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From: jack@hp-dcde.UUCP
Newsgroups: net.micro.68k
Subject: Re: Does anyone have nargs() for the 680 - (nf)
Message-ID: <3567@hp-pcd.UUCP>
Date: Sat, 31-Dec-83 03:27:35 EST
Article-I.D.: hp-pcd.3567
Posted: Sat Dec 31 03:27:35 1983
Date-Received: Wed, 4-Jan-84 03:31:30 EST
Sender: notes_gateway@hp-pcd.UUCP
Organization: Hewlett-Packard, Fort Collins, CO
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#R:utcsrgv:-298800:hp-dcde:21100001:000:926
hp-dcde!jack    Dec 28 11:16:00 1983

re: nargs

Remember, though, it won't always be an ADD instruction after the jsr.
For example, our optimizer makes the transformation:

	move.l	d0,-(sp)	=>	move.l	d0,-(sp)
	move.l	d1,-(sp)	=>	move.l	d1,-(sp)
	move.l	d2,-(sp)	=>	move.l	d2,-(sp)
	jbsr	gamma		=>	jbsr	gamma
	add.l	#12,sp		=>	lea	12(sp),sp

Or perhaps:

	move.l	d0,-(sp)	=>	move.l	d0,-(sp)
	jbsr	alpha		=>	jbsr	alpha
	addq.l	#4,sp		=>
	move.l	d0,-(sp)	=>	move.l	d0,(sp)		no decrement
	jbsr	beta		=>	jbsr	beta
	addq.l	#4,sp		=>	addq.l	#4,sp

Timings:
	add.l	#12,sp		8 cycles, 6 bytes	(really adda)
	add.w	#12,sp		12 cycles, 4 bytes	(really adda)
	lea	12(sp),sp	8 cycles, 4 bytes

Of course, nargs could be enhanced to check for lea also,
and hence work for the gamma case, but the alpha case looks hopeless.


					      -Jack Applin
					      Optimizing himself to death at:	
					      Hewlett-Packard
					      Ft. Collins, CO
					      (hplabs!hp-dcd!jack)