From: leathm AT solwarra DOT gbrmpa DOT gov DOT au (Leath Muller)
Message-Id: <199703110238.MAA29246@solwarra.gbrmpa.gov.au>
Subject: Re: Interesting benchmark results
To: chambersb AT juno DOT com (Benjamin D Chambers)
Date: Tue, 11 Mar 1997 12:38:55 +1000 (EST)
Cc: djgpp AT delorie DOT com
In-Reply-To: <19970310.174935.10167.11.chambersb@juno.com> from "Benjamin D Chambers" at Mar 10, 97 08:46:27 pm
Content-Type: text

> OTOH, people using a Pentium might be _hurt_ a lot more than he is by
> using -O3.  AFAIK, the Pentium will only go superscalar if the code
> _is_already_in_the_cache_and_has_been_executed.  This imposes quite a
> limit on things; ie you have to keep code size small (which is the
> opposite of -O3) and looping (which is kind of the opposite of -O3 :)  Of
> course, branches can wreak havoc too... The general rule is, there _is_
> no general rule.  Try everything out for each individual program to find
> out for sure.

Ummm...basically, to my knowledge anyway, and by my understanding of the
doc's, your completely wrong. :)  Code always goes superscalar if it can
because its _always_ in the cache (code _has_ to be in the cache to
execute to start with, no?) and it will go superscalar if executed the
first time too. 

Branches can be predicted following some basic rules...

Have your read the Pentium Programmers Guide? Its really cool if you haven't,
and if you have, where does it say this stuff?

Leathal.