lib/fenv-except-tracking-raise.c

   1 /* Functions for tracking which floating-point exceptions have occurred.
   2    Copyright (C) 1997-2025 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Based on glibc/sysdeps/<cpu>/{fclrexcpt.c,fraiseexcpt.c,ftestexcept.c}
  18    together with glibc/sysdeps/<cpu>/{fpu_control.h,fenv_private.h,fenv_libc.h}.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <fenv.h>
  24
  25 #include "fenv-private.h"
  26
  27 _GL_UNUSED static void
  28 generic_feraiseexcept (int exceptions)
  29 {
  30   /* First: invalid exception.  */
  31   if (exceptions & FE_INVALID)
  32     {
  33       double volatile a;
  34       _GL_UNUSED double volatile b;
  35       a = 0; b = a / a;
  36     }
  37   /* Next: division by zero.  */
  38   if (exceptions & FE_DIVBYZERO)
  39     {
  40       double volatile a, b;
  41       _GL_UNUSED double volatile c;
  42       a = 1; b = 0; c = a / b;
  43     }
  44   /* Next: overflow.  */
  45   if (exceptions & FE_OVERFLOW)
  46     {
  47       double volatile a;
  48       _GL_UNUSED double volatile b;
  49       a = 1e200; b = a * a;
  50     }
  51   /* Next: underflow.  */
  52   if (exceptions & FE_UNDERFLOW)
  53     {
  54       double volatile a;
  55       _GL_UNUSED double volatile b;
  56       a = 1e-200; b = a * a;
  57     }
  58   /* Last: inexact.  */
  59   if (exceptions & FE_INEXACT)
  60     {
  61       double volatile a, b;
  62       _GL_UNUSED double volatile c;
  63       a = 1; b = 3; c = a / b;
  64     }
  65 }
  66
  67 #if defined __GNUC__ || defined __clang__ || defined _MSC_VER
  68
  69 # if (defined __x86_64__ || defined _M_X64) || (defined __i386 || defined _M_IX86)
  70
  71 int
  72 feraiseexcept (int exceptions)
  73 {
  74 #  if defined _MSC_VER
  75
  76   /* Setting the exception flags only in the SSE unit (i.e. in the mxcsr
  77      register) would not cause the hardware to trap on the exception.  */
  78   generic_feraiseexcept (exceptions);
  79
  80 #  else
  81
  82   exceptions &= FE_ALL_EXCEPT;
  83
  84   if ((exceptions & ~(FE_INVALID | FE_DIVBYZERO)) == 0)
  85     {
  86       /* Like generic_feraiseexcept (exceptions).  */
  87       /* This code is probably faster than the general code below.  */
  88       /* First: invalid exception.  */
  89       if (exceptions & FE_INVALID)
  90         {
  91           double volatile a;
  92           _GL_UNUSED double volatile b;
  93           a = 0; b = a / a;
  94         }
  95       /* Next: division by zero.  */
  96       if (exceptions & FE_DIVBYZERO)
  97         {
  98           double volatile a, b;
  99           _GL_UNUSED double volatile c;
 100           a = 1; b = 0; c = a / b;
 101         }
 102     }
 103   else
 104     {
 105       /* The general case.  */
 106
 107       /* Set the bits in the 387 unit.  */
 108       x86_387_fenv_t env;
 109       __asm__ __volatile__ ("fnstenv %0" : "=m" (*&env));
 110       /* Note: fnstenv masks all floating-point exceptions until the fldenv
 111          below.  */
 112       env.__status_word |= exceptions;
 113       __asm__ __volatile__ ("fldenv %0" : : "m" (*&env));
 114       /* A trap (if enabled) is triggered only at the next floating-point
 115          instruction.  Force it to occur here.  */
 116       __asm__ __volatile__ ("fwait");
 117     }
 118
 119 #  endif
 120   return 0;
 121 }
 122
 123 # elif defined __aarch64__ /* arm64 */
 124
 125 int
 126 feraiseexcept (int exceptions)
 127 {
 128 #  if 0
 129   /* This would just set the flag bits and make fetestexcept() work as expected.
 130      But it would not cause the hardware to trap on the exception.  */
 131   exceptions &= FE_ALL_EXCEPT;
 132
 133   unsigned long fpsr, orig_fpsr;
 134   _FPU_GETFPSR (orig_fpsr);
 135   fpsr = orig_fpsr | exceptions;
 136   if (fpsr != orig_fpsr)
 137     _FPU_SETFPSR (fpsr);
 138 #  else
 139   /* This is how glibc does it.
 140      The drawback is that when FE_OVERFLOW is raised, FE_INEXACT is raised
 141      with it.  */
 142   generic_feraiseexcept (exceptions);
 143 #  endif
 144   return 0;
 145 }
 146
 147 # elif defined __arm__
 148
 149 int
 150 feraiseexcept (int exceptions)
 151 {
 152 #  ifdef __SOFTFP__
 153   exceptions &= FE_ALL_EXCEPT;
 154
 155   if (exceptions != 0)
 156     return -1;
 157 #  else
 158   /* Raise exceptions represented by EXCEPTIONS.  But we must raise only
 159      one signal at a time.  It is important that if the overflow/underflow
 160      exception and the inexact exception are given at the same time,
 161      the overflow/underflow exception follows the inexact exception.  After
 162      each exception we read from the fpscr, to force the exception to be
 163      raised immediately.  */
 164   /* XXX Probably this should do actual floating-point operations, like in
 165      generic_feraiseexcept, not just setting flag bits in the fpscr.  */
 166   unsigned int fpscr, orig_fpscr;
 167   /* First: invalid exception.  */
 168   if (exceptions & FE_INVALID)
 169     {
 170       _FPU_GETCW (orig_fpscr);
 171       fpscr = orig_fpscr | FE_INVALID;
 172       if (fpscr != orig_fpscr)
 173         {
 174           _FPU_SETCW (fpscr);
 175           _FPU_GETCW (fpscr);
 176         }
 177     }
 178   /* Next: division by zero.  */
 179   if (exceptions & FE_DIVBYZERO)
 180     {
 181       _FPU_GETCW (orig_fpscr);
 182       fpscr = orig_fpscr | FE_DIVBYZERO;
 183       if (fpscr != orig_fpscr)
 184         {
 185           _FPU_SETCW (fpscr);
 186           _FPU_GETCW (fpscr);
 187         }
 188     }
 189   /* Next: overflow.  */
 190   if (exceptions & FE_OVERFLOW)
 191     {
 192       _FPU_GETCW (orig_fpscr);
 193       fpscr = orig_fpscr | FE_OVERFLOW;
 194       if (fpscr != orig_fpscr)
 195         {
 196           _FPU_SETCW (fpscr);
 197           _FPU_GETCW (fpscr);
 198         }
 199     }
 200   /* Next: underflow.  */
 201   if (exceptions & FE_UNDERFLOW)
 202     {
 203       _FPU_GETCW (orig_fpscr);
 204       fpscr = orig_fpscr | FE_UNDERFLOW;
 205       if (fpscr != orig_fpscr)
 206         {
 207           _FPU_SETCW (fpscr);
 208           _FPU_GETCW (fpscr);
 209         }
 210     }
 211   /* Last: inexact.  */
 212   if (exceptions & FE_INEXACT)
 213     {
 214       _FPU_GETCW (orig_fpscr);
 215       fpscr = orig_fpscr | FE_INEXACT;
 216       if (fpscr != orig_fpscr)
 217         {
 218           _FPU_SETCW (fpscr);
 219           _FPU_GETCW (fpscr);
 220         }
 221     }
 222 #  endif
 223   return 0;
 224 }
 225
 226 # elif defined __alpha
 227
 228 /* Prefer the Linux system call when available.
 229    See glibc/sysdeps/unix/sysv/linux/alpha/fraiseexcpt.S  */
 230 #  if !defined __linux__
 231 int
 232 feraiseexcept (int exceptions)
 233 {
 234   /* This implementation cannot raise FE_INEXACT.  */
 235   generic_feraiseexcept (exceptions);
 236   return 0;
 237 }
 238 #  endif
 239
 240 # elif defined __hppa
 241
 242 int
 243 feraiseexcept (int exceptions)
 244 {
 245   generic_feraiseexcept (exceptions);
 246   return 0;
 247 }
 248
 249 # elif defined __ia64__
 250
 251 int
 252 feraiseexcept (int exceptions)
 253 {
 254   /* Raise exceptions represented by EXCEPTIONS.  But we must raise only
 255      one signal at a time.  It is important that if the overflow/underflow
 256      exception and the inexact exception are given at the same time,
 257      the overflow/underflow exception precedes the inexact exception.  */
 258   generic_feraiseexcept (exceptions);
 259   return 0;
 260 }
 261
 262 # elif defined __m68k__
 263
 264 int
 265 feraiseexcept (int exceptions)
 266 {
 267   generic_feraiseexcept (exceptions);
 268   return 0;
 269 }
 270
 271 # elif defined __mips__
 272
 273 int
 274 feraiseexcept (int exceptions)
 275 {
 276   exceptions &= FE_ALL_EXCEPT;
 277
 278   /* Set also the cause bits.  The setting of the cause bits is what actually
 279      causes the hardware to trap on the exception, if the corresponding enable
 280      bit is set as well.  */
 281   unsigned int fcsr, orig_fcsr;
 282   _FPU_GETCW (orig_fcsr);
 283   fcsr = orig_fcsr | ((exceptions << 10) | exceptions);
 284   if (fcsr != orig_fcsr)
 285     _FPU_SETCW (fcsr);
 286
 287   return 0;
 288 }
 289
 290 # elif defined __loongarch__
 291
 292 int
 293 feraiseexcept (int exceptions)
 294 {
 295 #  if 0
 296   /* This would just set the flag bits and make fetestexcept() work as expected.
 297      But it would not cause the hardware to trap on the exception.  */
 298   exceptions &= FE_ALL_EXCEPT;
 299
 300   /* Set also the cause bits.  The setting of the cause bits is what actually
 301      causes the hardware to trap on the exception, if the corresponding enable
 302      bit is set as well.  */
 303   unsigned int fcsr, orig_fcsr;
 304   _FPU_GETCW (orig_fcsr);
 305   fcsr = orig_fcsr | ((exceptions << 8) | exceptions);
 306   if (fcsr != orig_fcsr)
 307     _FPU_SETCW (fcsr);
 308 #  else
 309   /* This is how glibc does it.
 310      The drawback is that when FE_OVERFLOW is raised, FE_INEXACT is raised
 311      with it.  */
 312   generic_feraiseexcept (exceptions);
 313 #  endif
 314   return 0;
 315 }
 316
 317 # elif defined __powerpc__
 318
 319 int
 320 feraiseexcept (int exceptions)
 321 {
 322   exceptions &= FE_ALL_EXCEPT;
 323
 324   union { unsigned long long u; double f; } memenv, orig_memenv;
 325   _FPU_GETCW_AS_DOUBLE (memenv.f);
 326   orig_memenv = memenv;
 327
 328   /* Instead of setting FE_INVALID (= bit 29), we need to set one of the
 329      individual bits: bit 10 or, if that does not work, bit 24.  */
 330   memenv.u |= (exceptions & FE_INVALID
 331                ? (exceptions & ~FE_INVALID) | (1U << 10)
 332                : exceptions);
 333
 334   if (!(memenv.u == orig_memenv.u))
 335     {
 336       _FPU_SETCW_AS_DOUBLE (memenv.f);
 337       if (exceptions & FE_INVALID)
 338         {
 339           /* Did it work?  */
 340           _FPU_GETCW_AS_DOUBLE (memenv.f);
 341           if ((memenv.u & FE_INVALID) == 0)
 342             {
 343               memenv.u |= (1U << 24);
 344               _FPU_SETCW_AS_DOUBLE (memenv.f);
 345             }
 346         }
 347     }
 348
 349   return 0;
 350 }
 351
 352 # elif defined __riscv
 353
 354 int
 355 feraiseexcept (int exceptions)
 356 {
 357   exceptions &= FE_ALL_EXCEPT;
 358   __asm__ __volatile__ ("csrs fflags, %0" : : "r" (exceptions));
 359   return 0;
 360 }
 361
 362 # elif defined __s390__ || defined __s390x__
 363
 364 int
 365 feraiseexcept (int exceptions)
 366 {
 367   generic_feraiseexcept (exceptions);
 368   return 0;
 369 }
 370
 371 # elif defined __sh__
 372
 373 int
 374 feraiseexcept (int exceptions)
 375 {
 376 #  if 0
 377   /* This would just set the flag bits and make fetestexcept() work as expected.
 378      But it would not cause the hardware to trap on the exception.  */
 379   exceptions &= FE_ALL_EXCEPT;
 380
 381   unsigned int fpscr, orig_fpscr;
 382   _FPU_GETCW (orig_fpscr);
 383   fpscr = orig_fpscr | exceptions;
 384   if (fpscr != orig_fpscr)
 385     _FPU_SETCW (fpscr);
 386 #  else
 387   /* This is how glibc does it.
 388      The drawback is that when FE_OVERFLOW is raised, FE_INEXACT is raised
 389      with it.  */
 390   generic_feraiseexcept (exceptions);
 391 #  endif
 392   return 0;
 393 }
 394
 395 # elif defined __sparc
 396
 397 int
 398 feraiseexcept (int exceptions)
 399 {
 400 #  if 0
 401   /* This would just set the flag bits and make fetestexcept() work as expected.
 402      But it would not cause the hardware to trap on the exception.  */
 403   exceptions &= FE_ALL_EXCEPT;
 404
 405   unsigned long fsr, orig_fsr;
 406   _FPU_GETCW (orig_fsr);
 407 #   if FE_INEXACT == 32 /* glibc compatible FE_* values */
 408   fsr = orig_fsr | exceptions;
 409 #   else /* Solaris compatible FE_* values */
 410   fsr = orig_fsr | (exceptions << 5);
 411 #   endif
 412   if (fsr != orig_fsr)
 413     _FPU_SETCW (fsr);
 414 #  else
 415   /* This is how glibc does it.
 416      The drawback is that when FE_OVERFLOW is raised, FE_INEXACT is raised
 417      with it.  */
 418   generic_feraiseexcept (exceptions);
 419 #  endif
 420   return 0;
 421 }
 422
 423 # else
 424
 425 #  if defined __GNUC__ || defined __clang__
 426 #   warning "Unknown CPU / architecture. Please report your platform and compiler to <bug-gnulib@gnu.org>."
 427 #  endif
 428 #  define NEED_FALLBACK 1
 429
 430 # endif
 431
 432 #else
 433
 434 /* The compiler does not support __asm__ statements or equivalent
 435    intrinsics.  */
 436
 437 # define NEED_FALLBACK 1
 438
 439 #endif
 440
 441 #if NEED_FALLBACK
 442
 443 /* A fallback that should work everywhere.  */
 444
 445 int
 446 feraiseexcept (int exceptions)
 447 {
 448   generic_feraiseexcept (exceptions);
 449   return 0;
 450 }
 451
 452 #endif