RFR: 8298601: Refactor archiving of java.lang.Module objects [v3]

[Coleen Phillimore]

On Tue, 3 Jan 2023 20:07:05 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> This RFE is a prerequisite for [JDK-8296344: Remove dependency on G1 for writing the CDS archive heap](https://bugs.openjdk.org/browse/JDK-8296344). 
>> 
>> The main change of this RFE is in `HeapShared::archive_reachable_objects_from()`. We avoid the use of "archived objects" in the interface between CDS and the module system, and use integer "root indices" instead. (See note [1] in [JDK-8298600](https://bugs.openjdk.org/browse/JDK-8298600).)
>> 
>> Also, for better encapsulation, the module-specific code has been moved from `HeapShared::check_module_oop()` to the three new functions in modules.cpp.
>> 
>> ----
>> 
>> Besides the refactoring, this RFE also tightens up the code that deals with `java.lang.Module` oops and the corresponding C++ `ModuleEntry` objects.
>> 
>> As this is admittedly an obscured area of the CDS archive heap, I've added the following:
>> 
>> - Assertions to make sure that when an oop is archived, the corresponding C++ object is also archived, and vice-versa.
>> - More comments
>
> Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge branch 'master' into 8298601-refactor-archiving-of-java-lang-Module-oops
>  - review from @coleenp and @calvinccheung
>  - 8298601: Refactor archiving of java.lang.Module objects

Looks good.

-------------

Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11715