sysdeps/m68k/fpu_control.h

   1 /* 68k FPU control word definitions.
   2 Copyright (C) 1996 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   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., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #ifndef _FPU_CONTROL_H
  21 #define _FPU_CONTROL_H
  22
  23 /*
  24  * Motorola floating point control register bits.
  25  *
  26  * 31-16  -> reserved (read as 0, ignored on write)
  27  * 15     -> enable trap for BSUN exception
  28  * 14     -> enable trap for SNAN exception
  29  * 13     -> enable trap for OPERR exception
  30  * 12     -> enable trap for OVFL exception
  31  * 11     -> enable trap for UNFL exception
  32  * 10     -> enable trap for DZ exception
  33  *  9     -> enable trap for INEX2 exception
  34  *  8     -> enable trap for INEX1 exception
  35  *  7-6   -> Precision Control
  36  *  5-4   -> Rounding Control
  37  *  3-0   -> zero (read as 0, write as 0)
  38  *
  39  *
  40  * Precision Control:
  41  * 00 - round to extended precision
  42  * 01 - round to single precision
  43  * 10 - round to double precision
  44  * 11 - undefined
  45  *
  46  * Rounding Control:
  47  * 00 - rounding to nearest (RN)
  48  * 01 - rounding toward zero (RZ)
  49  * 10 - rounding (down)toward minus infinity (RM)
  50  * 11 - rounding (up) toward plus infinity (RP)
  51  *
  52  * The hardware default is 0x0000. I choose 0x5400.
  53  */
  54
  55 #include <features.h>
  56
  57 /* masking of interrupts */
  58 #define _FPU_MASK_BSUN  0x8000
  59 #define _FPU_MASK_SNAN  0x4000
  60 #define _FPU_MASK_OPERR 0x2000
  61 #define _FPU_MASK_OVFL  0x1000
  62 #define _FPU_MASK_UNFL  0x0800
  63 #define _FPU_MASK_DZ    0x0400
  64 #define _FPU_MASK_INEX1 0x0200
  65 #define _FPU_MASK_INEX2 0x0100
  66
  67 /* precision control */
  68 #define _FPU_EXTENDED 0x00   /* RECOMMENDED */
  69 #define _FPU_DOUBLE   0x80
  70 #define _FPU_SINGLE   0x40     /* DO NOT USE */
  71
  72 /* rounding control */
  73 #define _FPU_RC_NEAREST 0x00    /* RECOMMENDED */
  74 #define _FPU_RC_ZERO    0x10
  75 #define _FPU_RC_DOWN    0x20
  76 #define _FPU_RC_UP      0x30
  77
  78 #define _FPU_RESERVED 0xFFFF000F  /* Reserved bits in fpucr */
  79
  80
  81 /* Now two recommended fpucr */
  82
  83 /* The fdlibm code requires no interrupts for exceptions.  Don't
  84    change the rounding mode, it would break long double I/O!  */
  85 #define _FPU_DEFAULT  0x00000000
  86
  87 /* IEEE:  same as above, but exceptions.  We must make it non-zero so
  88    that __setfpucw works.  This bit will be ignored.  */
  89 #define _FPU_IEEE     0x00000001
  90
  91 /* Type of the control word.  */
  92 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__SI__)));
  93
  94 /* Macros for accessing the hardware control word.  */
  95 #define _FPU_GETCW(cw) __asm__ ("fmove%.l %!, %0" : "=dm" (cw))
  96 #define _FPU_SETCW(cw) __asm__ volatile ("fmove%.l %0, %!" : : "dm" (cw))
  97
  98 /* Default control word set at startup.  */
  99 extern fpu_control_t __fpu_control;
 100
 101 __BEGIN_DECLS
 102
 103 /* Called at startup.  It can be used to manipulate fpu control register.  */
 104 extern void __setfpucw __P ((fpu_control_t));
 105
 106 __END_DECLS
 107
 108 #endif /* _M68K_FPU_CONTROL_H */