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 __lround = lround
  31 
  32 /*
  33  * lround(x) rounds its argument to the nearest integer, rounding ties
  34  * away from zero, and converts the result to a 32 bit signed integer.
  35  *
  36  * If x is NaN, infinite, or so large that the nearest integer
  37  * would exceed 32 bits, the invalid operation exception is raised.
  38  */
  39 
  40 #include <sys/isa_defs.h> /* _ILP32 */
  41 #include "libm.h"
  42 
  43 #if defined(_ILP32)
  44 long
  45 lround(double x) {
  46         union {
  47                 unsigned i[2];
  48                 double d;
  49         } xx;
  50         unsigned hx, sx, i;
  51 
  52         xx.d = x;
  53         hx = xx.i[HIWORD] & ~0x80000000;
  54         sx = xx.i[HIWORD] & 0x80000000;
  55         if (hx < 0x43300000) {       /* |x| < 2^52 */
  56                 if (hx < 0x3ff00000) {       /* |x| < 1 */
  57                         if (hx >= 0x3fe00000)
  58                                 return (sx ? -1L : 1L);
  59                         return (0L);
  60                 }
  61 
  62                 /* round x at the integer bit */
  63                 if (hx < 0x41300000) {
  64                         i = 1 << (0x412 - (hx >> 20));
  65                         xx.i[HIWORD] = (xx.i[HIWORD] + i) & ~(i | (i - 1));
  66                         xx.i[LOWORD] = 0;
  67                 } else {
  68                         i = 1 << (0x432 - (hx >> 20));
  69                         xx.i[LOWORD] += i;
  70                         if (xx.i[LOWORD] < i)
  71                                 xx.i[HIWORD]++;
  72                         xx.i[LOWORD] &= ~(i | (i - 1));
  73                 }
  74         }
  75 
  76         /* now x is nan, inf, or integral */
  77         return ((long) xx.d);
  78 }
  79 #else
  80 #error Unsupported architecture
  81 #endif  /* defined(_ILP32) */