sysdeps/i386/fpu/fesetenv.c

   1 /* Install given floating-point environment.
   2    Copyright (C) 1997-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <fenv.h>
  21 #include <fpu_control.h>
  22 #include <assert.h>
  23 #include <unistd.h>
  24 #include <ldsodefs.h>
  25 #include <dl-procinfo.h>
  26
  27
  28 /* All exceptions, including the x86-specific "denormal operand"
  29    exception.  */
  30 #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
  31
  32
  33 int
  34 __fesetenv (const fenv_t *envp)
  35 {
  36   fenv_t temp;
  37
  38   /* The memory block used by fstenv/fldenv has a size of 28 bytes.  */
  39   assert (sizeof (fenv_t) == 28);
  40
  41   /* Install the environment specified by ENVP.  But there are a few
  42      values which we do not want to come from the saved environment.
  43      Therefore, we get the current environment and replace the values
  44      we want to use from the environment specified by the parameter.  */
  45   __asm__ ("fnstenv %0" : "=m" (*&temp));
  46
  47   if (envp == FE_DFL_ENV)
  48     {
  49       temp.__control_word |= FE_ALL_EXCEPT_X86;
  50       temp.__control_word &= ~FE_TOWARDZERO;
  51       temp.__control_word |= _FPU_EXTENDED;
  52       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  53     }
  54   else if (envp == FE_NOMASK_ENV)
  55     {
  56       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
  57       /* Keep the "denormal operand" exception masked.  */
  58       temp.__control_word |= __FE_DENORM;
  59       temp.__control_word |= _FPU_EXTENDED;
  60       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  61     }
  62   else
  63     {
  64       temp.__control_word &= ~(FE_ALL_EXCEPT_X86
  65                                | FE_TOWARDZERO
  66                                | _FPU_EXTENDED);
  67       temp.__control_word |= (envp->__control_word
  68                               & (FE_ALL_EXCEPT_X86
  69                                  | FE_TOWARDZERO
  70                                  | _FPU_EXTENDED));
  71       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  72       temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT_X86;
  73     }
  74   temp.__eip = 0;
  75   temp.__cs_selector = 0;
  76   temp.__opcode = 0;
  77   temp.__data_offset = 0;
  78   temp.__data_selector = 0;
  79
  80   __asm__ ("fldenv %0" : : "m" (temp));
  81
  82   if (HAS_CPU_FEATURE (SSE))
  83     {
  84       unsigned int mxcsr;
  85       __asm__ ("stmxcsr %0" : "=m" (mxcsr));
  86
  87       if (envp == FE_DFL_ENV)
  88         {
  89           /* Clear SSE exceptions.  */
  90           mxcsr &= ~FE_ALL_EXCEPT_X86;
  91           /* Set mask for SSE MXCSR.  */
  92           mxcsr |= (FE_ALL_EXCEPT_X86 << 7);
  93           /* Set rounding to FE_TONEAREST.  */
  94           mxcsr &= ~0x6000;
  95           mxcsr |= (FE_TONEAREST << 3);
  96           /* Clear the FZ and DAZ bits.  */
  97           mxcsr &= ~0x8040;
  98         }
  99       else if (envp == FE_NOMASK_ENV)
 100         {
 101           /* Clear SSE exceptions.  */
 102           mxcsr &= ~FE_ALL_EXCEPT_X86;
 103           /* Do not mask exceptions.  */
 104           mxcsr &= ~(FE_ALL_EXCEPT << 7);
 105           /* Keep the "denormal operand" exception masked.  */
 106           mxcsr |= (__FE_DENORM << 7);
 107           /* Set rounding to FE_TONEAREST.  */
 108           mxcsr &= ~0x6000;
 109           mxcsr |= (FE_TONEAREST << 3);
 110           /* Clear the FZ and DAZ bits.  */
 111           mxcsr &= ~0x8040;
 112         }
 113       else
 114         mxcsr = envp->__eip;
 115
 116       __asm__ ("ldmxcsr %0" : : "m" (mxcsr));
 117     }
 118
 119   /* Success.  */
 120   return 0;
 121 }
 122
 123 #include <shlib-compat.h>
 124 #if SHLIB_COMPAT (libm, GLIBC_2_1, GLIBC_2_2)
 125 strong_alias (__fesetenv, __old_fesetenv)
 126 compat_symbol (libm, __old_fesetenv, fesetenv, GLIBC_2_1);
 127 #endif
 128
 129 libm_hidden_def (__fesetenv)
 130 libm_hidden_ver (__fesetenv, fesetenv)
 131 versioned_symbol (libm, __fesetenv, fesetenv, GLIBC_2_2);