Re: [9fans] Rant (was Re: Plan9 and Ada95?)

["Thomas Bushnell, BSG" <tb+usenet@becket.net>]

forsyth@vitanuova.com writes:

> by `if gnat is structured so as to allow another ... in principle',
> i meant, it has some internal representation of the Ada program that
> is at or near a useful level for code generation, before it produces RTL.
> if it is producing RTL directly from a basic parse tree,
> you'll have your work cut out.

Yes, that's true.  Most GCC front ends (and I'm sure gnat is the same
here) produce nice parse trees and generate code from those.  The
generation of the parse tree is, in principle, not tightly coupled
with anything to do with code generation.

However, the parse trees are usually partial (for example, the idea of
parsing a whole C file at once died a long time ago), and there may be
a lot of niggling little dependencies, since nobody's bothered to try
and separate the parts out that way.

Some people have tried to take the bison parser description files from
GCC and use them for other purposes as well, with varying degrees of
success.