treelang fix for rs6000 / treelang not proper front end

[Steven Bosscher]

Tim Josling wrote:

> Steven Bosscher wrote:
>
>>
>>
>> Remember that in an earlier discussion we had, I already _did_
>> offer you to make treelang 'proper' for a tree-ssa, and to
>> take over as a maintainer for that branch so that you would
>> only have to take care of mainline?  That was only a couple
>> of months ago, and you then said you didn't think it was
>> worth the effort.
>>
>> Gr.
>> Steven
>>
>
>
> No I don't remember. What I seem to remember is a suggestion that I 
> update it. I had a look at doing it but foundered on lack of 
> documentation.
>
> However if the offer is still open, I accept. This would certainly be 
> a good step forward. 

Sure, my offer still stands.

I am trying to update Fergus' patch to apply to the tree-ssa branch now 
(it needs some re-writing here and there).  I will try to make it work 
with mainline as well if you like.

However, 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.  Actually I had already sort of given up on 
treelang.

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.
(Unfortunately most if it got lost when my computer went up in flames...)

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.

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?

Gr.
Steven