[cfe-dev] Tree transformation in clang

[Vassil Vassilev]

Hi,
   TreeTransform is part of the "curiously recurring template pattern" 
used all around in clang.
You could define your own transformation that uses that pattern. It is 
very efficient because it
allows to have sort-of inheritance without having vtables.
Example code you can find in:
/lib/Sema/SemaTemplateInstantiate.cpp
/lib/Sema/SemaTemplateDeduction.cpp
/lib/Sema/SemaTemplate.cpp
However, TreeTransform is not public interface...

There were a lot of changes in it recently and maybe my experience is 
old-dated but
I tried to use it once and I had hard time when I wanted to replace one 
node with 2 or more
nodes or when I tried to remove nodes. For 1:1 transformation I think is 
very good interface, though.

Talking about optimizations: Have you consider the LLVM bitcode - it is 
SSA based and IMHO
is much more suitable for optimizations?

Vassil

On 12/01/2011 02:36 PM, eyasu getahun wrote:
>
> Hello Vasil,
>
> Thanks for your detail explanation. The main thing what I want to do 
> is AST level optimization. But before implementing optimizations, I 
> need to transform the resulting AST which is build by clang after 
> parsing the given source code. That mean i want to transform this AST 
> to another AST. Later it will be easy to implement optimizations on 
> the new AST. When i read clang source files, I got 
> TreeTransformation.h file. I thought that there is tree to tree 
> transformation that is already implemented inside clang. But I 
> couldn't get the implementation. Now am getting information from you 
> guys that this file is just a facility or base for implementation 
> other transformations. So, this is good information that I got from 
> you guys. Now am going to do the transformation by my self and 
> implementing optimizations later on. If there was implemented tree to 
> tree transformation, i don't need to go implement tree transformation.
>
> Hope you got my idea. It is just my ideal design and didn't go 
> further. I will start the tasks soon. Do you have any idea or 
> suggestion how to go? Thanks again.
>
> On Thu, Dec 1, 2011 at 9:01 PM, Vassil Vassilev 
> <vasil.georgiev.vasilev at cern.ch 
> <mailto:vasil.georgiev.vasilev at cern.ch>> wrote:
>
>     Hi,
>       TreeTransform is the facility used to rebuild the templated
>     nodes of the AST once
>     clang has the full type/value information (for example at
>     instantiation time). It replaces
>     the nodes that are marked as of dependent type with their actual
>     instantiation type and
>     performs the semantic checks with the new types.
>
>       Maybe if you clarify a little bit more (and perhaps give
>     examples) I can be more helpful.
>     In general TreeTransform is not meant to implement every possible
>     tree-to-tree transformation.
>
>     Nevertheless, it can be used as model how to build your own one.
>     Right now I am not aware of
>     an interface that implements arbitrary tree-to-tree transformation.
>     However, there are couple of interfaces that you might find useful
>     for that. You might want to
>     have a look at clang::ASTConsumer, clang::SemaConsumer and
>     clang::RecursiveASTVisitor
>
>     Depending on what is the exact idea of the transformation you
>     could also use clang's
>     rewrite subsystem, which is pretty powerful, but it AFAIK it
>     doesn't work on AST level. It is more
>     source-to-source transformation.
>
>     Vassil
>
>
>     On 11/30/2011 04:20 AM, eyasu getahun wrote:
>>     Hello all,
>>
>>      I have seen tree transformation in clang(TreeTransform.h). This
>>     is to transform one AST to another AST. But it is not clear for
>>     me how they used this header file for the transformation. I
>>     didn't see the function for the transformation. Just they used
>>     this header file for semantic template instantiation and template
>>     deduction. Even there is no explicit command line option for the
>>     transformation. Do you guys think that the transformation is well
>>     implemented and documented? please let me know if you have any
>>     idea about the transformation that they used in clang. Thanks in
>>     advance!
>>
>>
>>     -- 
>>     *With Best Regards,
>>
>>     ===========================================
>>     Eyasu Getahun*
>>
>>
>>
>>     _______________________________________________
>>     cfe-dev mailing list
>>     cfe-dev at cs.uiuc.edu  <mailto:cfe-dev at cs.uiuc.edu>
>>     http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>
>
>
> -- 
> *With Best Regards,
>
> ===========================================
> Eyasu Getahun*
>
> 1 Fusionopolis way, #08-10 Connexis North Tower
> Singapore 138632, Singapore
> Mobile: +393279239907
> *===========================================
> *

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20111201/56d0d91c/attachment.html>