[GCC front end] add new TREE CODE

[GCC front end] add new TREE CODE

[charfi asma]

Hello,

I am developping my own gcc front end. My source language contains concepts that 
are not represented directly in C code.
to compile those elements, I think that I should add a new tree codes to my 
front end as C++ does for templates...
I think that I should also implement how to translate this new tree code in 
Gimple.
my question is : should I also care about how to translate those tree code al 
over the compiler chain: gimple --> ssa --> unssa --> rtl --> ass ...
did you suggest to follow an example of an existing front end that adds some 
tree code cause the C++ one seems to be mature and complete.

thank you very much

Asma

Re: [GCC front end] add new TREE CODE

[Ian Lance Taylor]

charfi asma <charfiasma@yahoo.fr> writes:

> I am developping my own gcc front end. My source language contains concepts that 
> are not represented directly in C code.
> to compile those elements, I think that I should add a new tree codes to my 
> front end as C++ does for templates...
> I think that I should also implement how to translate this new tree code in 
> Gimple.
> my question is : should I also care about how to translate those tree code al 
> over the compiler chain: gimple --> ssa --> unssa --> rtl --> ass ...
> did you suggest to follow an example of an existing front end that adds some 
> tree code cause the C++ one seems to be mature and complete.

First let me say that if your language is very different from C you
probably shouldn't be using trees at all.

But if your language is mostly like C then using trees is reasonable.
Even the C frontend itself has language-specific tree codes; see
c-family/c-common.def.  Or look at Objective C, at objc/objc-tree.def.

Ian

Re: [GCC front end] add new TREE CODE

[Andi Hellmund]

Hey Asma,
> my question is : should I also care about how to translate those tree code al
> over the compiler chain: gimple -->  ssa -->  unssa -->  rtl -->  ass ...
>    
The idea of GCC's modularization is that a front-end should maximally 
care about GIMPLE. All the other transformations are done by the 
middle-end.
> did you suggest to follow an example of an existing front end that adds some
> tree code cause the C++ one seems to be mature and complete.
>    
Yes, the C++ front-end uses quite a lot of own TREE codes, but I would 
then start with a very simple one and check how it "translates" the TREE 
codes into a GIMPLE sequence, e.g. by looking at the 'gimplify_expr' 
language hook which is 'cp_gimplify_expr' for C++.

I hope that helps. If you have any further question about the specific 
transformation from TREE codes to GIMPLE, just let us know ...

Andi

Re : [GCC front end] add new TREE CODE

[charfi asma]

----- Message d'origine ----
De : Andi Hellmund <mail@andihellmund.com>
À : charfi asma <charfiasma@yahoo.fr>
Cc : gcc-help@gcc.gnu.org
Envoyé le : Lun 14 février 2011, 18h 48min 26s
Objet : Re: [GCC front end] add new TREE CODE

Hey Asma,
> my question is : should I also care about how to translate those tree code al
> over the compiler chain: gimple -->  ssa -->  unssa -->  rtl -->  ass ...
>    
The idea of GCC's modularization is that a front-end should maximally care about 
GIMPLE. All the other transformations are done by the middle-end.
> did you suggest to follow an example of an existing front end that adds some
> tree code cause the C++ one seems to be mature and complete.
>    
Yes, the C++ front-end uses quite a lot of own TREE codes, but I would then 
start with a very simple one and check how it "translates" the TREE codes into a 
GIMPLE sequence, e.g. by looking at the 'gimplify_expr' language hook which is 
'cp_gimplify_expr' for C++.

I hope that helps. If you have any further question about the specific 
transformation from TREE codes to GIMPLE, just let us know ...

Andi

Hello,
thank you Andi and Ian for your help ;)

In fact, my language is moslty like C (var, function, call exp, if else, ...) 
but there is some difference, for example, I have State and transitions concepts 
which I can translate in C (set of states presented as enumerations and 
transitions as array of a defined type Transition which is a struct with source 
state, target state, guard, ...)
what I want to try, is to add a new tree codes to directly translate State, 
transtion, event, ... and do not use Array, enumeration of C language.


Ian said in his response that if my language is very different than C I should 
not use trees. Have you any idea of what I can use instead ? 


I look at the ghdl front end and I did not find vhdl-tree.def to see if they 
defined a new tree code for this fe.
I asked the question in their mailing list but I did not get an answer :(

I will probably  (as you suggested before) look at the cp front end and may be 
the java one also.

thank you again for your help

Asma

Re: Re : [GCC front end] add new TREE CODE

[Andi Hellmund]

>
> Ian said in his response that if my language is very different than C I should
> not use trees. Have you any idea of what I can use instead ?
>
>    
Hey Asma,

I'm not sure what Ian meant in detail, but I think that he wanted to say 
that you then shouldn't possibly use the TREE codes and 
tree-representation of GCC, but to use whatever intermediate 
representation is appropriate for your needs. If you would look up the 
literature, you would find tree-based structures as dominant 
intermediate structure, but most of these books then refer to 
C-syntax-like languages. Though, it is generally hard to predict which 
structure perfectly matches your needs. As said, you could use whatever 
you want. All you need to make sure is to finally translate to GIMPLE at 
some point.
> I look at the ghdl front end and I did not find vhdl-tree.def to see if they
> defined a new tree code for this fe.
>    
This file is not mandatory, I think. So, if they don't use one, they 
might not use additional tree codes. Well, if they use GENERC/tree-based 
IR at all!

Best regards,
Andi