Open sourcing JDK 9 ARM ports

[Andrew Haley]

On 23/08/16 15:00, Bob Vandette wrote:
> As the Java SE Mobile and Embedded Lead at Oracle, I'm pleased 
> to be able to let you know about Oracle's plans to open source 
> its Linux ARM 32 and 64 bit ports of Oracle Java SE for JDK 9 
> in the OpenJDK Community.

With my "community representative on the Governing Board" hat on:

Of course I welcome this announcement.  I've been pressing for more of
Oracle's software to be open sourced for many years, so of course I
can't complain when it happens.

With my "OpenJDK project lead" hat on:

However, there are going to be substantial practical problems handling
this donation.  The OpenJDK AArch64 port is well-established, performs
well, and is ready for release as part of OpenJDK 9.  I don't expect
that to change significantly: the OpenJDK 9 tree is stabilizing for
release, and we're past Feature Complete.  On the other hand, the
AArch32 port is very new, and the C1 interpreter is just about to be
contributed by Azul.  (If I were Azul I'd be very irritated by this
news after they've put in a lot of work, but I'll leave any more
comments about that to them.)

I do not believe that it makes any sense in the long term (or the
medium term) to have two active ports to the same architecture in the
OpenJDK source tree.  It would significantly dilute community effort,
and it would be extremely unhealthy to have two groups competing with
each other.  And there are other issues: for example, which would be
the default port to build?  Fracturing the ARM OpenJDK community would
be a disaster.

So, we can decide to adopt one port or another wholesale for the
future or we can try to merge the best bits.  Merging would probably
be a big effort, and I'm not sure we have the people we'd need to do
it.

> In addition, our implementation provides the ability to build 
> Linux ARM interpreter runtimes statically for platforms that 
> do not support dynamic code generation.

That's a nice feature.

> There are a few potential challenges ahead if you all agree that it's 
> a good idea to contribute our implementation to the Aarch32 project.
> 
>   1. Our code provides both a 32-bit and a 64-bit implementation.
>   2. Currently there are no Oracle Commiters/Reviewers in this Project. 

Ah.

>   3. Our development is focused solely on JDK 9 rather than JDK 8.
> 
> I look forward to your feedback on how to best move ahead.

Please create a source tree in the Aarch32 project and commit all the
code to that.  When we can all see the code we'll be in a much better
position to think about what to do next.

Thanks,

Andrew.