Re: New GCC Runtime Library Exception

[Chris Lattner <clattner at apple dot com>]

On Jan 29, 2009, at 7:38 AM, Joern Rennecke wrote:

> > > The difference is that the front end does not work on source  
> > code, but
> > > Java bytecode, which seems closer to intermediate representation  
> > than
> > > to a "high-level, non-intermediate language".
> >
> > I think it is clear that Java bytecode, which can even be executed
> > directly by some microprocessors, is not a "compiler intermediate
> > representation."
>
> That is beside the point.  It is not a high level language.  Hence,
> when you use gcc to compile Java bytecode to Target Code, this is not
> an eligible compilation process.
>
> When you use a non-GPL-compatible java frontend to compile Java  
> source to
> bytecode and then use GCC to compile this to Target Code, it is not
> an eligble compilation process either, because you used a non-GPL- 
> compatible
> frontend.

This issue is also somewhat confusing to me.  It is a moot point,  
because LLVM is GPL compatible, but is LLVM .ll language considered a  
target code, intermediate representation, or a "high-level, non- 
intermediate language"?  It is not clear to me how LLVM .ll files are  
different from .c files that are used as intermediates between bison  
and a C compiler.

LLVM .ll files are a fully documented language and people write them  
by hand all the time.  It is quite arguably much higher level that  
machine code (having concepts like "call with arguments", a type  
system, etc), and is fully specified (http://llvm.org/docs/ 
LangRef.html).  It seems quite possible to argue that it is a "high- 
level, non-intermediate language" (at least at least as much as C is).

Is the wording intended to allow LLVM .ll files as "high-level, non- 
intermediate language", or are they considered an IR?  What is the  
dividing line?  It seems that this is a very important issue for the  
entire license.

-Chris