Re: New GNAT ports (was Re: Ada and Automotive Industry)

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Richard said

"I've poked around in the GNAT sources from time to time, but have never
studied the whole thing.  People who _have_ studied it:  how long do you
think it would take to understand the GNAT front end well enough to
make an informed judgement about the difficulty of writing a non-GCC
back end for it?"

The front end of GNAT is pretty accessible. Read the documentation in
sinfo and einfo to get a definition of the tree that is produced.
Writing a production quality backend for any machine from scratch is
a big project, of the order of person years for someone who knows what
they are doing. Adapting an existing backend (if one is available that
can be GPL'ed) is certainly a possibility, although sometimes clashes
in assumptions can make such a project harder than expected. Note that
the Ada Magic front end is more deliberately setup to provide for
interfacing with multiple backends (this is obviously not a criterion
for GNAT, since the assumption is that only one backend, GCC, will be
used).

Certainly building a small trial code generator hooked into the backend
of GNAT is practical. I am planning on having my students in my compiler
class do that this coming semester.