[LLVMdev] gcc, conceptgcc, and llvm-gcc

[Duncan Sands]

Hi Xiaolong,

> My previous work was done mainly in the front-end of conceptgcc,
> whereas recently I am doing some code analysis in the middle-end of
> llvm. I am considering to port my previous work to llvm.
>
> So, I am very concerned with the difference between gcc and llvm-gcc,
> and of course the difference between gcc and conceptgcc. I have no
> idea of the former difference, though I have some idea of the latter
> difference.

I don't think llvm-gcc is interesting for you.  I think you would do better
to work on the clang front-end.  It seems to me that llvm-gcc is being
abandoned, and everyone is migrating either to clang (for C/C++/ObjC) or
dragonegg (for Fortran/Ada etc).

> Would someone briefly please point out the changes of llvm-gcc
> relative to gcc? Hopefully, with your input, I could evaluate the
> efforts when I patch a normal gcc with the differences between gcc and
> llvm-gcc :)

The differences are big, and you will feel a lot of pain if you try to
apply them to a gcc more recent than gcc-4.2.  On the other hand, the
dragonegg project (http://http://dragonegg.llvm.org/) already ported
llvm-gcc to gcc-4.5, and while it still requires patching gcc, the patch
is tiny and trivial.

Ciao,

Duncan.