File : 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) 1992-2014, 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 -- --
19 -- --
20 -- --
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;