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glibc  2.9
s_ilogbl.c
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00001 /* Software floating-point emulation.
00002    ilogbl(x, exp)
00003    Copyright (C) 1999 Free Software Foundation, Inc.
00004    This file is part of the GNU C Library.
00005    Contributed by Jakub Jelinek (jj@ultra.linux.cz).
00006 
00007    The GNU C Library is free software; you can redistribute it and/or
00008    modify it under the terms of the GNU Lesser General Public
00009    License as published by the Free Software Foundation; either
00010    version 2.1 of the License, or (at your option) any later version.
00011 
00012    The GNU C Library is distributed in the hope that it will be useful,
00013    but WITHOUT ANY WARRANTY; without even the implied warranty of
00014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015    Lesser General Public License for more details.
00016 
00017    You should have received a copy of the GNU Lesser General Public
00018    License along with the GNU C Library; if not, write to the Free
00019    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00020    02111-1307 USA.  */
00021 
00022 /* ilogbl(long double x)
00023  * return the binary exponent of non-zero x
00024  * ilogbl(0) = 0x80000001
00025  * ilogbl(inf/NaN) = 0x7fffffff (no signal is raised)
00026  */
00027 
00028 #include "soft-fp.h"
00029 #include "quad.h"
00030 #include <math.h>
00031 
00032 int __ilogbl(long double x)
00033 {
00034   FP_DECL_EX;
00035   FP_DECL_Q(X);
00036 
00037 /*
00038   FP_UNPACK_Q(X, x);
00039   switch (X_c)
00040     {
00041     case FP_CLS_ZERO:
00042       return FP_ILOGB0;
00043     case FP_CLS_NAN:
00044     case FP_CLS_INF:
00045       return FP_ILOGBNAN;
00046     default:
00047       return X_e;
00048     }
00049  */
00050   FP_UNPACK_RAW_Q(X, x);
00051   switch (X_e)
00052     {
00053     default:
00054       return X_e - _FP_EXPBIAS_Q;
00055     case 0:
00056 #if (2 * _FP_W_TYPE_SIZE) < _FP_FRACBITS_Q
00057       if (_FP_FRAC_ZEROP_4(X))
00058        return FP_ILOGB0;
00059       else
00060        {
00061          _FP_I_TYPE shift;
00062          _FP_FRAC_CLZ_4(shift, X);
00063          shift -= _FP_FRACXBITS_Q;
00064          return X_e - _FP_EXPBIAS_Q - 1 + shift;
00065        }
00066 #else
00067       if (_FP_FRAC_ZEROP_2(X))
00068        return FP_ILOGB0;
00069       else
00070        {
00071          _FP_I_TYPE shift;
00072          _FP_FRAC_CLZ_2(shift, X);
00073          shift -= _FP_FRACXBITS_Q;
00074          return X_e - _FP_EXPBIAS_Q - 1 + shift;
00075        }
00076 #endif
00077     case _FP_EXPBIAS_Q:
00078       return FP_ILOGBNAN;
00079     }
00080 }
00081 
00082 weak_alias (__ilogbl, ilogbl)