sysdeps/alpha/fpu/bits/fenv.h

   1 /* Copyright (C) 1997-2012 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _FENV_H
  19 # error "Never use <bits/fenv.h> directly; include <fenv.h> instead."
  20 #endif
  21
  22
  23 /* Define the bits representing the exception.
  24
  25    Note that these are the bit positions as defined by the OSF/1
  26    ieee_{get,set}_control_word interface and not by the hardware fpcr.
  27
  28    See the Alpha Architecture Handbook section 4.7.7.3 for details,
  29    but in summary, trap shadows mean the hardware register can acquire
  30    extra exception bits so for proper IEEE support the tracking has to
  31    be done in software -- in this case with kernel support.
  32
  33    As to why the system call interface isn't in the same format as
  34    the hardware register, only those crazy folks at DEC can tell you.  */
  35
  36 enum
  37   {
  38 #ifdef __USE_GNU
  39     FE_DENORMAL =       1UL << 22,
  40 #define FE_DENORMAL     FE_DENORMAL
  41 #endif
  42
  43     FE_INEXACT =        1UL << 21,
  44 #define FE_INEXACT      FE_INEXACT
  45
  46     FE_UNDERFLOW =      1UL << 20,
  47 #define FE_UNDERFLOW    FE_UNDERFLOW
  48
  49     FE_OVERFLOW =       1UL << 19,
  50 #define FE_OVERFLOW     FE_OVERFLOW
  51
  52     FE_DIVBYZERO =      1UL << 18,
  53 #define FE_DIVBYZERO    FE_DIVBYZERO
  54
  55     FE_INVALID =        1UL << 17,
  56 #define FE_INVALID      FE_INVALID
  57
  58     FE_ALL_EXCEPT =     0x3f << 17
  59 #define FE_ALL_EXCEPT   FE_ALL_EXCEPT
  60   };
  61
  62 /* Alpha chips support all four defined rouding modes.
  63
  64    Note that code must be compiled to use dynamic rounding (/d) instructions
  65    to see these changes.  For gcc this is -mfp-rounding-mode=d; for DEC cc
  66    this is -fprm d.  The default for both is static rounding to nearest.
  67
  68    These are shifted down 58 bits from the hardware fpcr because the
  69    functions are declared to take integers.  */
  70
  71 enum
  72   {
  73     FE_TOWARDZERO =     0,
  74 #define FE_TOWARDZERO   FE_TOWARDZERO
  75
  76     FE_DOWNWARD =       1,
  77 #define FE_DOWNWARD     FE_DOWNWARD
  78
  79     FE_TONEAREST =      2,
  80 #define FE_TONEAREST    FE_TONEAREST
  81
  82     FE_UPWARD =         3,
  83 #define FE_UPWARD       FE_UPWARD
  84   };
  85
  86 #ifdef __USE_GNU
  87 /* On later hardware, and later kernels for earlier hardware, we can forcibly
  88    underflow denormal inputs and outputs.  This can speed up certain programs
  89    significantly, usually without affecting accuracy.  */
  90 enum
  91   {
  92     FE_MAP_DMZ =        1UL << 12,      /* Map denorm inputs to zero */
  93 #define FE_MAP_DMZ      FE_MAP_DMZ
  94
  95     FE_MAP_UMZ =        1UL << 13,      /* Map underflowed outputs to zero */
  96 #define FE_MAP_UMZ      FE_MAP_UMZ
  97   };
  98 #endif
  99
 100 /* Type representing exception flags.  */
 101 typedef unsigned long int fexcept_t;
 102
 103 /* Type representing floating-point environment.  */
 104 typedef unsigned long int fenv_t;
 105
 106 /* If the default argument is used we use this value.  Note that due to
 107    architecture-specified page mappings, no user-space pointer will ever
 108    have its two high bits set.  Co-opt one.  */
 109 #define FE_DFL_ENV      ((const fenv_t *) 0x8800000000000000UL)
 110
 111 #ifdef __USE_GNU
 112 /* Floating-point environment where none of the exceptions are masked.  */
 113 # define FE_NOMASK_ENV  ((const fenv_t *) 0x880000000000003eUL)
 114
 115 /* Floating-point environment with (processor-dependent) non-IEEE floating
 116    point.  In this case, mapping denormals to zero.  */
 117 # define FE_NONIEEE_ENV ((const fenv_t *) 0x8800000000003000UL)
 118 #endif
 119
 120 /* The system calls to talk to the kernel's FP code.  */
 121 extern unsigned long int __ieee_get_fp_control (void) __THROW;
 122 extern void __ieee_set_fp_control (unsigned long int __value) __THROW;