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From: jkenton@pinocchio.encore.com (Jeff Kenton)
Newsgroups: comp.sys.m88k
Subject: Re: 88000 assembly code
Message-ID: <12315@encore.Encore.COM>
Date: 27 Jul 90 13:28:39 GMT
References: <1872@hsi86.hsi.UUCP>
Sender: news@Encore.COM
Lines: 39

From article <1872@hsi86.hsi.UUCP>, by hogue@hsi.UUCP (Jim Hogue):
> I am having troule with the gnu C compiler on an AViiON.  Specifically
> I am running DG-UX (version 4.30) and with the optimiser on, the
> compiler produces code that the assembler barfs on.  The function is
> rather large and I would like to narrow it down before I ask for
> detailed help.  But in the mean time I don't have any knowledge of nor
> texts that describe the 88000 assembler.  Question is what does br.n
> addr do?  Is it an unconditional branch or is it branch not equal to 0
> or something else?  As usual help is greatly appreaciated!
> 
> FYI, from memory the code generated is something like
> 
> 	br.n	addr1
> 	or	r1,r2,r3,0x1234
> addrn	add	r10,r2,0x400
> 
> The assembler complains that or instructions cannot have 4 operands!

The assembler is right (naturally) -- the compiler is producing broken
code.  "or" instructions, and many others, have only 3 operands.  None
has 4 operands, although some have 1 or 2 (or none).

The br.n instruction is an unconditional branch.  The ".n" causes the
"next" instruction (physically after the br.n) to be executed before
doing the branch.










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      jeff kenton  ---	temporarily at jkenton@pinocchio.encore.com	 
		   ---  always at (617) 894-4508  ---
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