AArch64 in JDK 9?

[Andrew Haley]

Hi,

On 04/17/2014 11:16 AM, Volker Simonis wrote:
> 
> I'd highly welcome your port in the main HotSpot tree!
> 
> Unfortunately I'm not the decision maker here, but I can try to
> outline the steps we took to bring in our port and cc some people
> (Iris, Azeem) who may know how to help.
> 
> - First of all we were told to and finally filed a JEP for the
> integration project (in our case it was JEP 175: PowerPC/AIX Port -
> http://openjdk.java.net/jeps/175). I think the main reason why this is
> necessary is that such a project requires a certain amount of help
> from Oracle and in order to get that you'll need to get your project
> sponsored and funded. This all is formalized trough the JEP process.

OK.

> - You'll probably need to have a "staging" repository as a mirror of
> the current jdk9-dev forest. The staging repository will be kept in
> sync with its mirror and additionally collect all your porting changes
> as valid (i.e. in the sense of 'jcheck') and reviewed OpenJDK
> changesets.

Sure, I was planning to do that anyway.  There is one thing I don't
understand how to do, though.  jcheck wants bug IDs for all changes,
right?  So does that mean that you have to create bug IDs when you
create the staging repository?

> Once your port is completed in the staging repository, Oracle will
> probably want to do some bigger testing on it before the complete
> port will be bulk integrated into the main repositories.  Notice
> that we actually had two staging repositories, one for jdk8 and one
> for jdk9. I'd suggest you start with jdk9 and once you're finished
> with that and depending on your wishes, you may also do the same
> with jdk8u. But notice that Oracle is not following the HotSpot
> Express model any more. This means that downporting your AArch64
> port to jdk8u will get continuously harder over time, even if you
> manage to get into the main jdk9 repositories.
> 
> - After we got the our JEP approved and funded, we created a detailed
> "Integration Plan" in the OpenJDK Wiki (see
> https://wiki.openjdk.java.net/pages/viewpage.action?pageId=13729959)
> where we outlined the different integration steps in some more detail.
> I assume that you mainly only have HotSpot changes, so in one sense
> your integration plan will be simpler. On the other hand, bringing in
> HotSpot changes is the more intricate part of a port integration
> because you can not check in changes yourself, even if you are a
> committer, because of the known infrastructure problems (i.e. the need
> to run all the changes trough the Oracle-internal JPRT test system).

Right.

> There's also the problem that Oracle maintains some closed
> repositories (e.g. their ppc ar arm ports) in parallel to the
> OpenJDK repositories and changes in shared code may require
> modifications in their closed ports. Therefore most changes to the
> "staging" repository will have to be done by Oracle folks who can
> take care of their proprietary port as well.

Sure, I get that.  I'll have to go over our code changes to see if
anything affects non-AArch64 ports.

> I'd therefore wait with the creation of a new repository as you
> suggested until you synchronised with some of the Oracle folks. You
> really need to find some good friends in the HotSpot group to get this
> project done:)

Well, yes.  And this is going to get more common, I hope, so we need
to establish a smooth pathway to help people get ports in.

One interesting challenge here is that there really isn't much AArch64
hardware around for other people to test on, but I hope that it will
be common enough later in the year.

> If you have any questions or if there's anything I can do please don't
> hesitate to let me know.

OK, I'll remember that.

Thanks,
Andrew.