sysdeps/x86_64/fpu/fesetenv.c

   1 /* Install given floating-point environment.
   2    Copyright (C) 2001-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <fenv.h>
  20 #include <fpu_control.h>
  21 #include <assert.h>
  22
  23
  24 /* All exceptions, including the x86-specific "denormal operand"
  25    exception.  */
  26 #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
  27
  28
  29 int
  30 __fesetenv (const fenv_t *envp)
  31 {
  32   fenv_t temp;
  33
  34   /* Install the environment specified by ENVP.  But there are a few
  35      values which we do not want to come from the saved environment.
  36      Therefore, we get the current environment and replace the values
  37      we want to use from the environment specified by the parameter.  */
  38   __asm__ ("fnstenv %0\n"
  39            "stmxcsr %1" : "=m" (*&temp), "=m" (*&temp.__mxcsr));
  40
  41   if (envp == FE_DFL_ENV)
  42     {
  43       temp.__control_word |= FE_ALL_EXCEPT_X86;
  44       temp.__control_word &= ~FE_TOWARDZERO;
  45       temp.__control_word |= _FPU_EXTENDED;
  46       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  47       temp.__eip = 0;
  48       temp.__cs_selector = 0;
  49       temp.__opcode = 0;
  50       temp.__data_offset = 0;
  51       temp.__data_selector = 0;
  52       /* Clear SSE exceptions.  */
  53       temp.__mxcsr &= ~FE_ALL_EXCEPT_X86;
  54       /* Set mask for SSE MXCSR.  */
  55       temp.__mxcsr |= (FE_ALL_EXCEPT_X86 << 7);
  56       /* Set rounding to FE_TONEAREST.  */
  57       temp.__mxcsr &= ~ 0x6000;
  58       temp.__mxcsr |= (FE_TONEAREST << 3);
  59       /* Clear the FZ and DAZ bits.  */
  60       temp.__mxcsr &= ~0x8040;
  61     }
  62   else if (envp == FE_NOMASK_ENV)
  63     {
  64       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
  65       /* Keep the "denormal operand" exception masked.  */
  66       temp.__control_word |= __FE_DENORM;
  67       temp.__control_word |= _FPU_EXTENDED;
  68       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  69       temp.__eip = 0;
  70       temp.__cs_selector = 0;
  71       temp.__opcode = 0;
  72       temp.__data_offset = 0;
  73       temp.__data_selector = 0;
  74       /* Clear SSE exceptions.  */
  75       temp.__mxcsr &= ~FE_ALL_EXCEPT_X86;
  76       /* Set mask for SSE MXCSR.  */
  77       /* Set rounding to FE_TONEAREST.  */
  78       temp.__mxcsr &= ~ 0x6000;
  79       temp.__mxcsr |= (FE_TONEAREST << 3);
  80       /* Do not mask exceptions.  */
  81       temp.__mxcsr &= ~(FE_ALL_EXCEPT << 7);
  82       /* Keep the "denormal operand" exception masked.  */
  83       temp.__mxcsr |= (__FE_DENORM << 7);
  84       /* Clear the FZ and DAZ bits.  */
  85       temp.__mxcsr &= ~0x8040;
  86     }
  87   else
  88     {
  89       temp.__control_word &= ~(FE_ALL_EXCEPT_X86
  90                                | FE_TOWARDZERO
  91                                | _FPU_EXTENDED);
  92       temp.__control_word |= (envp->__control_word
  93                               & (FE_ALL_EXCEPT_X86
  94                                  | FE_TOWARDZERO
  95                                  | _FPU_EXTENDED));
  96       temp.__status_word &= ~FE_ALL_EXCEPT_X86;
  97       temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT_X86;
  98       temp.__eip = envp->__eip;
  99       temp.__cs_selector = envp->__cs_selector;
 100       temp.__opcode = envp->__opcode;
 101       temp.__data_offset = envp->__data_offset;
 102       temp.__data_selector = envp->__data_selector;
 103       temp.__mxcsr = envp->__mxcsr;
 104     }
 105
 106   __asm__ ("fldenv %0\n"
 107            "ldmxcsr %1" : : "m" (temp), "m" (temp.__mxcsr));
 108
 109   /* Success.  */
 110   return 0;
 111 }
 112 libm_hidden_def (__fesetenv)
 113 weak_alias (__fesetenv, fesetenv)
 114 libm_hidden_weak (fesetenv)