gcc/ada/eval_fat.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             E V A L _ F A T                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2018, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This package provides for compile-time evaluation of static calls to the
  27 --  floating-point attribute functions. It is the compile-time equivalent of
  28 --  the System.Fat_Gen runtime package. The coding is quite similar, as are
  29 --  the subprogram specs, except that the type is passed as an explicit
  30 --  first parameter (and used via ttypes, to obtain the necessary information
  31 --  about the characteristics of the type for computing the results.
  32
  33 with Types;  use Types;
  34 with Uintp;  use Uintp;
  35 with Urealp; use Urealp;
  36
  37 package Eval_Fat is
  38
  39    subtype UI is Uint;
  40    --  The compile time representation of universal integer
  41
  42    subtype T is Ureal;
  43    --  The compile time representation of floating-point values
  44
  45    subtype R is Entity_Id;
  46    --  The compile time representation of the floating-point root type
  47
  48    --  The following functions perform the operation implied by their name
  49    --  which corresponds to the name of the attribute which they compute.
  50    --  The arguments correspond to the attribute function arguments.
  51
  52    function Adjacent          (RT : R; X, Towards : T)              return T;
  53
  54    function Ceiling           (RT : R; X : T)                       return T;
  55
  56    function Compose           (RT : R; Fraction : T; Exponent : UI) return T;
  57
  58    function Copy_Sign         (RT : R; Value, Sign : T)             return T;
  59
  60    function Exponent          (RT : R; X : T)                       return UI;
  61
  62    function Floor             (RT : R; X : T)                       return T;
  63
  64    function Fraction          (RT : R; X : T)                       return T;
  65
  66    function Leading_Part      (RT : R; X : T; Radix_Digits : UI)    return T;
  67
  68    function Model             (RT : R; X : T)                       return T;
  69
  70    function Pred              (RT : R; X : T)                       return T;
  71
  72    function Remainder         (RT : R; X, Y : T)                    return T;
  73
  74    function Rounding          (RT : R; X : T)                       return T;
  75
  76    function Scaling           (RT : R; X : T; Adjustment : UI)      return T;
  77
  78    function Succ              (RT : R; X : T)                       return T;
  79
  80    function Truncation        (RT : R; X : T)                       return T;
  81
  82    function Unbiased_Rounding (RT : R; X : T)                       return T;
  83
  84    --  The following global declarations are used by the Machine attribute
  85
  86    type Rounding_Mode is (Floor, Ceiling, Round, Round_Even);
  87    for Rounding_Mode use (0, 1, 2, 3);
  88    --  Used to indicate rounding mode for Machine attribute
  89    --  Note that C code in gigi knows that Round_Even is 3
  90
  91    --  The Machine attribute is special, in that it takes an extra argument
  92    --  indicating the rounding mode, and also an argument Enode that is a
  93    --  node used to post warnings (e.g. if asked to convert a negative zero
  94    --  on a machine for which Signed_Zeros is False).
  95
  96    function Machine
  97      (RT    : R;
  98       X     : T;
  99       Mode  : Rounding_Mode;
 100       Enode : Node_Id) return T;
 101
 102    procedure Decompose_Int
 103      (RT       : R;
 104       X        : T;
 105       Fraction : out UI;
 106       Exponent : out UI;
 107       Mode     : Rounding_Mode);
 108    --  Decomposes a floating-point number into fraction and exponent parts.
 109    --  The Fraction value returned is an integer representing the value
 110    --  Fraction * Scale, where Scale is the value (Machine_Radix_Value (RT) **
 111    --  Machine_Mantissa_Value (RT)). The value is obtained by using biased
 112    --  rounding (halfway cases round away from zero), round to even, a floor
 113    --  operation or a ceiling operation depending on the setting of Mode (see
 114    --  corresponding descriptions in Urealp).
 115
 116 end Eval_Fat;