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1 | ------------------------------------------------------------------------------ |
2 | -- -- | |
3084fecd | 3 | -- GNAT RUN-TIME COMPONENTS -- |
cacbc350 | 4 | -- -- |
fbf5a39b | 5 | -- S Y S T E M . E X N _ L L F -- |
cacbc350 RK |
6 | -- -- |
7 | -- B o d y -- | |
8 | -- -- | |
4b490c1e | 9 | -- Copyright (C) 1992-2020, Free Software Foundation, Inc. -- |
cacbc350 RK |
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- -- | |
748086b7 | 13 | -- ware Foundation; either version 3, or (at your option) any later ver- -- |
cacbc350 RK |
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 -- | |
748086b7 JJ |
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/>. -- | |
cacbc350 RK |
26 | -- -- |
27 | -- GNAT was originally developed by the GNAT team at New York University. -- | |
71ff80dc | 28 | -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
cacbc350 RK |
29 | -- -- |
30 | ------------------------------------------------------------------------------ | |
31 | ||
596b25f9 AC |
32 | -- Note: the reason for treating exponents in the range 0 .. 4 specially is |
33 | -- to ensure identical results to the static inline expansion in the case of | |
34 | -- a compile time known exponent in this range. The use of Float'Machine and | |
35 | -- Long_Float'Machine is to avoid unwanted extra precision in the results. | |
36 | ||
00f45f30 AC |
37 | -- Note that for a negative exponent in Left ** Right, we compute the result |
38 | -- as: | |
39 | ||
40 | -- 1.0 / (Left ** (-Right)) | |
41 | ||
42 | -- Note that the case of Left being zero is not special, it will simply result | |
43 | -- in a division by zero at the end, yielding a correctly signed infinity, or | |
44 | -- possibly generating an overflow. | |
45 | ||
46 | -- Note on overflow: This coding assumes that the target generates infinities | |
47 | -- with standard IEEE semantics. If this is not the case, then the code | |
48 | -- for negative exponent may raise Constraint_Error. This follows the | |
49 | -- implementation permission given in RM 4.5.6(12). | |
50 | ||
fbf5a39b | 51 | package body System.Exn_LLF is |
cacbc350 | 52 | |
00f45f30 AC |
53 | subtype Negative is Integer range Integer'First .. -1; |
54 | ||
596b25f9 AC |
55 | function Exp |
56 | (Left : Long_Long_Float; | |
00f45f30 AC |
57 | Right : Natural) return Long_Long_Float; |
58 | -- Common routine used if Right is greater or equal to 5 | |
596b25f9 AC |
59 | |
60 | --------------- | |
61 | -- Exn_Float -- | |
62 | --------------- | |
63 | ||
64 | function Exn_Float | |
65 | (Left : Float; | |
66 | Right : Integer) return Float | |
67 | is | |
68 | Temp : Float; | |
69 | begin | |
70 | case Right is | |
71 | when 0 => | |
72 | return 1.0; | |
73 | when 1 => | |
74 | return Left; | |
75 | when 2 => | |
76 | return Float'Machine (Left * Left); | |
77 | when 3 => | |
78 | return Float'Machine (Left * Left * Left); | |
79 | when 4 => | |
80 | Temp := Float'Machine (Left * Left); | |
81 | return Float'Machine (Temp * Temp); | |
00f45f30 AC |
82 | when Negative => |
83 | return Float'Machine (1.0 / Exn_Float (Left, -Right)); | |
596b25f9 AC |
84 | when others => |
85 | return | |
86 | Float'Machine | |
87 | (Float (Exp (Long_Long_Float (Left), Right))); | |
88 | end case; | |
89 | end Exn_Float; | |
90 | ||
91 | -------------------- | |
92 | -- Exn_Long_Float -- | |
93 | -------------------- | |
94 | ||
95 | function Exn_Long_Float | |
96 | (Left : Long_Float; | |
97 | Right : Integer) return Long_Float | |
98 | is | |
99 | Temp : Long_Float; | |
100 | begin | |
101 | case Right is | |
102 | when 0 => | |
103 | return 1.0; | |
104 | when 1 => | |
105 | return Left; | |
106 | when 2 => | |
107 | return Long_Float'Machine (Left * Left); | |
108 | when 3 => | |
109 | return Long_Float'Machine (Left * Left * Left); | |
110 | when 4 => | |
111 | Temp := Long_Float'Machine (Left * Left); | |
112 | return Long_Float'Machine (Temp * Temp); | |
00f45f30 AC |
113 | when Negative => |
114 | return Long_Float'Machine (1.0 / Exn_Long_Float (Left, -Right)); | |
596b25f9 AC |
115 | when others => |
116 | return | |
117 | Long_Float'Machine | |
118 | (Long_Float (Exp (Long_Long_Float (Left), Right))); | |
119 | end case; | |
120 | end Exn_Long_Float; | |
121 | ||
fbf5a39b AC |
122 | ------------------------- |
123 | -- Exn_Long_Long_Float -- | |
124 | ------------------------- | |
cacbc350 | 125 | |
fbf5a39b AC |
126 | function Exn_Long_Long_Float |
127 | (Left : Long_Long_Float; | |
4bb43ffb | 128 | Right : Integer) return Long_Long_Float |
596b25f9 AC |
129 | is |
130 | Temp : Long_Long_Float; | |
131 | begin | |
132 | case Right is | |
133 | when 0 => | |
134 | return 1.0; | |
135 | when 1 => | |
136 | return Left; | |
137 | when 2 => | |
138 | return Left * Left; | |
139 | when 3 => | |
140 | return Left * Left * Left; | |
141 | when 4 => | |
142 | Temp := Left * Left; | |
143 | return Temp * Temp; | |
00f45f30 AC |
144 | when Negative => |
145 | return 1.0 / Exn_Long_Long_Float (Left, -Right); | |
596b25f9 AC |
146 | when others => |
147 | return Exp (Left, Right); | |
148 | end case; | |
149 | end Exn_Long_Long_Float; | |
150 | ||
151 | --------- | |
152 | -- Exp -- | |
153 | --------- | |
154 | ||
155 | function Exp | |
156 | (Left : Long_Long_Float; | |
00f45f30 | 157 | Right : Natural) return Long_Long_Float |
cacbc350 | 158 | is |
fbf5a39b AC |
159 | Result : Long_Long_Float := 1.0; |
160 | Factor : Long_Long_Float := Left; | |
00f45f30 | 161 | Exp : Natural := Right; |
cacbc350 RK |
162 | |
163 | begin | |
164 | -- We use the standard logarithmic approach, Exp gets shifted right | |
165 | -- testing successive low order bits and Factor is the value of the | |
aa635439 | 166 | -- base raised to the next power of 2. If the low order bit or Exp is |
00f45f30 AC |
167 | -- set, multiply the result by this factor. |
168 | ||
169 | loop | |
170 | if Exp rem 2 /= 0 then | |
171 | Result := Result * Factor; | |
172 | end if; | |
173 | ||
174 | Exp := Exp / 2; | |
175 | exit when Exp = 0; | |
176 | Factor := Factor * Factor; | |
177 | end loop; | |
178 | ||
179 | return Result; | |
596b25f9 | 180 | end Exp; |
cacbc350 | 181 | |
fbf5a39b | 182 | end System.Exn_LLF; |