--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libquadmath/math/issignalingq.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,43 @@
+/* Test for signaling NaN.
+   Copyright (C) 2013-2018 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 "quadmath-imp.h"
+
+int
+issignalingq (__float128 x)
+{
+  uint64_t hxi, lxi __attribute__ ((unused));
+  GET_FLT128_WORDS64 (hxi, lxi, x);
+#if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
+  /* We only have to care about the high-order bit of x's significand, because
+     having it set (sNaN) already makes the significand different from that
+     used to designate infinity.  */
+  return ((hxi & UINT64_C (0x7fff800000000000))
+          == UINT64_C (0x7fff800000000000));
+#else
+  /* To keep the following comparison simple, toggle the quiet/signaling bit,
+     so that it is set for sNaNs.  This is inverse to IEEE 754-2008 (as well as
+     common practice for IEEE 754-1985).  */
+  hxi ^= UINT64_C (0x0000800000000000);
+  /* If lxi != 0, then set any suitable bit of the significand in hxi.  */
+  hxi |= (lxi | -lxi) >> 63;
+  /* We have to compare for greater (instead of greater or equal), because x's
+     significand being all-zero designates infinity not NaN.  */
+  return (hxi & UINT64_C (0x7fffffffffffffff)) > UINT64_C (0x7fff800000000000);
+#endif
+}