kaddf.s

早期freebsd实现

/*-
 * 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.
 *
 *	@(#)Kaddf.s	7.1 (Berkeley) 12/6/90
 */

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

/*
 * _Kaddf(acc_most,acc_least,op_most,op_least,hfs)
 */
	.text
ENTRY(Kaddf, R10|R9|R8|R7|R6|R5|R4|R3|R2)
/*
 * see which operand has a greater exponent
 * The greater one will be fetched into r0,r1,r2,r3.
 * r0,r1 - 'pure' fraction, r2 - exponent, r3 - sign).
 * The smaller operand will be fetched into r4,r5,r6,r7.
 */
	tstl	4(fp)	# handle (a+b) where a and/or b = 0.0
	jneq	next
	movl	$0,r1
	movl	12(fp),r0
	ret
next:
	tstl	12(fp)
	jneq	doit
	movl	$0,r1
	movl	4(fp),r0
	ret
doit:
	andl3	$EXPMASK,4(fp),r0
	andl3	$EXPMASK,12(fp),r1
	cmpl	r0,r1
	jgtr	first_greater

	movl	12(fp),r0	# bigger operand to r0,r1
	movl	16(fp),r1

	movl	4(fp),r4	# smaller operand to r4,r5
	movl	8(fp),r5
	jmp	expo

first_greater:
	movl	4(fp),r0	# bigger operand to r0,r1
	movl	8(fp),r1

	movl	12(fp),r4	# smaller operand to r4,r5
	movl	16(fp),r5


 #
 #compute exponents:
 #
expo:
	andl3	$EXPMASK,r0,r2	# r2 will hold the exponent.
	shrl	$EXPSHIFT,r2,r2
	andl3	$EXPMASK,r4,r6	# r6 will hold the exponent.
	shrl	$EXPSHIFT,r6,r6
 #
 #compare the exponents:
 #
	subl3	r6,r2,r8
	jeql	signs
	cmpl	r8,$MAX_EXP_DIF
	jlss	signs
	ret			# return the bigger number.
 
 #
 #remember the signs:
 #
signs:
	clrl	r3
	bbc	$31,r0,sign2	# if negative remember it.
	incl	r3
sign2:
	clrl	r7
	bbc	$31,r4,frac	# if negative remember it.
	incl	r7
 #
 #compute 'pure' fraction:
 #
frac:
				# clear the non fraction parts.
	andl2	$(0!(EXPMASK | SIGNBIT)),r0
				# add the hidden bit.
	orl2	$(0!CLEARHID),r0
				# clear the non fraction parts.
	andl2	$(0!(EXPMASK | SIGNBIT)),r4
				# add the hidden bit.
	orl2	$(0!CLEARHID),r4

 #
 #shift the smaller operand:
 #
	shrq	r8,r4,r4
eql_exps:
	cmpl 	r3,r7
	jeql	add
	bbc	$0,r3,negr4r5
 #
 #negate the pair r0,r1:
 #
	clrl	r3
	mcoml	r1,r1
	clrl	r9		# r9 - carry flag.
	incl	r1
	bcc	comr0
	incl	r9		# remember the carry.
comr0:	mcoml	r0,r0
	bbc	$0,r9,add
	incl	r0

 #
 #add the fractions:
 #
add:
	clrl	r10 		# to remember the sign of the result.
	addl2	r5,r1
	adwc	r4,r0
	jgeq	norm		# if positive go to normelize.
	incl	r10		# else remember it and negate the result.
 #
 #negate the pair r0,r1:
 #
	clrl	r3
	mcoml	r1,r1
	clrl	r9		# r9 - carry flag.
	incl	r1
	bcc	comr00
	incl	r9		# remember the carry.
comr00:	mcoml	r0,r0
	bbc	$0,r9,norm
	incl	r0
norm:	pushl	20(fp)		# addr of returnen exception.
	callf	$8,_Kfnorm
 
 #
 #add the sign bit
 #
	bbs	$0,r10,negative
	bbs	$0,r3,negative
	ret
negative:
	orl2	$SIGNBIT,r0
	ret
 
 
 #
 #negate the pair r4,r5:
 #
negr4r5:
	clrl	r7
	mcoml	r5,r5
	clrl	r9		# r9 - carry flag.
	incl	r5
	bcc	comr4
	incl	r9		# remember the carry.
comr4:	mcoml	r4,r4
	bbc	$0,r9,add
	incl	r4
	jmp	add
 
 
	movl	r4,r0		# return the  smaller operand.
	movl	r5,r1
	ret