ports/sysdeps/alpha/fpu/bits/fenv.h

   1 /* Copyright (C) 1997-2014 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 =
  40 #define FE_DENORMAL     (1 << 22)
  41       FE_DENORMAL,
  42 #endif
  43
  44     FE_INEXACT =
  45 #define FE_INEXACT      (1 << 21)
  46       FE_INEXACT,
  47
  48     FE_UNDERFLOW =
  49 #define FE_UNDERFLOW    (1 << 20)
  50       FE_UNDERFLOW,
  51
  52     FE_OVERFLOW =
  53 #define FE_OVERFLOW     (1 << 19)
  54       FE_OVERFLOW,
  55
  56     FE_DIVBYZERO =
  57 #define FE_DIVBYZERO    (1 << 18)
  58       FE_DIVBYZERO,
  59
  60     FE_INVALID =
  61 #define FE_INVALID      (1 << 17)
  62       FE_INVALID,
  63
  64     FE_ALL_EXCEPT =
  65 #define FE_ALL_EXCEPT   (0x3f << 17)
  66       FE_ALL_EXCEPT
  67   };
  68
  69 /* Alpha chips support all four defined rouding modes.
  70
  71    Note that code must be compiled to use dynamic rounding (/d) instructions
  72    to see these changes.  For gcc this is -mfp-rounding-mode=d; for DEC cc
  73    this is -fprm d.  The default for both is static rounding to nearest.
  74
  75    These are shifted down 58 bits from the hardware fpcr because the
  76    functions are declared to take integers.  */
  77
  78 enum
  79   {
  80     FE_TOWARDZERO =
  81 #define FE_TOWARDZERO   0
  82       FE_TOWARDZERO,
  83
  84     FE_DOWNWARD =
  85 #define FE_DOWNWARD     1
  86       FE_DOWNWARD,
  87
  88     FE_TONEAREST =
  89 #define FE_TONEAREST    2
  90       FE_TONEAREST,
  91
  92     FE_UPWARD =
  93 #define FE_UPWARD       3
  94       FE_UPWARD,
  95   };
  96
  97 #ifdef __USE_GNU
  98 /* On later hardware, and later kernels for earlier hardware, we can forcibly
  99    underflow denormal inputs and outputs.  This can speed up certain programs
 100    significantly, usually without affecting accuracy.  */
 101 enum
 102   {
 103     FE_MAP_DMZ =        1UL << 12,      /* Map denorm inputs to zero */
 104 #define FE_MAP_DMZ      FE_MAP_DMZ
 105
 106     FE_MAP_UMZ =        1UL << 13,      /* Map underflowed outputs to zero */
 107 #define FE_MAP_UMZ      FE_MAP_UMZ
 108   };
 109 #endif
 110
 111 /* Type representing exception flags.  */
 112 typedef unsigned long int fexcept_t;
 113
 114 /* Type representing floating-point environment.  */
 115 typedef unsigned long int fenv_t;
 116
 117 /* If the default argument is used we use this value.  Note that due to
 118    architecture-specified page mappings, no user-space pointer will ever
 119    have its two high bits set.  Co-opt one.  */
 120 #define FE_DFL_ENV      ((const fenv_t *) 0x8800000000000000UL)
 121
 122 #ifdef __USE_GNU
 123 /* Floating-point environment where none of the exceptions are masked.  */
 124 # define FE_NOMASK_ENV  ((const fenv_t *) 0x880000000000003eUL)
 125
 126 /* Floating-point environment with (processor-dependent) non-IEEE floating
 127    point.  In this case, mapping denormals to zero.  */
 128 # define FE_NONIEEE_ENV ((const fenv_t *) 0x8800000000003000UL)
 129 #endif
 130
 131 /* The system calls to talk to the kernel's FP code.  */
 132 extern unsigned long int __ieee_get_fp_control (void) __THROW;
 133 extern void __ieee_set_fp_control (unsigned long int __value) __THROW;