sysdeps/x86_64/fpu_control.h

   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
   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
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #ifndef _FPU_CONTROL_H
  22 #define _FPU_CONTROL_H  1
  23
  24 /* Note that this file sets on x86-64 only the x87 FPU, it does not
  25    touch the SSE unit.  */
  26
  27 /* Here is the dirty part. Set up your 387 through the control word
  28  * (cw) register.
  29  *
  30  *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
  31  * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
  32  *
  33  * IM: Invalid operation mask
  34  * DM: Denormalized operand mask
  35  * ZM: Zero-divide mask
  36  * OM: Overflow mask
  37  * UM: Underflow mask
  38  * PM: Precision (inexact result) mask
  39  *
  40  * Mask bit is 1 means no interrupt.
  41  *
  42  * PC: Precision control
  43  * 11 - round to extended precision
  44  * 10 - round to double precision
  45  * 00 - round to single precision
  46  *
  47  * RC: Rounding control
  48  * 00 - rounding to nearest
  49  * 01 - rounding down (toward - infinity)
  50  * 10 - rounding up (toward + infinity)
  51  * 11 - rounding toward zero
  52  *
  53  * IC: Infinity control
  54  * That is for 8087 and 80287 only.
  55  *
  56  * The hardware default is 0x037f which we use.
  57  */
  58
  59 #include <features.h>
  60
  61 /* masking of interrupts */
  62 #define _FPU_MASK_IM  0x01
  63 #define _FPU_MASK_DM  0x02
  64 #define _FPU_MASK_ZM  0x04
  65 #define _FPU_MASK_OM  0x08
  66 #define _FPU_MASK_UM  0x10
  67 #define _FPU_MASK_PM  0x20
  68
  69 /* precision control */
  70 #define _FPU_EXTENDED 0x300     /* libm requires double extended precision.  */
  71 #define _FPU_DOUBLE   0x200
  72 #define _FPU_SINGLE   0x0
  73
  74 /* rounding control */
  75 #define _FPU_RC_NEAREST 0x0    /* RECOMMENDED */
  76 #define _FPU_RC_DOWN    0x400
  77 #define _FPU_RC_UP      0x800
  78 #define _FPU_RC_ZERO    0xC00
  79
  80 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
  81
  82
  83 /* The fdlibm code requires strict IEEE double precision arithmetic,
  84    and no interrupts for exceptions, rounding to nearest.  */
  85
  86 #define _FPU_DEFAULT  0x037f
  87
  88 /* IEEE:  same as above.  */
  89 #define _FPU_IEEE     0x037f
  90
  91 /* Type of the control word.  */
  92 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
  93
  94 /* Macros for accessing the hardware control word.  */
  95 #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
  96 #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
  97
  98 /* Default control word set at startup.  */
  99 extern fpu_control_t __fpu_control;
 100
 101 #endif  /* fpu_control.h */