sysdeps/unix/sysv/linux/i386/fpu_control.h

   1 /* Copyright (C) 1993 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3 Contributed by Olaf Flebbe.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  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 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef _FPU_CONTROL_H
  21 #define _FPU_CONTROL_H
  22
  23 /* Here is the dirty part. Settup up your 387 through the control word
  24  * (cw) register.
  25  *
  26  *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
  27  * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
  28  *
  29  * IM: Invalid operation mask
  30  * DM: Denormalized operand mask
  31  * ZM: Zero-divide mask
  32  * OM: Overflow mask
  33  * UM: Underflow mask
  34  * PM: Precision (inexact result) mask
  35  *
  36  * Mask bit is 1 means no interrupt.
  37  *
  38  * PC: Precision control
  39  * 11 - round to extended precision
  40  * 10 - round to double precision
  41  * 00 - round to single precision
  42  *
  43  * RC: Rounding control
  44  * 00 - rounding to nearest
  45  * 01 - rounding down (toward - infinity)
  46  * 10 - rounding up (toward + infinity)
  47  * 11 - rounding toward zero
  48  *
  49  * IC: Infinity control
  50  * That is for 8087 and 80287 only.
  51  *
  52  * The hardware default is 0x037f. I choose 0x1372.
  53  */
  54
  55 #include <features.h>
  56
  57 /* masking of interrupts */
  58 #define _FPU_MASK_IM  0x01
  59 #define _FPU_MASK_DM  0x02
  60 #define _FPU_MASK_ZM  0x04
  61 #define _FPU_MASK_OM  0x08
  62 #define _FPU_MASK_UM  0x10
  63 #define _FPU_MASK_PM  0x20
  64
  65 /* precision control */
  66 #define _FPU_EXTENDED 0x300   /* RECOMMENDED */
  67 #define _FPU_DOUBLE   0x200
  68 #define _FPU_SINGLE   0x0     /* DO NOT USE */
  69
  70 /* rounding control */
  71 #define _FPU_RC_NEAREST 0x0    /* RECOMMENDED */
  72 #define _FPU_RC_DOWN    0x400
  73 #define _FPU_RC_UP      0x800
  74 #define _FPU_RC_ZERO    0xC00
  75
  76 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
  77
  78
  79 /* Now two recommended cw */
  80
  81 /* Linux default:
  82      - extended precision
  83      - rounding to nearest
  84      - exceptions on overflow, zero divide and NaN */
  85 #define _FPU_DEFAULT  0x1372
  86
  87 /* IEEE:  same as above, but exceptions */
  88 #define _FPU_IEEE     0x137f
  89
  90 /* private namespace. It should only be used in init-first.o. */
  91 extern unsigned short __fpu_control;
  92
  93 __BEGIN_DECLS
  94
  95 /* called in init-first.o. It can be used to manipulate 387 control word. */
  96 extern void __setfpucw __P ((unsigned short));
  97
  98 __END_DECLS
  99
 100 #endif  /* fpu_control.h */