usr/src/lib/libc/amd64/fp/fpsetround.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 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
  28 /*      Copyright (c) 1988 AT&T */
  29 /*        All Rights Reserved   */
  30
  31 #pragma ident   "%Z%%M% %I%     %E% SMI"
  32
  33 #pragma weak _fpsetround = fpsetround
  34
  35 #include "lint.h"
  36 #include <ieeefp.h>
  37 #include "fp.h"
  38
  39 extern void     _getmxcsr(int *), _putmxcsr(int);
  40
  41 fp_rnd
  42 fpsetround(fp_rnd newrnd)
  43 {
  44         struct _cw87 cw;
  45         fp_rnd oldrnd;
  46         int     mxcsr;
  47
  48         newrnd &= 0x3;  /* mask off all ubt last 2 bits */
  49         _getcw(&cw);
  50         oldrnd = (fp_rnd)cw.rnd;
  51         cw.rnd = newrnd;
  52         _putcw(cw);
  53         _getmxcsr(&mxcsr);
  54         mxcsr = (mxcsr & ~0x6000) | ((int)newrnd << 13);
  55         _putmxcsr(mxcsr);
  56         return (oldrnd);
  57 }