urem.s

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Donn Seeley at UUNET Technologies, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
	.asciz "@(#)urem.s	8.1 (Berkeley) 6/4/93"
#endif /* LIBC_SCCS and not lint */

#include "DEFS.h"

/*
 * Unsigned modulus, PCC flavor.
 * urem() takes an ordinary dividend/divisor pair;
 * aurem() takes a pointer to a dividend and an ordinary divisor.
 */

#define	DIVIDEND	4(ap)
#define	DIVISOR		8(ap)

ASENTRY(urem,0)
	movl	DIVISOR,r2
	jlss	Leasy		# big divisor: settle by comparison
	movl	DIVIDEND,r0
	jlss	Lhard		# big dividend: need extended division
	divl3	r2,r0,r1	# small divisor and dividend: signed modulus
	mull2	r2,r1
	subl2	r1,r0
	ret
Lhard:
	clrl	r1
	ediv	r2,r0,r1,r0
	ret
Leasy:
	subl3	r2,DIVIDEND,r0
	jcc	Ldifference	# if divisor goes in once, return difference
	movl	DIVIDEND,r0	# if divisor is bigger, return dividend
Ldifference:
	ret

ASENTRY(aurem,0)
	movl	DIVIDEND,r3
	movl	DIVISOR,r2
	jlss	La_easy		# big divisor: settle by comparison
	movl	(r3),r0
	jlss	La_hard		# big dividend: need extended division
	divl3	r2,r0,r1	# small divisor and dividend: signed modulus
	mull2	r2,r1
	subl2	r1,r0
	movl	r0,(r3)		# leave the value of the assignment in r0
	ret
La_hard:
	clrl	r1
	ediv	r2,r0,r1,r0
	movl	r0,(r3)
	ret
La_easy:
	subl3	r2,(r3),r0
	jcs	La_dividend	# if divisor is bigger, leave dividend alone
	movl	r0,(r3)		# if divisor goes in once, store difference
	ret
La_dividend:
	movl	(r3),r0
	ret