s_llrint.c 2.4 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, write to the Free
  16. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17. 02111-1307 USA. */
  18. #include <features.h>
  19. /* Prevent math.h from defining a colliding inline */
  20. #undef __USE_EXTERN_INLINES
  21. #include <math.h>
  22. #include "math_private.h"
  23. static const double two52[2] =
  24. {
  25. 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  26. -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  27. };
  28. long long int
  29. llrint (double x)
  30. {
  31. int32_t j0;
  32. u_int32_t i1, i0;
  33. long long int result;
  34. volatile double w;
  35. double t;
  36. int sx;
  37. EXTRACT_WORDS (i0, i1, x);
  38. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  39. sx = i0 >> 31;
  40. i0 &= 0xfffff;
  41. i0 |= 0x100000;
  42. if (j0 < 20)
  43. {
  44. w = two52[sx] + x;
  45. t = w - two52[sx];
  46. EXTRACT_WORDS (i0, i1, t);
  47. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  48. i0 &= 0xfffff;
  49. i0 |= 0x100000;
  50. result = (j0 < 0 ? 0 : i0 >> (20 - j0));
  51. }
  52. else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  53. {
  54. if (j0 >= 52)
  55. result = (((long long int) i0 << 32) | i1) << (j0 - 52);
  56. else
  57. {
  58. w = two52[sx] + x;
  59. t = w - two52[sx];
  60. EXTRACT_WORDS (i0, i1, t);
  61. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  62. i0 &= 0xfffff;
  63. i0 |= 0x100000;
  64. if (j0 == 20)
  65. result = (long long int) i0;
  66. else
  67. result = ((long long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  68. }
  69. }
  70. else
  71. {
  72. /* The number is too large. It is left implementation defined
  73. what happens. */
  74. return (long long int) x;
  75. }
  76. return sx ? -result : result;
  77. }
  78. libm_hidden_def(llrint)