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