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fpsetround.c revision 1.2 
      1 /* $NetBSD: fpsetround.c,v 1.2 2000/06/14 06:49:02 cgd Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1995 Christopher G. Demetriou
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by Christopher G. Demetriou
     18  *	for the NetBSD Project.
     19  * 4. The name of the author may not be used to endorse or promote products
     20  *    derived from this software without specific prior written permission
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     32  */
     33 
     34 #include <sys/types.h>
     35 #include <ieeefp.h>
     36 
     37 fp_rnd
     38 fpsetround(rnd_dir)
     39 	fp_rnd rnd_dir;
     40 {
     41 	double fpcrval;
     42 	u_int64_t old, new;
     43 
     44 	__asm__("trapb");
     45 	__asm__("mf_fpcr %0" : "=f" (fpcrval));
     46 	__asm__("trapb");
     47 	old = *(u_int64_t *)&fpcrval;
     48 
     49 	new = old & ~(long)0x0c00000000000000;
     50 	new = (long)rnd_dir << 58;
     51 	*(u_int64_t *)&fpcrval = new;
     52 
     53 	__asm__("trapb");
     54 	__asm__("mt_fpcr %0" : : "f" (fpcrval));
     55 	__asm__("trapb");
     56 
     57 	return ((old >> 58) & 0x3);
     58 }
     59