[Mono-list] Announce: A .NET assembly -> native code generation tool (ala ngen for MONO)

Dietmar Maurer dietmar@ximian.com
29 Jul 2002 11:08:17 +0200

On Sun, 2002-07-28 at 06:03, Miguel de Icaza wrote: 
> Hello Zoltan,
> >    The first version of my ngen clone for MONO is available at:
> > 
> > http://www.nexus.hu/vargaz2
> This announcement is of course really exciting.  I have only taken a
> very superficial look so far at the code generator, but the approach is
> a very interesting idea.  I will let Dietmar and Paolo comment further
> on it.
wow, about 6000 LOC! I have not looked into every detail, but i think
this approach has some problems: 

        1. It does not work with exceptions: The current code is
           incorrect because it does not save/restore the LMF when
           calling precompiled methods - but saving/restoring the LMF
           would lead to serious performance problems.
        2. Array bound checking: There is no array bound checking at the
           moment and maybe that is the only reason why it speeds up
           pnetmark? gcc is unable to do bound check removal, so array
           access will be slow (or you have to remove that checks before
           you emit C code).
        3. I wonder if gcc is really able to optimize the emitted C#
           very much.
> What I wanted to look into was to use the JIT to generate code that
> would end up in a library, basically reusing the JIT, but turning on all
> the optimizations for this.
This approach would also avoid much code duplication. 

So IMO we should first check if we gain anything by using gcc, and of
course we need a solution for the exception problem? 

- Dietmar