s_llrint.c 2.3 KB

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  1. /* Round argument to nearest integral value according to current rounding
  2. direction.
  3. Copyright (C) 1997, 2004, 2006 Free Software Foundation, Inc.
  4. This file is part of the GNU C Library.
  5. Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
  6. The GNU C Library is free software; you can redistribute it and/or
  7. modify it under the terms of the GNU Lesser General Public
  8. License as published by the Free Software Foundation; either
  9. version 2.1 of the License, or (at your option) any later version.
  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. 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. #include <features.h>
  18. /* Prevent math.h from defining a colliding inline */
  19. #undef __USE_EXTERN_INLINES
  20. #include <math.h>
  21. #include "math_private.h"
  22. static const double two52[2] =
  23. {
  24. 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  25. -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  26. };
  27. long long int
  28. llrint (double x)
  29. {
  30. int32_t _j0;
  31. u_int32_t i1, i0;
  32. long long int result;
  33. volatile double w;
  34. double t;
  35. int sx;
  36. EXTRACT_WORDS (i0, i1, x);
  37. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  38. sx = i0 >> 31;
  39. i0 &= 0xfffff;
  40. i0 |= 0x100000;
  41. if (_j0 < 20)
  42. {
  43. w = two52[sx] + x;
  44. t = w - two52[sx];
  45. EXTRACT_WORDS (i0, i1, t);
  46. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  47. i0 &= 0xfffff;
  48. i0 |= 0x100000;
  49. result = (_j0 < 0 ? 0 : i0 >> (20 - _j0));
  50. }
  51. else if (_j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  52. {
  53. if (_j0 >= 52)
  54. result = (((long long int) i0 << 32) | i1) << (_j0 - 52);
  55. else
  56. {
  57. w = two52[sx] + x;
  58. t = w - two52[sx];
  59. EXTRACT_WORDS (i0, i1, t);
  60. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  61. i0 &= 0xfffff;
  62. i0 |= 0x100000;
  63. if (_j0 == 20)
  64. result = (long long int) i0;
  65. else
  66. result = ((long long int) i0 << (_j0 - 20)) | (i1 >> (52 - _j0));
  67. }
  68. }
  69. else
  70. {
  71. /* The number is too large. It is left implementation defined
  72. what happens. */
  73. return (long long int) x;
  74. }
  75. return sx ? -result : result;
  76. }
  77. libm_hidden_def(llrint)