Question on "JEP: JVMCI based JIT Compiler pre-compiled as shared library"

[Vladimir Kozlov]

Hi Andrew,

On 11/28/19 7:40 AM, Andrew Dinn wrote:
> Hi Vladimir,
> 
> On 22/11/2019 18:23, Vladimir Kozlov wrote:
> <snip>
>> As you remember during this JVMLS we talked about our plan to transition
>> to Graal from C2 in a future. And using AOT'ed (SVM'ed) Graal (libgraal)
>> is important part of this transition, 8220623 is part of that. Most work
>> is done by GraalVM group in Oracle. They just released 19.3 version of
>> GraalVM that is based on JDK 11 and using libgraal by default which use
>> JVMCI changes from 8220623.
> 
> I am not sure that last statement is 100% correct :-)

My point was that 8220623 JVMCI changes are used by GraalVM (regardless what is used as base).

> 
> It depends what you mean by 'based' on jdk11. The latest GraalVM relies
> on a specific downstream jdk11 tree maintained by Oracle. GraalVM users
> have to download a build derived from that tree in order to be able to
> use the Graal JIT and Substrate native image generator to build native
> images and shared libraries including, I believe, libgraal. I understand
> that the changes made to that downstream repo are public i.e. Oracle's
> GraalVM team have published sources for this tree which include the
> relevant backports of upstream patches.

Some changes pushed into GraalVM open repo are different from what was pushed into private Oracle JDK 11u. The sum of 
changes should be the same but I can't guarantee it because we (in HotSpot group) only fully tested Oracle JDK 11u.

> 
> Red Hat as maintainers of jdk11u would very much like to correct that
> situation (as, I believe, would the GraalVM team). We have a list of all
> the JIRAs whose patches have been backported. Is there any reason you
> are aware of for the jdk11u maintainers not to backport the relevant
> patches from the jdk dev tree to jdk11u?

It is up to you. But it may help that a code in Open and Oracle JDK 11u is in sync.
The main reason we backported these changes is to help GraalVM release to avoid building their own JDK 11u.

> 
>> On OpenJDK side we plan to release libgraal EA based on Metropolis
>> repository, as I said during JVMLS. This is tracked by RFE [1]. RFE's
>> description is outdated since Metropolis repo is based on JDK 14 now and
>> I need to update it. There is also Graal's PR, Bob V. is working on, to
>> adjust upstream Graal/SVM code to API changes done in JDK 14.
> 
> That's very good news. I'm very much looking forward to seeing
> Metropolis acquire both a JIT and a VM implemented in Java.

Thanks,
Vladimir

> 
> regards,
> 
> 
> Andrew Dinn
> -----------
>