sysdeps/alpha/fpu/bits/fenv.h

   1 /* Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   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
  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
  19 #ifndef _FENV_H
  20 # error "Never use <bits/fenv.h> directly; include <fenv.h> instead."
  21 #endif
  22
  23
  24 /* Define the bits representing the exception.
  25
  26    Note that these are the bit positions as defined by the OSF/1
  27    ieee_{get,set}_control_word interface and not by the hardware fpcr.
  28
  29    See the Alpha Architecture Handbook section 4.7.7.3 for details,
  30    but in summary, trap shadows mean the hardware register can acquire
  31    extra exception bits so for proper IEEE support the tracking has to
  32    be done in software -- in this case with kernel support.
  33
  34    As to why the system call interface isn't in the same format as
  35    the hardware register, only those crazy folks at DEC can tell you.  */
  36
  37 enum
  38   {
  39 #ifdef __USE_GNU
  40     FE_DENORMAL =       1UL << 22,
  41 #define FE_DENORMAL     FE_DENORMAL
  42 #endif
  43
  44     FE_INEXACT =        1UL << 21,
  45 #define FE_INEXACT      FE_INEXACT
  46
  47     FE_UNDERFLOW =      1UL << 20,
  48 #define FE_UNDERFLOW    FE_UNDERFLOW
  49
  50     FE_OVERFLOW =       1UL << 19,
  51 #define FE_OVERFLOW     FE_OVERFLOW
  52
  53     FE_DIVBYZERO =      1UL << 18,
  54 #define FE_DIVBYZERO    FE_DIVBYZERO
  55
  56     FE_INVALID =        1UL << 17,
  57 #define FE_INVALID      FE_INVALID
  58
  59     FE_ALL_EXCEPT =     0x3f << 17
  60 #define FE_ALL_EXCEPT   FE_ALL_EXCEPT
  61   };
  62
  63 /* Alpha chips support all four defined rouding modes.
  64
  65    Note that code must be compiled to use dynamic rounding (/d) instructions
  66    to see these changes.  For gcc this is -mfp-rounding-mode=d; for DEC cc
  67    this is -fprm d.  The default for both is static rounding to nearest.
  68
  69    These are shifted down 58 bits from the hardware fpcr because the
  70    functions are declared to take integers.  */
  71
  72 enum
  73   {
  74     FE_TOWARDZERO =     0,
  75 #define FE_TOWARDZERO   FE_TOWARDZERO
  76
  77     FE_DOWNWARD =       1,
  78 #define FE_DOWNWARD     FE_DOWNWARD
  79
  80     FE_TONEAREST =      2,
  81 #define FE_TONEAREST    FE_TONEAREST
  82
  83     FE_UPWARD =         3,
  84 #define FE_UPWARD       FE_UPWARD
  85   };
  86
  87 #ifdef __USE_GNU
  88 /* On later hardware, and later kernels for earlier hardware, we can forcibly
  89    underflow denormal inputs and outputs.  This can speed up certain programs
  90    significantly, usually without affecting accuracy.  */
  91 enum
  92   {
  93     FE_MAP_DMZ =        1UL << 12,      /* Map denorm inputs to zero */
  94 #define FE_MAP_DMZ      FE_MAP_DMZ
  95
  96     FE_MAP_UMZ =        1UL << 13,      /* Map underflowed outputs to zero */
  97 #define FE_MAP_UMZ      FE_MAP_UMZ
  98   };
  99 #endif
 100
 101 /* Type representing exception flags.  */
 102 typedef unsigned long int fexcept_t;
 103
 104 /* Type representing floating-point environment.  */
 105 typedef unsigned long int fenv_t;
 106
 107 /* If the default argument is used we use this value.  Note that due to
 108    architecture-specified page mappings, no user-space pointer will ever
 109    have its two high bits set.  Co-opt one.  */
 110 #define FE_DFL_ENV      ((__const fenv_t *) 0x8800000000000000UL)
 111
 112 #ifdef __USE_GNU
 113 /* Floating-point environment where none of the exceptions are masked.  */
 114 # define FE_NOMASK_ENV  ((__const fenv_t *) 0x880000000000003eUL)
 115
 116 /* Floating-point environment with (processor-dependent) non-IEEE floating
 117    point.  In this case, mapping denormals to zero.  */
 118 # define FE_NONIEEE_ENV ((__const fenv_t *) 0x8800000000003000UL)
 119 #endif
 120
 121 /* The system calls to talk to the kernel's FP code.  */
 122 extern unsigned long int __ieee_get_fp_control (void) __THROW;
 123 extern void __ieee_set_fp_control (unsigned long int __value) __THROW;