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      1 /* $NetBSD: flt_rounds.c,v 1.10 2014/08/03 19:14:24 wiz 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 1.10 2014/08/03 19:14:24 wiz Exp $");
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <sys/types.h>
     43 #include <machine/ieeefp.h>
     44 #include <machine/float.h>
     45 
     46 /*
     47  * These come from <float.h> definition
     48  */
     49 #define	FLT_ROUND_MAP \
     50 	( (0 << (FP_RZ*2))	/* round to zero */			\
     51 	| (1 << (FP_RN*2))	/* round to nearest */			\
     52 	| (3 << (FP_RM*2))	/* round to negative infinity */	\
     53 	| (2 << (FP_RP*2)))	/* round to positive infinity */
     54 
     55 int
     56 __flt_rounds(void)
     57 {
     58 	union {
     59 		double d;
     60 		uint64_t u64;
     61 	} fpcrval;
     62 	uint64_t old;
     63 
     64 	__asm("excb; mf_fpcr %0; excb" : "=f" (fpcrval.d));
     65 	old = (fpcrval.u64 >> 58) & 3;
     66 
     67 	return (FLT_ROUND_MAP >> (old << 1)) & 3;
     68 }
     69