usr/src/lib/libm/common/C/significand.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 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 /*
  26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29
  30 #pragma weak __significand = significand
  31
  32 #include "libm.h"
  33
  34 double
  35 significand(double x) {
  36         int ix = ((int *) &x)[HIWORD] & ~0x80000000;
  37
  38         /* weed out 0/+-Inf/NaN because C99 ilogb raises invalid on them */
  39         if ((ix | ((int *) &x)[LOWORD]) == 0 || ix >= 0x7ff00000)
  40 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
  41                 return ((ix & 0x80000) != 0 ? x : x + x);
  42                 /* assumes sparc-like QNaN */
  43 #else
  44                 return (x + x);
  45 #endif
  46         else
  47                 return (scalbn(x, -ilogb(x)));
  48 }