w_log2f.c 1.3 KB

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  1. /* Copyright (C) 2011-2016 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
  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. The GNU C Library is distributed in the hope that it will be useful,
  9. but WITHOUT ANY WARRANTY; without even the implied warranty of
  10. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11. Lesser General Public License for more details.
  12. You should have received a copy of the GNU Lesser General Public
  13. License along with the GNU C Library; if not, see
  14. <http://www.gnu.org/licenses/>. */
  15. #include <math.h>
  16. #include "math_private.h"
  17. #if __UCLIBC_HAS_FENV__
  18. #include <fenv.h>
  19. #endif
  20. /* wrapper log2f(x) */
  21. float
  22. log2f (float x)
  23. {
  24. #if __UCLIBC_HAS_FENV__
  25. if (__builtin_expect (islessequal (x, 0.0f), 0) && _LIB_VERSION != _IEEE_)
  26. {
  27. if (x == 0.0)
  28. {
  29. feraiseexcept (FE_DIVBYZERO);
  30. return __kernel_standard_f (x, x, 148); /* log2(0) */
  31. }
  32. else
  33. {
  34. feraiseexcept (FE_INVALID);
  35. return __kernel_standard_f (x, x, 149); /* log2(x<0) */
  36. }
  37. }
  38. #endif
  39. return (float) __ieee754_log2 ((double) x);
  40. }