1  /* Install given floating-point environment.
       2     Copyright (C) 2001-2023 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     <https://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)