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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: ADA CORE TECHNOLOGIES ANNOUNCES GNAT-TO-JAVA SYSTEM
Date: 1997/09/16
Message-ID: <dewar.874439071@merv>#1/1
X-Deja-AN: 273070385
References: <dewar.873998738@merv> <34196E8E.1790@gsfc.nasa.gov>
 <dewar.874165896@merv> <341D47EE.3804@gsfc.nasa.gov>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-09-16T00:00:00+00:00
List-Id: <comp.lang.ada>


Stephe said

<<<<I guess I need to read up on the JVM. I've been assuming it was at the
  same level as the UCSD Pascal P-machine; basically a virtual 32 bit
  processor, with operations like a current-generation RISC chip. I guess
  this is wrong.>>

Completely wrong, JVM is nothing like a conventional machine language

<<Yeah, and I can deliver a Working System Real Soon Now. I hoped I would
  be able to take your new backend, and make it generate assembler for my
  chip, instead of "assembler" for the JVM.

No, that's completely inappropriate.

<<Even if you are not replacing gcc for real processors now, maybe you
  could try to make it possible to eventually use this backend as a
  replacement for part of gcc (talk about vague requirements!). We need to
  get away from K&R in the core of our compilers sometime!>>

It is obvious from this that you know very little about gcc, so while you
are reading up on JVM, read up on GCC too. The GCC backend has nothing to
do with C or K&R per se, it is a code generator that can take input from
multiple front ends (one is the GNU C compiler, one is GNAT, there are
several others), and generate output for a very large variety of
architectures.

Basically if you want GCC to generate code for a new target, you just write
a formal definition of the instruction set for that architecture, called
a machine configuration file, and everything else is automatic. Writing
these configuration files is quite a straightforward task once you are
familiar with the technical approach.

<<I guess this is what Intermetrics has; the AdaMagic front end
  accommodates several backends. Is that all written in Ada?>>

That's of interest to interface to existing foreign front ends, especially
if you want to keep them proprietary, but for generating code for a new
machine there is no advantage unless you have a code generator in your
pocket that for some reason you want to use instead of GCC. But it sounds
like in fact GCC is exactly what you are looking for, a code generator
that can generate code for a variety of machines using the GNAT front end.

There is no point in trying to make the Java system do what you want, as
you will see if you do your homework in both areas :-)