fpu_control.h 3.1 KB

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  1. /* FPU control word bits. x86-64 version.
  2. Copyright (C) 1993,1995,1996,1997,1998,2000,2001,2002 Free Software Foundation, Inc.
  3. This file is part of the GNU C Library.
  4. Contributed by Olaf Flebbe.
  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, write to the Free
  15. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  16. 02111-1307 USA. */
  17. #ifndef _FPU_CONTROL_H
  18. #define _FPU_CONTROL_H 1
  19. /* Note that this file sets on x86-64 only the x87 FPU, it does not
  20. touch the SSE unit. */
  21. /* Here is the dirty part. Set up your 387 through the control word
  22. * (cw) register.
  23. *
  24. * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0
  25. * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM
  26. *
  27. * IM: Invalid operation mask
  28. * DM: Denormalized operand mask
  29. * ZM: Zero-divide mask
  30. * OM: Overflow mask
  31. * UM: Underflow mask
  32. * PM: Precision (inexact result) mask
  33. *
  34. * Mask bit is 1 means no interrupt.
  35. *
  36. * PC: Precision control
  37. * 11 - round to extended precision
  38. * 10 - round to double precision
  39. * 00 - round to single precision
  40. *
  41. * RC: Rounding control
  42. * 00 - rounding to nearest
  43. * 01 - rounding down (toward - infinity)
  44. * 10 - rounding up (toward + infinity)
  45. * 11 - rounding toward zero
  46. *
  47. * IC: Infinity control
  48. * That is for 8087 and 80287 only.
  49. *
  50. * The hardware default is 0x037f which we use.
  51. */
  52. #include <features.h>
  53. /* masking of interrupts */
  54. #define _FPU_MASK_IM 0x01
  55. #define _FPU_MASK_DM 0x02
  56. #define _FPU_MASK_ZM 0x04
  57. #define _FPU_MASK_OM 0x08
  58. #define _FPU_MASK_UM 0x10
  59. #define _FPU_MASK_PM 0x20
  60. /* precision control */
  61. #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */
  62. #define _FPU_DOUBLE 0x200
  63. #define _FPU_SINGLE 0x0
  64. /* rounding control */
  65. #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */
  66. #define _FPU_RC_DOWN 0x400
  67. #define _FPU_RC_UP 0x800
  68. #define _FPU_RC_ZERO 0xC00
  69. #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
  70. /* The fdlibm code requires strict IEEE double precision arithmetic,
  71. and no interrupts for exceptions, rounding to nearest. */
  72. #define _FPU_DEFAULT 0x037f
  73. /* IEEE: same as above. */
  74. #define _FPU_IEEE 0x037f
  75. /* Type of the control word. */
  76. typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
  77. /* Macros for accessing the hardware control word. */
  78. #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
  79. #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
  80. /* Default control word set at startup. */
  81. extern fpu_control_t __fpu_control;
  82. #endif /* fpu_control.h */