%	Author M.Ruckert

sbit		GREG	1<<63	the sign bit
exceptions 	GREG 	0	holds the exception bits


xt
xs
xe
xf
round		IS
yt		IS	Y  category, zero, denormal, normal, infinite, NaN
ys
ye
yf
zt
zs	IS	$
ze
zf
round	IS	

tmp	IS


Fsub	GET	zs,rZZ		Floating point subtraction
	XOR	zs,sbit		Change sign of operand
	PUT	zs,rZZ		
Fadd	GET	return,rJ	
	GET	ys,rYY		Floating point addition
	GET	zs,rZZ
	SLU	ye,ys,1; SLU	ze,zs,1	remove sign bit
	CMPU	tmp,ye,ze	\ul{\it A2.~Assume $e_y \ge e_z$}
	BNP	tmp,1F
	SET	tmp,ys; SET ys,zs; SET zs,tmp swap $y$ and $z$
	PUT	rZZ,zs
	PUSHJ	yt,funpack	\ul{\it A1.~Unpack.}
	GET	zs,rZZ		
	PUSHJ	zt,funpack


Add nonzero nubers and return
       SET  	xs,ys
       SET	xe,ye


    	SUB 	   d,ye,ze	\ul{\it A5.~Scale right.}
	CMP	   tmp,d,2
	BP	   tmp,1F
	SRU	   zf,zf,d	exact result
	JMP	   2F
1H	CMP	   tmp,d,53	tricky but OK
	BNP	   tmp,1F
	SET	   zf,1
	JMP	   2F
1H	CMP	   tmp,ys,zs
	BZ	   tmp,1F
	SUB	   d,d,1
	SUB	   xe,xe,1
	SLU	   yf,yf,1
1H	SET	   tmp,zf
	SRU	   zf,zf,d
	SLU	   tmp+1,zf,d
	CMPU	   tmp,tmp,tmp+1
	CZSNZ	   tmp,tmp,1		this is different than MMIX-ARITH 49.
	OR	   zf,zf,1
2H	CMP	   tmp,ys,yz			\ul{\it A6.~Add.}
	BNZ	   tmp,subtract
	ADDU	   xf,yf,zf	
        SRU	   tmp,xf,55
	BP	   tmp,3F
	ADD	   xe,xe,1
	SRU	   xf,xf,1
	JMP	   3F
subtract SUBU	   xf,yf,zf	
        SRU	   tmp,xf,55
	BP	   tmp,3F
	ADD	   xe,xe,1
	SRU	   xf,xf,1
	JMP	   1F
	ADD	   xe,xe,1
	AND	   tmp,xf,1		sticky bit
	SRU	   xf,xf,1
	OR	   xf,xf,tmp

1H	SRU	   tmp,xf,54
	BP	   tmp,3F
	SUB	   xe,xe,1
	SLU	   xf,xf,1
	JMP	   1B
	
3H	PUSHJ	xt,fpack

Done	GET	tmp,rXX
	OR	tmp,tmp,exceptions
	PUT	tmp,rXX
	PUT	rJ,return
	POP	0,0		ready to \.{RESUME}