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From: jlw@ariel.UUCP (J.WOOD)
Newsgroups: net.arch
Subject: Re: Re: Cleverness in the WE-32001
Message-ID: <996@ariel.UUCP>
Date: Sat, 27-Jul-85 09:50:05 EDT
Article-I.D.: ariel.996
Posted: Sat Jul 27 09:50:05 1985
Date-Received: Wed, 31-Jul-85 02:15:07 EDT
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Organization: AT&T-ISL, Holmdel, NJ
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> Mr Long comments that the WE-32001 contains a pc displacement addressing
> mode that could be used to effect position independent code.  Yes it
> exists, and I don't know specifically why the assembler doesn't use it.
> The only possibilities that come to mind are that it might be easier
> for the assembler to generate the absolute address mode, or that the
> code might execute faster.  If you look closely at the operand
> descripter encodings (at least for the 32100, I'm assuming that the
> 32001 is the same) you'll you'll see that using the PC with some addressing
> modes causes special things to happen.

This also may be a holdover from the past.  Most of the hardware
implementations that I know about which use the 8086 and its
descendants have separate I and D space.  In that case PC relative
addressing for data objects won't work.  Perhaps the Assembler
was written by the same crowd.



					Joseph L. Wood, III
					AT&T Information Systems
					Laboratories, Holmdel
					(201) 834-3759
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