From: kilgallen@eisner.decus.org (Larry Kilgallen)
Subject: Re: GNAT & GCC performace (bad news)
Date: 1999/12/06
Date: 1999-12-06T00:00:00+00:00 [thread overview]
Message-ID: <1999Dec6.073729.1@eisner> (raw)
In-Reply-To: 82fgh2$mt3$1@nnrp1.deja.com
In article <82fgh2$mt3$1@nnrp1.deja.com>, Robert Dewar <dewar@gnat.com> writes:
> But there is a huge difference between emitting assembly
> language, which is just a 1-1 shorthand for machine language,
> and is therefore obviously equivalent from a performance
> point of view to emitting machine language (*)
>
> and emitting C, where there are two significant problems:
>
> 1. It may be impossible to emit efficient code for a given
> construct in the intermediate high level language (e.g.
> exceptions, compiler checks, various other things ...)
>
> 2. The C compiler will introduce inefficiencies of its own
> for the generated code.
The C compiler may also introduce optimizations specific to
the machine that were not provided by the earlier compiler.
If you read the propaganda for the Averstar Ada-to-C project,
an aim seems to be to leverage effort machine manufacturers
are already putting into optimizing their C compilers. Of
course there are other optimizations that can only be done
well with the full Ada semantics.
On a theoretical basis, it is possible to do anything in
machine language one can do in a higher level language.
However I believe that optimizing for various versions of
a particular chip is higher priority for the folks pushing
that chip than they are for the folks trying to provide a
multi-platform compiler (regardless of whether it emits
assembly language or C code).
Larry Kilgallen
next prev parent reply other threads:[~1999-12-06 0:00 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-02 0:00 GNAT & GCC performace (bad news) Harald Schmidt
1999-12-02 0:00 ` Dmitriy Anisimkov
1999-12-02 0:00 ` nabbasi
1999-12-02 0:00 ` James E. Hopper
1999-12-03 0:00 ` Robert A Duff
1999-12-04 0:00 ` Robert Dewar
1999-12-04 0:00 ` Harald Schmidt
1999-12-02 0:00 ` David Starner
1999-12-02 0:00 ` Tucker Taft
1999-12-03 0:00 ` Geoff Bull
1999-12-03 0:00 ` Larry Kilgallen
1999-12-06 0:00 ` Robert Dewar
1999-12-06 0:00 ` Larry Kilgallen [this message]
1999-12-06 0:00 ` Robert A Duff
1999-12-07 0:00 ` Robert Dewar
1999-12-07 0:00 ` Tucker Taft
1999-12-08 0:00 ` Robert Dewar
1999-12-08 0:00 ` Ada2001
1999-12-09 0:00 ` Wes Groleau
1999-12-10 0:00 ` Robert Dewar
1999-12-10 0:00 ` Arthur Evans Jr
1999-12-11 0:00 ` Robert Dewar
1999-12-17 0:00 ` Richard Kenner
1999-12-07 0:00 ` Robert Dewar
1999-12-03 0:00 ` Geoff Bull
1999-12-03 0:00 ` Mats Weber
1999-12-03 0:00 ` Robert Dewar
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