File : 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) 1992-2012, 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;