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  1. /*
  2.  * Copyright (C) 2007-2015 Free Software Foundation, Inc.
  3.  *
  4.  * This file is free software; you can redistribute it and/or modify it
  5.  * under the terms of the GNU General Public License as published by the
  6.  * Free Software Foundation; either version 3, or (at your option) any
  7.  * later version.
  8.  *
  9.  * This file is distributed in the hope that it will be useful, but
  10.  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12.  * General Public License for more details.
  13.  *
  14.  * Under Section 7 of GPL version 3, you are granted additional
  15.  * permissions described in the GCC Runtime Library Exception, version
  16.  * 3.1, as published by the Free Software Foundation.
  17.  *
  18.  * You should have received a copy of the GNU General Public License and
  19.  * a copy of the GCC Runtime Library Exception along with this program;
  20.  * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  21.  * <http://www.gnu.org/licenses/>.
  22.  */
  23.  
  24. #ifndef _SOFT_FLOAT
  25. #if __PREC == 32
  26.  #define X87CW          (0 << 8)        /* Single precision (24 bits) */
  27. #elif __PREC == 64
  28.  #define X87CW          (2 << 8)        /* Double precision (53 bits) */
  29. #elif __PREC == 80
  30.  #define X87CW          (3 << 8)        /* Extended precision (64 bits) */
  31. #else
  32.  #error "Wrong precision requested."
  33. #endif
  34.  
  35. #define X87CW_PCMASK    (3 << 8)
  36.  
  37. static void __attribute__((constructor))
  38. set_precision (void)
  39. {
  40.   unsigned short int cwd;
  41.  
  42.   asm volatile ("fstcw\t%0" : "=m" (cwd));
  43.  
  44.   cwd &= ~X87CW_PCMASK;
  45.   cwd |= X87CW;
  46.  
  47.   asm volatile ("fldcw\t%0" : : "m" (cwd));
  48. }
  49. #endif
  50.