treelang fix for rs6000 / treelang not proper front end

[Fergus Henderson]

On 09-Jun-2003, Steven Bosscher <s.bosscher@student.tudelft.nl> wrote:
> I would also like do discuss the future of treelang.  It is a 
> neat small front end, but the more I look at it, the less I like it in 
> its current shape.  IMHO if it is to be an example front end, then it 
> should set a _good_ example.

I agree; however, even a merely mediocre example is still a lot better
than none.

> I had started working on a treelang-like front end that conforms to the 
> GCC conding style, targets GENERIC and is completely standalone.  It 
> produces a few non-GENERIC nodes in the parser to show how  lowering the 
> parse tree to GENERIC would work.  I wanted it to follows 
> sourcebuild.texi and frontend.texi to the letter.

That all sounds like a good idea.

> I also wanted the parser to build the parse tree using 'tree' and to 
> build funtions as trees.  I know you probably do not like parsing 
> directly into 'tree', because treelang now shows how you can _not_ build 
> trees and still interface with GCC, like most existing front ends (G77, 
> G95, Ada, COBOL and a few others) actually do.  But using trees from the 
> start makes the front end much smaller. I used trees because I just 
> wanted to see how it would look, but I can see why you choose 
> differently.  It is a matter of what you want to show with treelang.

My preferance is for a separate parse tree.  Even though this may make
the source code longer, I still think this is better, because I think
the separation makes it easier to understand the GCC front-end interface.
Also this approach scales better to real systems and is the sort of
approach that we should encourage for new front-ends.

> So, what do we _want_ to show with treelang?  What is the function of 
> treelang within GCC and what implications does that have for its design?

The purpose of treelang within GCC, IMHO, is to provide a simple but
complete and working didactic example of a front-end, in order to make it
easier for people to understand the front-end interface, and to provide
something that people writing a new front-end can use as a model on
which to base their front-ends.

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.