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 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __rint = rint
  32 
  33 /*
  34  * rint(x) return x rounded to integral according to the rounding direction
  35  * rint(x) returns result with the same sign as x's,  including 0.0.
  36  */
  37 
  38 #include "libm.h"
  39 
  40 #if defined(__i386) && !defined(__amd64) && (!defined(__FLT_EVAL_METHOD__) || \
  41         __FLT_EVAL_METHOD__ != 0)
  42 
  43 extern enum fp_precision_type __swapRP(enum fp_precision_type);
  44 
  45 #define DECLRP(x)               enum fp_precision_type x;
  46 #define SWAPRP(new, x)          x = __swapRP(new);
  47 #define RESTRP(x)               (void) __swapRP(x);
  48 #else
  49 #define DECLRP(x)
  50 #define SWAPRP(new, x)
  51 #define RESTRP(x)
  52 #endif
  53 
  54 static const double two52 = 4503599627370496.0, zero = 0.0, one = 1.0;
  55 
  56 double
  57 rint(double x)
  58 {
  59         DECLRP(rp)
  60         double t, w;
  61         int ix, hx;
  62 
  63         ix = ((int *)&x)[HIWORD];
  64         hx = ix & ~0x80000000;
  65 
  66         if (hx >= 0x43300000)
  67                 return (x * one);
  68 
  69         t = (ix < 0) ? -two52 : two52;
  70         SWAPRP(fp_double, rp)           /* set precision mode to double */
  71         w = x + t;                      /* x+sign(x)*2**52 rounded */
  72         RESTRP(rp)                      /* restore precision mode */
  73 
  74         if (w == t)
  75                 return ((ix < 0) ? -zero : zero);
  76 
  77         return (w - t);
  78 }