libm/x86_64/fesetmode.c

   1 /* Install given floating-point control modes.  x86_64 version.
   2    Copyright (C) 2016-2017 Free Software Foundation, Inc.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <fenv.h>
  19 #include <fpu_control.h>
  20
  21 /* All exceptions, including the x86-specific "denormal operand"
  22    exception.  */
  23 #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
  24
  25 int
  26 fesetmode (const femode_t *modep)
  27 {
  28   fpu_control_t cw;
  29   unsigned int mxcsr;
  30   __asm__ ("stmxcsr %0" : "=m" (mxcsr));
  31   /* Preserve SSE exception flags but restore other state in
  32      MXCSR.  */
  33   mxcsr &= FE_ALL_EXCEPT_X86;
  34   if (modep == FE_DFL_MODE)
  35     {
  36       cw = _FPU_DEFAULT;
  37       /* Default MXCSR state has all bits zero except for those
  38          masking exceptions.  */
  39       mxcsr |= FE_ALL_EXCEPT_X86 << 7;
  40     }
  41   else
  42     {
  43       cw = modep->__control_word;
  44       mxcsr |= modep->__mxcsr & ~FE_ALL_EXCEPT_X86;
  45     }
  46   _FPU_SETCW (cw);
  47   __asm__ ("ldmxcsr %0" : : "m" (mxcsr));
  48   return 0;
  49 }