4.4BSD/usr/src/sys/tahoe/math/Kfnorm.s

/*-
 * Copyright (c) 1985 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Computer Consoles 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.
 *
 *	@(#)Kfnorm.s	7.1 (Berkeley) 12/6/90
 */

#include "../math/fp.h"
#include "../math/Kfp.h"
#include "../tahoe/SYS.h"

	.text
ENTRY(Kfnorm, R6|R5|R4|R3|R2)
				# clrl	r1
	movl	r0,r4		# copy to temporary.
	jneq	inr0
	movl	r1,r5
	clrl	r3		# r3 - pos of m.s.b
inr1:	ffs	r5,r6
	incl	r6
	addl2	r6,r3
	shrl	r6,r5,r5
	jneq	inr1
	cmpl	$0,r3
	jeql	retzero
	jmp	cmpshift
inr0:	movl	$32,r3
inr00:	ffs	r4,r6
	incl	r6
	addl2	r6,r3
	shrl	r6,r4,r4
	jneq	inr00

cmpshift:
				# compute the shift (r4).
	subl3	r3,$HID_R0R1,r4
	jlss	shiftr		# if less then zero we shift right.
	shlq	r4,r0,r0	# else we shift left.
	subl2	r4,r2		# uodate exponent.
	jleq	underflow	# if less then 0 (biased) it is underflow.
	jmp	combine		# go to combine exponent and fraction.
shiftr:
	mnegl	r4,r4
	shrq	r4,r0,r0	# shift right.
	addl2	r4,r2		# update exponent
	cmpl	r2,$256
	jgeq	overflow	# check for overflow.
combine:
	andl2	$CLEARHID,r0	# clear the hidden bit.
	shal	$EXPSHIFT,r2,r2	# shift the exponent to its proper place.
	orl2	r2,r0
	ret

underflow:
	clrl	r0
	orl2	$HFS_UNDF,*4(fp)	
	ret

overflow:
	orl2	$HFS_OVF,*4(fp) 	
	ret
retzero:
	clrl	r0
	clrl	r1
	ret