usr/src/lib/libm/common/m9x/lrint.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 __lrint = lrint
  31
  32 /*
  33  * lrint(x) rounds its argument to the nearest integer according
  34  * to the current rounding direction and converts the result to
  35  * a 32 bit signed integer.
  36  *
  37  * If x is NaN, infinite, or so large that the nearest integer
  38  * would exceed 32 bits, the invalid operation exception is raised.
  39  * If x is not an integer, the inexact exception is raised.
  40  */
  41
  42 #include <sys/isa_defs.h>       /* _ILP32 */
  43 #include "libm.h"
  44
  45 #if defined(_ILP32)
  46 long
  47 lrint(double x) {
  48         /*
  49          * Note: The following code works on x86 (in the default rounding
  50          * precision mode), but one should just use the fistpl instruction
  51          * instead.
  52          */
  53         union {
  54                 unsigned i[2];
  55                 double d;
  56         } xx, yy;
  57         unsigned hx;
  58
  59         xx.d = x;
  60         hx = xx.i[HIWORD] & ~0x80000000;
  61         if (hx < 0x43300000) { /* |x| < 2^52 */
  62                 /* add and subtract a power of two to round x to an integer */
  63 #if defined(__sparc)
  64                 yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43300000;
  65 #elif defined(__x86)
  66                 yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43e00000;
  67 #else
  68 #error Unknown architecture
  69 #endif
  70                 yy.i[LOWORD] = 0;
  71                 x = (x + yy.d) - yy.d;
  72         }
  73
  74         /* now x is nan, inf, or integral */
  75         return ((long) x);
  76 }
  77 #else
  78 #error Unsupported architecture
  79 #endif  /* defined(_ILP32) */