gcc/ada/libgnat/s-fatgen.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . F A T _ G E N                        --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2017, 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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This generic package provides a target independent implementation of the
  33 --  floating-point attributes that denote functions. The implementations here
  34 --  are portable, but very slow. The runtime contains a set of instantiations
  35 --  of this package for all predefined floating-point types, and these should
  36 --  be replaced by efficient assembly language code where possible.
  37
  38 generic
  39     type T is digits <>;
  40
  41 package System.Fat_Gen is
  42    pragma Pure;
  43
  44    subtype UI is Integer;
  45    --  The runtime representation of universal integer for the purposes of
  46    --  this package is integer. The expander generates conversions for the
  47    --  actual type used. For functions returning universal integer, there
  48    --  is no problem, since the result always is in range of integer. For
  49    --  input arguments, the expander has to do some special casing to deal
  50    --  with the (very annoying) cases of out of range values. If we used
  51    --  Long_Long_Integer to represent universal, then there would be no
  52    --  problem, but the resulting inefficiency would be annoying.
  53
  54    function Adjacent          (X, Towards : T)              return T;
  55
  56    function Ceiling           (X : T)                       return T;
  57
  58    function Compose           (Fraction : T; Exponent : UI) return T;
  59
  60    function Copy_Sign         (Value, Sign : T)             return T;
  61
  62    function Exponent          (X : T)                       return UI;
  63
  64    function Floor             (X : T)                       return T;
  65
  66    function Fraction          (X : T)                       return T;
  67
  68    function Leading_Part      (X : T; Radix_Digits : UI)    return T;
  69
  70    function Machine           (X : T)                       return T;
  71
  72    function Machine_Rounding  (X : T)                       return T;
  73
  74    function Model             (X : T)                       return T;
  75
  76    function Pred              (X : T)                       return T;
  77
  78    function Remainder         (X, Y : T)                    return T;
  79
  80    function Rounding          (X : T)                       return T;
  81
  82    function Scaling           (X : T; Adjustment : UI)      return T;
  83
  84    function Succ              (X : T)                       return T;
  85
  86    function Truncation        (X : T)                       return T;
  87
  88    function Unbiased_Rounding (X : T)                       return T;
  89
  90    function Valid (X : not null access T) return Boolean;
  91    --  This function checks if the object of type T referenced by X is valid,
  92    --  and returns True/False accordingly. The parameter is passed by reference
  93    --  (access) here, as the object of type T may be an abnormal value that
  94    --  cannot be passed in a floating-point register, and the whole point of
  95    --  'Valid is to prevent exceptions. Note that the object of type T must
  96    --  have the natural alignment for type T.
  97
  98    type S is new String (1 .. T'Size / Character'Size);
  99    type P is access all S with Storage_Size => 0;
 100    --  Buffer and access types used to initialize temporaries for validity
 101    --  checks, if the value to be checked has reverse scalar storage order, or
 102    --  is not known to be properly aligned (for example it appears in a packed
 103    --  record). In this case, we cannot call Valid since Valid assumes proper
 104    --  full alignment. Instead, we copy the value to a temporary location using
 105    --  type S (we cannot simply do a copy of a T value, because the value might
 106    --  be invalid, in which case it might not be possible to copy it through a
 107    --  floating point register).
 108
 109 private
 110    pragma Inline (Machine);
 111    pragma Inline (Model);
 112
 113    --  Note: previously the validity checking subprograms (Unaligned_Valid and
 114    --  Valid) were also inlined, but this was changed since there were some
 115    --  problems with this inlining in optimized mode, and in any case it seems
 116    --  better to avoid this inlining (space and robustness considerations).
 117
 118 end System.Fat_Gen;