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[glibc.git] / sysdeps / ieee754 / dbl-64 / s_issignaling.c
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1 /* Test for signaling NaN.
2 Copyright (C) 2013-2014 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
19 #include <math.h>
20 #include <math_private.h>
22 int
23 __issignaling (double x)
25 #ifdef HIGH_ORDER_BIT_IS_SET_FOR_SNAN
26 u_int32_t hxi;
27 GET_HIGH_WORD (hxi, x);
28 /* We only have to care about the high-order bit of x's significand, because
29 having it set (sNaN) already makes the significand different from that
30 used to designate infinity. */
31 return (hxi & 0x7ff80000) == 0x7ff80000;
32 #else
33 u_int32_t hxi, lxi;
34 EXTRACT_WORDS (hxi, lxi, x);
35 /* To keep the following comparison simple, toggle the quiet/signaling bit,
36 so that it is set for sNaNs. This is inverse to IEEE 754-2008 (as well as
37 common practice for IEEE 754-1985). */
38 hxi ^= 0x00080000;
39 /* If lxi != 0, then set any suitable bit of the significand in hxi. */
40 hxi |= (lxi | -lxi) >> 31;
41 /* We have to compare for greater (instead of greater or equal), because x's
42 significand being all-zero designates infinity not NaN. */
43 return (hxi & 0x7fffffff) > 0x7ff80000;
44 #endif
46 libm_hidden_def (__issignaling)