Mercurial > hg > CbC > CbC_gcc
comparison libgfortran/generated/pow_i8_i4.c @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
parents | |
children | 84e7813d76e9 |
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68:561a7518be6b | 111:04ced10e8804 |
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1 /* Support routines for the intrinsic power (**) operator. | |
2 Copyright (C) 2004-2017 Free Software Foundation, Inc. | |
3 Contributed by Paul Brook | |
4 | |
5 This file is part of the GNU Fortran 95 runtime library (libgfortran). | |
6 | |
7 Libgfortran is free software; you can redistribute it and/or | |
8 modify it under the terms of the GNU General Public | |
9 License as published by the Free Software Foundation; either | |
10 version 3 of the License, or (at your option) any later version. | |
11 | |
12 Libgfortran is distributed in the hope that it will be useful, | |
13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 GNU General Public License for more details. | |
16 | |
17 Under Section 7 of GPL version 3, you are granted additional | |
18 permissions described in the GCC Runtime Library Exception, version | |
19 3.1, as published by the Free Software Foundation. | |
20 | |
21 You should have received a copy of the GNU General Public License and | |
22 a copy of the GCC Runtime Library Exception along with this program; | |
23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 <http://www.gnu.org/licenses/>. */ | |
25 | |
26 #include "libgfortran.h" | |
27 | |
28 | |
29 /* Use Binary Method to calculate the powi. This is not an optimal but | |
30 a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of | |
31 Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art | |
32 of Computer Programming", 3rd Edition, 1998. */ | |
33 | |
34 #if defined (HAVE_GFC_INTEGER_8) && defined (HAVE_GFC_INTEGER_4) | |
35 | |
36 GFC_INTEGER_8 pow_i8_i4 (GFC_INTEGER_8 a, GFC_INTEGER_4 b); | |
37 export_proto(pow_i8_i4); | |
38 | |
39 GFC_INTEGER_8 | |
40 pow_i8_i4 (GFC_INTEGER_8 a, GFC_INTEGER_4 b) | |
41 { | |
42 GFC_INTEGER_8 pow, x; | |
43 GFC_INTEGER_4 n; | |
44 GFC_UINTEGER_4 u; | |
45 | |
46 n = b; | |
47 x = a; | |
48 pow = 1; | |
49 if (n != 0) | |
50 { | |
51 if (n < 0) | |
52 { | |
53 if (x == 1) | |
54 return 1; | |
55 if (x == -1) | |
56 return (n & 1) ? -1 : 1; | |
57 return (x == 0) ? 1 / x : 0; | |
58 } | |
59 else | |
60 { | |
61 u = n; | |
62 } | |
63 for (;;) | |
64 { | |
65 if (u & 1) | |
66 pow *= x; | |
67 u >>= 1; | |
68 if (u) | |
69 x *= x; | |
70 else | |
71 break; | |
72 } | |
73 } | |
74 return pow; | |
75 } | |
76 | |
77 #endif |