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From: Ada2001 <ada2001@my-deja.com>
Subject: Re: GNAT & GCC performace (bad news)
Date: 1999/12/08
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In article <82kumr$jrd$1@nnrp1.deja.com>,
  Robert Dewar <robert_dewar@my-deja.com> wrote:
>
> 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).
>

Can you give us an overview of how JGNAT differs from regular GNAT with
respect to dependence on gcc? I have the impression, quite possibly
wrong, that all of JGNAT including the bytecode generator is written in
Ada and that it doesn't depend on gcc.  Is that correct?

F. Britt Snodgrass


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