fesetround.c 1.5 KB

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  1. /* Set current rounding direction.
  2. Copyright (C) 1997, 2003, 2004, 2005 Free Software Foundation, Inc.
  3. This file is part of the GNU C Library.
  4. Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
  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. 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. You should have received a copy of the GNU Lesser General Public
  14. License along with the GNU C Library; if not, see
  15. <http://www.gnu.org/licenses/>. */
  16. #include <fenv.h>
  17. #include <unistd.h>
  18. int
  19. fesetround (int round)
  20. {
  21. unsigned short int cw;
  22. if ((round & ~0xc00) != 0)
  23. /* ROUND is no valid rounding mode. */
  24. return 1;
  25. __asm__ ("fnstcw %0" : "=m" (*&cw));
  26. cw &= ~0xc00;
  27. cw |= round;
  28. __asm__ ("fldcw %0" : : "m" (*&cw));
  29. #if 0
  30. /* If the CPU supports SSE we set the MXCSR as well. */
  31. if ((GLRO(dl_hwcap) & HWCAP_I386_XMM) != 0)
  32. {
  33. unsigned int xcw;
  34. __asm__ ("stmxcsr %0" : "=m" (*&xcw));
  35. xcw &= ~0x6000;
  36. xcw |= round << 3;
  37. __asm__ ("ldmxcsr %0" : : "m" (*&xcw));
  38. }
  39. #endif
  40. return 0;
  41. }