gcc/ada/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) 1992-2013, 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
  92    --  is valid, and returns True/False accordingly. The parameter is
  93    --  passed by reference (access) here, as the object of type T may
  94    --  be an abnormal value that cannot be passed in a floating-point
  95    --  register, and the whole point of 'Valid is to prevent exceptions.
  96    --  Note that the object of type T must have the natural alignment
  97    --  for type T. See Unaligned_Valid for further discussion.
  98    --
  99    --  Note: this routine does not work for Vax_Float ???
 100
 101    function Unaligned_Valid (A : System.Address) return Boolean;
 102    --  This version of Valid is used if the floating-point value to
 103    --  be checked is not known to be aligned (for example it appears
 104    --  in a packed record). In this case, we cannot call Valid since
 105    --  Valid assumes proper full alignment. Instead Unaligned_Valid
 106    --  performs the same processing for a possibly unaligned float,
 107    --  by first doing a copy and then calling Valid. One might think
 108    --  that the front end could simply do a copy to an aligned temp,
 109    --  but remember that we may have an abnormal value that cannot
 110    --  be copied into a floating-point register, so things are a bit
 111    --  trickier than one might expect.
 112    --
 113    --  Note: Unaligned_Valid is never called for a target which does
 114    --  not require strict alignment (e.g. the ia32/x86), since on a
 115    --  target not requiring strict alignment, it is fine to pass a
 116    --  non-aligned value to the standard Valid routine.
 117    --
 118    --  Note: this routine does not work for Vax_Float ???
 119
 120 private
 121    pragma Inline (Machine);
 122    pragma Inline (Model);
 123
 124    --  Note: previously the validity checking subprograms (Unaligned_Valid and
 125    --  Valid) were also inlined, but this was changed since there were some
 126    --  problems with this inlining in optimized mode, and in any case it seems
 127    --  better to avoid this inlining (space and robustness considerations).
 128
 129 end System.Fat_Gen;