[LLVMdev] [VMKit] 2.9 or ToT? Java version/features?

[Will Dietz]

Hi Nicolas,

Reviving old thread of sorts... thank you very much for your earlier
response--I apologize for not responding to tell you how very helpful
your information was!  Didn't come back because you gave me everything
I needed at the time :).

Anyway:

On Fri, May 13, 2011 at 2:00 PM, nicolas geoffray
<nicolas.geoffray at gmail.com> wrote:
> On Fri, May 13, 2011 at 7:30 PM, Will Dietz <willdtz at gmail.com> wrote:
> Today you can use both. I haven't improved vmkit much lately, so version 2.9
> and TOT are pretty much the same.

Looking at the vmkit-commits mailing list, seems like you've
changed/are changing a lot.

Is ToT generally stable enough for use in my projects, or should I
wait for a release?

>>
>> --What features of Java does VMKit support? Is there a corresponding
>> java 'version' (1.4, 1.6, etc) that VMKit supports? (Is this
>> documented somewhere? I was unable to find it)
>
> It implements the VM spec version 2 (+ some features of version 3 which is
> still unofficial). It uses  GNU Classpath for the base library, so the java
> version you're mentioning will be the one implemented in GNU Classpath, and
> that is 1.6 (with still some unimplemented feature of 1.6). But vmkit does
> not to have to be tight to a base library implementation. An interesting
> project to work on would be to support the OpenJDK library.

Supporting OpenJDK is very interesting indeed, as full 1.6 support is
important to us.  How intense of a project would undertaking this be?
And is this something you could semi-mentor on if I were to undertake
it? :).
Not sure if we'll go in this direction, but if we are to continue to
use VMKit I think we'll have to do so.

>>
>> And since I'm feeling lucky: What's the status of VMKit? Is it still
>> able to run tomcat, and the dacapo benchmarks (on x86 anyway)?
>>
>
> Yes, it works well on a x86 machine (x64 is not supported by the GC). And it
> is able to run tomcat and some of the dacapo benchmarks. There are some
> applications and dacapo benchmarks that don't work because of GNU Classpath
> being incomplete. Another reason to try to support the OpenJDK library
>>

Agreed, understood, and great news.  Especially if using OpenJDK isn't
an impossible undertaking :).

Regarding the lack of 64bit support, are there GC's that support 64bit
that might be worth looking into?

Technically I'm not sure we need a 64bit JVM, but our tools are 64bit
and would be ideally be integrated into the runtime...

That brings me to my last question, a new one!

Is it still possible to AOT code?  I'm planning on doing (potentially
rather expensive) static analysis on the IR form of Java code, as well
as being worried about performance issues with using a JIT (especially
since the LLVM JIT AFAIK doesn't do any kind of adaptive
optimizations, etc, seems static compilation should always result in
faster code...).

Any thoughts you can share on that (there's a precompiler now, is that
a partial AOT?) would be greatly appreciated.

>> Thanks for your time,

Let me take this opportunity to re-thank you for your efforts and any
insights you can offer.

Thanks, and have a good one!

~Will