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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: GNAT & GCC performace (bad news)
Date: 1999/12/08
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In article <384D4A80.DBAA4E67@averstar.com>,
  Tucker Taft <stt@averstar.com> wrote:

> With our current translation approach, our belief is that
> we would not do any better by connecting into the C back end
> directly, bypassing the C front end.

I definitely agree with this. The problems I mentioned are all
ones that are fundamental to a C back end, and it seems
perfectly appropriate to attach to the front end by generating
C. Either the front end does no optimization, in which case
it's a wash, or it optimizes, in which case you are ahead.

People often assume that gcc is a C back end, but actually at
this stage it is a multi-language back end. When we first
wrote GNAT, gcc did not know any Ada at all, and we could have
linked to the existing gcc backend by doing the same kind of
Ada-to-C mapping as is done by the Intermetrics front end
(although at least we had efficient nested procedures, because
GNU C has nested functions).

But we decided this would lose too much efficiency for some
constructions, and we modified the back end of GCC to accomodate
Ada more closely. See the paper "Teaching GCC Ada" [or somesuch
title] in a recent Tri-Ada conference (sorry, do not have exact
reference).


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