1 /* Test for signaling NaN.
2 Copyright (C) 2013-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
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.
9
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.
14
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 <https://www.gnu.org/licenses/>. */
18
19 #include <math.h>
20 #include <math_private.h>
21 #include <nan-high-order-bit.h>
22
23 int
__issignaling(double x)24 __issignaling (double x)
25 {
26 uint64_t xi;
27 EXTRACT_WORDS64 (xi, x);
28 #if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
29 /* We only have to care about the high-order bit of x's significand, because
30 having it set (sNaN) already makes the significand different from that
31 used to designate infinity. */
32 return (xi & UINT64_C (0x7ff8000000000000)) == UINT64_C (0x7ff8000000000000);
33 #else
34 /* To keep the following comparison simple, toggle the quiet/signaling bit,
35 so that it is set for sNaNs. This is inverse to IEEE 754-2008 (as well as
36 common practice for IEEE 754-1985). */
37 xi ^= UINT64_C (0x0008000000000000);
38 /* We have to compare for greater (instead of greater or equal), because x's
39 significand being all-zero designates infinity not NaN. */
40 return (xi & UINT64_C (0x7fffffffffffffff)) > UINT64_C (0x7ff8000000000000);
41 #endif
42 }
43 libm_hidden_def (__issignaling)
44