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From: pkl@ee.mu.OZ.AU (Peter  LAWREY)
Newsgroups: comp.arch
Subject: Re: skip instructions
Message-ID: <1991May17.021324.18135@mulga.cs.mu.OZ.AU>
Date: 17 May 91 02:13:24 GMT
References: <1991May05.174307.8952@iecc.cambridge.ma.us> <1991May10.004650.7258@sbcs.sunysb.edu> <12162@mentor.cc.purdue.edu>
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Organization: University of Melbourne, EE Engineering
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In article <12162@mentor.cc.purdue.edu> hrubin@pop.stat.purdue.edu (Herman Rubin) writes:
>In article <1991May10.004650.7258@sbcs.sunysb.edu>, jallen@eeserv1.ic.sunysb.edu (Joseph Allen) writes:
>> In article <1991May05.174307.8952@iecc.cambridge.ma.us> johnl@iecc.cambridge.ma.us (John R. Levine) writes:
>> >In article <1182@opus.NMSU.Edu> jthomas@nmsu.edu (James Thomas) writes:
>
>Why get rid of condition flags?  Other than the condition register, they take

Condition flags are difficult to handle with out of order execution, interupts.
etc. To hold a condition you must save the PC,IR and the Condtion codes
for each stage of your pipeline. Also such things as multi-word operations are
made very rarely. You can have a trap on overflow or skip if no overflow
instruction that avoid these. But this occurs rarely in most programs.