1 /* Emulation for ldexpl.
2 Contributed by Paolo Bonzini
3
4 Copyright 2002-2003, 2007-2012 Free Software Foundation, Inc.
5
6 This file is part of gnulib.
7
8 This program is free software: you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
12
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20
21 #include <config.h>
22
23 /* Specification. */
24 #include <math.h>
25
26 #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
27
28 long double
ldexpl(long double x,int exp)29 ldexpl (long double x, int exp)
30 {
31 return ldexp (x, exp);
32 }
33
34 #else
35
36 # include <float.h>
37 # include "fpucw.h"
38
39 long double
ldexpl(long double x,int exp)40 ldexpl (long double x, int exp)
41 {
42 long double factor;
43 int bit;
44 DECL_LONG_DOUBLE_ROUNDING
45
46 BEGIN_LONG_DOUBLE_ROUNDING ();
47
48 /* Check for zero, nan and infinity. */
49 if (!(isnanl (x) || x + x == x))
50 {
51 if (exp < 0)
52 {
53 exp = -exp;
54 factor = 0.5L;
55 }
56 else
57 factor = 2.0L;
58
59 if (exp > 0)
60 for (bit = 1;;)
61 {
62 /* Invariant: Here bit = 2^i, factor = 2^-2^i or = 2^2^i,
63 and bit <= exp. */
64 if (exp & bit)
65 x *= factor;
66 bit <<= 1;
67 if (bit > exp)
68 break;
69 factor = factor * factor;
70 }
71 }
72
73 END_LONG_DOUBLE_ROUNDING ();
74
75 return x;
76 }
77
78 #endif
79
80 #if 0
81 int
82 main (void)
83 {
84 long double x;
85 int y;
86 for (y = 0; y < 29; y++)
87 printf ("%5d %.16Lg %.16Lg\n", y, ldexpl (0.8L, y), ldexpl (0.8L, -y) * ldexpl (0.8L, y));
88 }
89 #endif
90