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From: deven@pawl.rpi.edu (Deven Corzine)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga compiler optimizing test
Message-ID: <DEVEN.89Mar3035559@daniel.pawl.rpi.edu>
Date: 3 Mar 89 08:55:59 GMT
References: <3531@sdsu.UUCP>
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In-reply-to: lindwall@sdsu.UUCP's message of 2 Mar 89 07:00:30 GMT

Lattice C V5.00 generated similar code; it did not factor the
expression and do the shift once only.  (with or without the global
optimizer.)  with your example, the compiler complained about
uninitialized automatic variables and the optimizer simply killed the
whold thing as being dead code.  recoded as:

test(x,y);
int x,y;
{
   return(x*8-y*8);
}

compiled with:

lc -O -v test.c

nothing complained, produced code was:

	link a5,#0000		; (exactly what does this do?)
				; [something w/stack]
	move.l 000c(a5),d0	; x
	asl.l #3,d0		; x*8
	move.l 0008(a5),d1	; y
	asl.l #3,d1		; y*8
	sub.l d0,d1		; x*8-y*8
	move.l d1,d0		; return x*8-y*8
	unlk a5			; undo the link
	rts			; return

Deven
--
------- shadow@pawl.rpi.edu ------- Deven Thomas Corzine ---------------------
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