RE: GCJ as cross-compiler to embedded system

[Gustav Kälvesten <gustav dot kalvesten at axis dot com>]

Hi Tom,

> Gustav> We are looking into bringing a JavaVM to our embedded systems
> Gustav> platform (eCos as OS and ETRAX processor). We are currently
> Gustav> using 'gcc' as cross-compiler for our development work.  A
> Gustav> question that has arisen is if it is possible to use 'gcj' to
> Gustav> compile the class libraries of the JavaVM into native code?
> Gustav> This should improve the speed drastically, right?  Anyone who
> Gustav> has done this and has any input on the difficulties and
> Gustav> performance improvement?
> 
> When you say "class libraries of the JavaVM", what do you mean?
> gcj can compile a lot of Java code.  However, you can't really use it
> to compile the base libraries.  You have to use the base libraries
> which come with it.

What we was thinking was to compile the base classes of the Sun J2ME CVM
and its CDC-Foundation packages to native code with gcj. Isn't that possible? 
Perhaps I'm using the wrong terms. Perhaps better to say that we plan to use gcc with the Java front-end.
 
> In the past we've had libgcj running on eCos.  This port has
> bit-rotted a bit, but it should be possible to resurrect it.

I don't think there is a need for libgcj in our case? 
Is the eCos port available somewhere?

> gcj can improve performance, but I believe the current state is that
> it is about equivalent to the current generation of JITs.  On the
> other hand, in an embedded context it may be more attractive because
> JITs memory in which to compile code, whereas gcj does not.
> 
> As always, which approach is best is highly dependent on the
> constraints under which you operate.

As the Sun CVM currently doesn't include a JIT we don't have such an option.
And as you say, we have quite limited memory resources unfortunately.

- Gustav