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From: darrell@sdcsvax.UUCP (Darrell Long)
Newsgroups: net.arch
Subject: The little assembler that lies...
Message-ID: <893@sdcsvax.UUCP>
Date: Wed, 29-May-85 00:09:15 EDT
Article-I.D.: sdcsvax.893
Posted: Wed May 29 00:09:15 1985
Date-Received: Sat, 1-Jun-85 12:11:00 EDT
Organization: EECS Dept. U.C. San Diego
Lines: 32


     Well folks, here I am again with  3B-2  assembler  com-
ments,  questions  and  gripes.   My  topic  tonight  is the
RESTORE instruction.


     The  BELLMAC-32  processor  (a.k.a.  WE-3200x)  has  an
instruction,  called  RESTORE which restores a set of regis-
ters from the stack.   This  instruction  really  exists,  I
typed  in  the  hex  code for it.  However, the as assembler
insists on mapping  this  single  instruction  to  up  to  7
instructions.

        RESTORE    =>    MOVAW
                         POPW
                         ...
                         POPW

     This is a strange thing for an assembler to do.  Is  it
done  so  that the same assembler can be used on a processor
which does not have the RESTORE instruction?  Or is it  that
the  sequence  of POPW instructions are actually faster than
the RESTORE (if this is true then why waste chip space  with
the RESTORE instruction)?

-- 
Darrell Long
Department of Electrical Engineering and Computer Science
University of California, San Diego

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