or equal a floating-point 421 * environment macro. 422 */ 423 int 424 feupdateenv(const fenv_t *envp) 425 { 426 fenv_t env; 427 uint32_t mxcsr; 428 uint16_t status; 429 430 _DIAGASSERT(envp != NULL); 431 432 /* Store the x87 floating-point environment */ 433 memset(&env, 0, sizeof(env)); 434 __fnstenv(&env); 435 436 __fe_dfl_env.x87.unused1 = env.x87.unused1; 437 __fe_dfl_env.x87.unused2 = env.x87.unused2; 438 __fe_dfl_env.x87.unused3 = env.x87.unused3; 439 memcpy(__fe_dfl_env.x87.others, 440 env.x87.others, 441 sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t)); 442 443 __fnstsw(&status); 444 if (__HAS_SSE) 445 __stmxcsr(&mxcsr); 446 else 447 mxcsr = 0; 448 fesetenv(envp); 449 feraiseexcept((mxcsr | status) & FE_ALL_EXCEPT); 450 451 /* Success */ 452 return (0); 453 } 454 455 /* 456 * The following functions are extentions to the standard 457 */ 458 int 459 feenableexcept(int mask) 460 { 461 uint32_t mxcsr, omask; 462 uint16_t control; 463 464 mask &= FE_ALL_EXCEPT; 465 __fnstcw(&control); 466 if (__HAS_SSE) 467 __stmxcsr(&mxcsr); 468 else 469 mxcsr = 0; 470 471 omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT; 472 control &= ~mask; 473 __fldcw(control); 474 if (__HAS_SSE) { 475 mxcsr &= ~(mask << __SSE_EMASK_SHIFT); 476 __ldmxcsr(mxcsr); 477 } 478 479 return (FE_ALL_EXCEPT & ~omask); 480 } 481 482 int 483 fedisableexcept(int mask) 484 { 485 uint32_t mxcsr, omask; 486 uint16_t control; 487 488 mask &= FE_ALL_EXCEPT; 489 __fnstcw(&control); 490 if (__HAS_SSE) 491 __stmxcsr(&mxcsr); 492 else 493 mxcsr = 0; 494 495 omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT; 496 control |= mask; 497 __fldcw(control); 498 if (__HAS_SSE) { 499 mxcsr |= mask << __SSE_EMASK_SHIFT; 500 __ldmxcsr(mxcsr); 501 } 502 503 return (FE_ALL_EXCEPT & ~omask); 504 } 505 506 int 507 fegetexcept(void) 508 { 509 uint16_t control; 510 511 /* 512 * We assume that the masks for the x87 and the SSE unit are 513 * the same. 514 */ 515 __fnstcw(&control); 516 517 return (~control & FE_ALL_EXCEPT); 518 } 519
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