--- /dev/null
+/* 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