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
38generic
39    type T is digits <>;
40
41package 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
120private
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
129end System.Fat_Gen;
130