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-rw-r--r--libm/w_log2.c46
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diff --git a/libm/w_log2.c b/libm/w_log2.c
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+/* Copyright (C) 2011-2016 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, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <math.h>
+#include "math_private.h"
+#if __UCLIBC_HAS_FENV__
+#include <fenv.h>
+#endif
+
+/* wrapper log2(x) */
+double
+log2 (double x)
+{
+#if __UCLIBC_HAS_FENV__
+ if (__builtin_expect (islessequal (x, 0.0), 0) && _LIB_VERSION != _IEEE_)
+ {
+ if (x == 0.0)
+ {
+ feraiseexcept (FE_DIVBYZERO);
+ return __kernel_standard (x, x, 48); /* log2(0) */
+ }
+ else
+ {
+ feraiseexcept (FE_INVALID);
+ return __kernel_standard (x, x, 49); /* log2(x<0) */
+ }
+ }
+#endif /* __UCLIBC_HAS_FENV__ */
+ return __ieee754_log2 (x);
+}
+libm_hidden_def(log2)