usr/src/lib/libm/common/m9x/llround.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 __llround = llround
  31 #if defined(__sparcv9) || defined(__amd64)
  32 #pragma weak lround = llround
  33 #pragma weak __lround = llround
  34 #endif
  35
  36 /*
  37  * llround(x) rounds its argument to the nearest integer, rounding
  38  * ties away from zero, and converts the result to a 64 bit signed
  39  * integer.
  40  *
  41  * If x is NaN, infinite, or so large that the nearest integer
  42  * would exceed 64 bits, the invalid operation exception is raised.
  43  */
  44
  45 #include "libm.h"
  46
  47 long long
  48 llround(double x) {
  49         union {
  50                 unsigned i[2];
  51                 double d;
  52         } xx;
  53         unsigned hx, sx, i;
  54
  55         xx.d = x;
  56         hx = xx.i[HIWORD] & ~0x80000000;
  57         sx = xx.i[HIWORD] & 0x80000000;
  58
  59         if (hx < 0x43300000) { /* |x| < 2^52 */
  60                 /* handle |x| < 1 */
  61                 if (hx < 0x3ff00000) {
  62                         if (hx >= 0x3fe00000)
  63                                 return (sx ? -1LL : 1LL);
  64                         return (0LL);
  65                 }
  66
  67                 /* round x at the integer bit */
  68                 if (hx < 0x41300000) {
  69                         i = 1 << (0x412 - (hx >> 20));
  70                         xx.i[HIWORD] = (xx.i[HIWORD] + i) & ~(i | (i - 1));
  71                         xx.i[LOWORD] = 0;
  72                 } else {
  73                         i = 1 << (0x432 - (hx >> 20));
  74                         xx.i[LOWORD] += i;
  75                         if (xx.i[LOWORD] < i)
  76                                 xx.i[HIWORD]++;
  77                         xx.i[LOWORD] &= ~(i | (i - 1));
  78                 }
  79         }
  80
  81         /* now x is nan, inf, or integral */
  82         return ((long long) xx.d);
  83 }