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Optimize logb code for 64-bit machines

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Ulrich Drepper 2011-09-12 16:21:24 -04:00
parent 037e9fe21c
commit 8682f8b0e4
2 changed files with 48 additions and 0 deletions
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ChangeLog
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2011-09-12 Ulrich Drepper <drepper@gmail.com>
* sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c: New file.
2011-09-12 Andreas Schwab <schwab@redhat.com>
* sysdeps/unix/sysv/linux/bits/socket.h (__cmsg_nxthdr): Cast to

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sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c Normal file
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/* Compute radix independent exponent.
Copyright (C) 2011 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <math.h>
#include "math_private.h"
double
__logb (double x)
{
int64_t ix;
EXTRACT_WORDS64 (ix, x);
ix &= UINT64_C(0x7fffffffffffffff);
if (ix == 0)
return -1.0 / fabs (x);
unsigned int ex = ix >> 52;
if (ex == 0x7ff)
return x * x;
return ex == 0 ? -1022.0 : (double) (ex - 1023);
}
weak_alias (__logb, logb)
#ifdef NO_LONG_DOUBLE
strong_alias (__logb, __logbl)
weak_alias (__logb, logbl)
#endif