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      1 /*	$NetBSD: divsim.c,v 1.5 2012/02/04 17:03:09 skrll Exp $	*/
      2 
      3 /*	$OpenBSD: divsim.c,v 1.4 2001/03/29 03:58:18 mickey Exp $	*/
      4 
      5 /*
      6  * Copyright 1996 1995 by Open Software Foundation, Inc.
      7  *              All Rights Reserved
      8  *
      9  * Permission to use, copy, modify, and distribute this software and
     10  * its documentation for any purpose and without fee is hereby granted,
     11  * provided that the above copyright notice appears in all copies and
     12  * that both the copyright notice and this permission notice appear in
     13  * supporting documentation.
     14  *
     15  * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
     16  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     17  * FOR A PARTICULAR PURPOSE.
     18  *
     19  * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
     20  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
     21  * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
     22  * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
     23  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     24  *
     25  */
     26 /*
     27  * pmk1.1
     28  */
     29 /*
     30  * (c) Copyright 1986 HEWLETT-PACKARD COMPANY
     31  *
     32  * To anyone who acknowledges that this file is provided "AS IS"
     33  * without any express or implied warranty:
     34  *     permission to use, copy, modify, and distribute this file
     35  * for any purpose is hereby granted without fee, provided that
     36  * the above copyright notice and this notice appears in all
     37  * copies, and that the name of Hewlett-Packard Company not be
     38  * used in advertising or publicity pertaining to distribution
     39  * of the software without specific, written prior permission.
     40  * Hewlett-Packard Company makes no representations about the
     41  * suitability of this software for any purpose.
     42  */
     43 
     44 #include <sys/cdefs.h>
     45 __KERNEL_RCSID(0, "$NetBSD: divsim.c,v 1.5 2012/02/04 17:03:09 skrll Exp $");
     46 
     47 #include "md.h"
     48 
     49 void
     50 divsim(int opnd1, int opnd2, struct mdsfu_register *result)
     51 {
     52 	int sign, op1_sign;
     53 
     54 	/* check divisor for zero */
     55 	if (opnd2 == 0) {
     56 		overflow = true;
     57 		return;
     58 	}
     59 
     60 	/* get sign of result */
     61 	sign = opnd1 ^ opnd2;
     62 
     63 	/* get absolute value of operands */
     64 	if (opnd1 < 0) {
     65 		opnd1 = -opnd1;
     66 		op1_sign = true;
     67 	}
     68 	else op1_sign = false;
     69 	if (opnd2 < 0) opnd2 = -opnd2;
     70 
     71 	/* check for opnd2 == -2**31 */
     72 	if (opnd2 < 0) {
     73 		if (opnd1 == opnd2) {
     74 			result_hi = 0;	/* remainder = 0 */
     75 			result_lo = 1;
     76 		}
     77 		else {
     78 			result_hi = opnd1;	/* remainder = opnd1 */
     79 			result_lo = 0;
     80 		}
     81 	}
     82 	else {
     83 		/* do the divide */
     84 		divu(0,opnd1,opnd2,result);
     85 
     86 		/*
     87 		 * check for overflow
     88 		 *
     89 		 * at this point, the only way we can get overflow
     90 		 * is with opnd1 = -2**31 and opnd2 = -1
     91 		 */
     92 		if (sign>0 && result_lo<0) {
     93 			overflow = true;
     94 			return;
     95 		}
     96 	}
     97 	overflow = false;
     98 
     99 	/* return positive residue */
    100 	if (op1_sign && result_hi) {
    101 		result_hi = opnd2 - result_hi;
    102 		if (++result_lo < 0) {
    103 			overflow = true;
    104 			return;
    105 		}
    106 	}
    107 
    108 	/* return appropriately signed result */
    109 	if (sign<0) result_lo = -result_lo;
    110 	return;
    111 }
    112