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glibc  2.9
e_scalb.c
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00001 /* Copyright (C) 1997, 1999 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <math.h>
00021 #include "math_private.h"
00022 #include "mathimpl.h"
00023 
00024 #ifndef SUFF
00025 #define SUFF
00026 #endif
00027 #ifndef float_type
00028 #define float_type double
00029 #endif
00030 
00031 #define CONCATX(a,b) __CONCAT(a,b)
00032 #define s(name) CONCATX(name,SUFF)
00033 #define m81(func) __m81_u(s(func))
00034 
00035 float_type
00036 s(__ieee754_scalb) (float_type x, float_type fn)
00037 {
00038   float_type retval;
00039   unsigned long x_cond = __m81_test (x);
00040   unsigned long fn_cond = __m81_test (fn);
00041 
00042   if ((x_cond | fn_cond) & __M81_COND_NAN)
00043     return x * fn;
00044 
00045   if (fn_cond & __M81_COND_INF)
00046     {
00047       if (!(fn_cond & __M81_COND_NEG))
00048        return x * fn;
00049       else if (x_cond & __M81_COND_ZERO)
00050        return x;
00051       else
00052        return x / -fn;
00053     }
00054 
00055   if (m81(__rint) (fn) != fn)
00056     return (x - x) / (x - x);
00057 
00058   __asm ("fscale%.x %1, %0" : "=f" (retval) : "f" (fn), "0" (x));
00059   return retval;
00060 }