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ashrdi3.c revision 1.1 
      1 /*	$NetBSD: ashrdi3.c,v 1.1 2005/12/20 19:28:51 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1992, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This software was developed by the Computer Systems Engineering group
      8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
      9  * contributed to Berkeley.
     10  *
     11  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright
     17  *    notice, this list of conditions and the following disclaimer in the
     18  *    documentation and/or other materials provided with the distribution.
     19  * 3. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)ashrdi3.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: ashrdi3.c,v 1.1 2005/12/20 19:28:51 christos Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "quad.h"
     46 
     47 /*
     48  * Shift a (signed) quad value right (arithmetic shift right).
     49  */
     50 quad_t
     51 __ashrdi3(a, shift)
     52 	quad_t a;
     53 	qshift_t shift;
     54 {
     55 	union uu aa;
     56 
     57 	if (shift == 0)
     58 		return(a);
     59 	aa.q = a;
     60 	if (shift >= INT_BITS) {
     61 		int s;
     62 
     63 		/*
     64 		 * Smear bits rightward using the machine's right-shift
     65 		 * method, whether that is sign extension or zero fill,
     66 		 * to get the `sign word' s.  Note that shifting by
     67 		 * INT_BITS is undefined, so we shift (INT_BITS-1),
     68 		 * then 1 more, to get our answer.
     69 		 */
     70 		/* LINTED inherits machine dependency */
     71 		s = (aa.sl[H] >> (INT_BITS - 1)) >> 1;
     72 		/* LINTED inherits machine dependency*/
     73 		aa.ul[L] = aa.sl[H] >> (shift - INT_BITS);
     74 		aa.ul[H] = s;
     75 	} else {
     76 		aa.ul[L] = (aa.ul[L] >> shift) |
     77 		    (aa.ul[H] << (INT_BITS - shift));
     78 		/* LINTED inherits machine dependency */
     79 		aa.sl[H] >>= shift;
     80 	}
     81 	return (aa.q);
     82 }
     83