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flt_rounds.c revision 1.7 
      1 /* $NetBSD: flt_rounds.c,v 1.7 2005/06/12 05:21:25 lukem 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 for the
     18  *          NetBSD Project.  See http://www.NetBSD.org/ for
     19  *          information about NetBSD.
     20  * 4. The name of the author may not be used to endorse or promote products
     21  *    derived from this software without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     33  *
     34  * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
     35  */
     36 
     37 #include <sys/cdefs.h>
     38 #if defined(LIBC_SCCS) && !defined(lint)
     39 __RCSID("$NetBSD: flt_rounds.c,v 1.7 2005/06/12 05:21:25 lukem Exp $");
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <sys/types.h>
     43 #include <machine/float.h>
     44 
     45 static const int map[] = {
     46 	0,	/* round to zero */
     47 	3,	/* round to negative infinity */
     48 	1,	/* round to nearest */
     49 	2	/* round to positive infinity */
     50 };
     51 
     52 int
     53 __flt_rounds()
     54 {
     55 	double fpcrval;
     56 	u_int64_t old;
     57 
     58 	__asm__("trapb");
     59 	__asm__("mf_fpcr %0" : "=f" (fpcrval));
     60 	__asm__("trapb");
     61 	old = *(u_int64_t *)(void *)&fpcrval;
     62 
     63 	return map[(old >> 58) & 0x3];
     64 }
     65