usr/src/lib/libm/common/C/isnan.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  23  */
  24 /*
  25  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28
  29 #pragma weak isnan = __isnan
  30 #pragma weak _isnan = __isnan
  31 #pragma weak _isnand = __isnan
  32 #pragma weak isnand = __isnan
  33
  34 #include "libm.h"
  35
  36 /*
  37  * The following implementation assumes fast 64-bit integer arith-
  38  * metic.  This is fine for sparc because we build libm in v8plus
  39  * mode.  It's also fine for sparcv9 and amd64.  For x86, it would
  40  * be better to use 32-bit code, but we have assembly for x86.
  41  */
  42 int
  43 __isnan(double x) {
  44         long long       llx;
  45
  46         llx = *(long long *)&x & ~0x8000000000000000ull;
  47         return ((unsigned long long)(0x7ff0000000000000ll - llx) >> 63);
  48 }