usr/src/lib/libm/common/m9x/trunc.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 __trunc = trunc
  31
  32 #include "libm.h"
  33
  34 double
  35 trunc(double x) {
  36         union {
  37                 unsigned i[2];
  38                 double d;
  39         } xx;
  40         unsigned hx, sx, i;
  41
  42         xx.d = x;
  43         hx = xx.i[HIWORD] & ~0x80000000;
  44         sx = xx.i[HIWORD] & 0x80000000;
  45         if (hx < 0x43300000) {  /* |x| < 2^52 */
  46                 if (hx < 0x3ff00000)    /* |x| < 1 */
  47                         return (sx ? -0.0 : 0.0);
  48
  49                 /* chop x at the integer bit */
  50                 if (hx < 0x41300000) {
  51                         i = 1 << (0x412 - (hx >> 20));
  52                         xx.i[HIWORD] &= ~(i | (i - 1));
  53                         xx.i[LOWORD] = 0;
  54                 } else {
  55                         i = 1 << (0x432 - (hx >> 20));
  56                         xx.i[LOWORD] &= ~(i | (i - 1));
  57                 }
  58                 return (xx.d);
  59         } else if (hx < 0x7ff00000)
  60                 return (x);
  61         else
  62 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
  63                 return (hx >= 0x7ff80000 ? x : x + x);
  64                 /* assumes sparc-like QNaN */
  65 #else
  66                 return (x + x);
  67 #endif
  68 }