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-rw-r--r--math/e_exp2l.c44
1 files changed, 41 insertions, 3 deletions
diff --git a/math/e_exp2l.c b/math/e_exp2l.c
index e7e493933a..8904d3e4a0 100644
--- a/math/e_exp2l.c
+++ b/math/e_exp2l.c
@@ -1,11 +1,49 @@
+/* Compute 2^x.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ 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>
+#include <float.h>
long double
__ieee754_exp2l (long double x)
{
- /* This is a very stupid and inprecise implementation. It'll get
- replaced sometime (soon?). */
- return __ieee754_expl (M_LN2l * x);
+ if (__builtin_expect (isless (x, (long double) LDBL_MAX_EXP), 1))
+ {
+ if (__builtin_expect (isgreaterequal (x, (long double) (LDBL_MIN_EXP
+ - LDBL_MANT_DIG
+ - 1)), 1))
+ {
+ int intx = (int) x;
+ long double fractx = x - intx;
+ return __scalbnl (__ieee754_expl (M_LN2l * fractx), intx);
+ }
+ else
+ {
+ /* Underflow or exact zero. */
+ if (__isinfl (x))
+ return 0;
+ else
+ return LDBL_MIN * LDBL_MIN;
+ }
+ }
+ else
+ /* Infinity, NaN or overflow. */
+ return LDBL_MAX * x;
}
strong_alias (__ieee754_exp2l, __exp2l_finite)