• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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