[FFI] Mixed code in the JDK21 extension repo on Power

[ChengJin01]

I notice that https://github.com/ibmruntimes/openj9-openjdk-jdk21/tree/openj9/src/java.base/share/classes/jdk/internal/foreign/abi/ppc64 are currently merged with the Hostpot specific code intended for pLinux as follows:
/linux
ABIv2CallArranger.java
CallArranger.java
PPC64Architecture.java
TypeClass.java

which is wrong as these code are specific to the Hotspot implementation which doesn't belong the openj9 branch.

If we keep them there, it is easy to mess things up in compilation with such confusion.

FYI: @tajila, @pshipton

[ChengJin01]

@tajila & @keithc-ca,

I am considering to remove these Hotspot specific files/folders from https://github.com/ibmruntimes/openj9-openjdk-jdk21/tree/openj9/src/java.base/share/classes/jdk/internal/foreign/abi/ppc64 to avoid any issue on our side if you have no objection to this.

[keithc-ca]

In what way is the code specific to hotspot? I would expect the implementation to respect the ABI of the target platform which should be independent of any JVM implementation.

[ChengJin01]

Technically, we don't use any of these code there from OpenJ9 perspective as they are totally different in implementation. Keeping them there is misleading & easy to make mistakes in the future given our own code in the OpenJDK extension is only linked to our own FFI implementation.

[ChengJin01]

I also notice that https://github.com/ibmruntimes/openj9-openjdk-jdk21/blob/openj9/src/java.base/share/classes/jdk/internal/foreign/abi/ppc64/CallArranger.java has been changed to point to the FFI implementation in OpenJ9 when merging the latest master branch.

[ChengJin01]

As discussed with @keithc-ca offline, it is reasonable to keep these generic code in OpenJDK to avoid any conflicts from upstream, in which case I will need to figure out a way to keep both AIX and pLinux (from OpenJ9 perspective) work correctly with all unnecessary code removed.

[ChengJin01]

I will get back to work on this issue later after my vacation next week.

[ChengJin01]

With my solution at ChengJin01/openj9-openjdk-jdk21@9680612, it works good as expected on Power (AIX & pLinux) by verifying the FFI specific test suites in OpenJ9/Jtreg.

[ChengJin01]

Close this issue as all related PRs are merged to the repo.