RFR: 8297914: Remove java_lang_Class::process_archived_mirror() [v3]

[Calvin Cheung]

On Fri, 13 Jan 2023 19:00:40 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> This is another prerequisite for [JDK-8296344](https://bugs.openjdk.org/browse/JDK-8296344).
>> 
>> Before this PR, when archiving mirror objects (i.e., instances of `java.lang.Class`):
>> - We first allocate a copy of the mirror inside a safepoint. 
>> - We then reinitialize the contents of the copy to the desired state (so that it can be used by `Klass::restore_unshareable_info()`
>> 
>> This copy-and-modify operation inside the safepoint makes it difficult to implement [JDK-8296344](https://bugs.openjdk.org/browse/JDK-8296344). It violates the requirements [1] and [2] as stated in [JDK-8298600](https://bugs.openjdk.org/browse/JDK-8298600). Also, the reinitialization code is complicated.
>> 
>> After this PR:
>> - During the creation of each regular mirror object, we allocate a "scratch mirror" object, which has the states as expected by `Klass::restore_unshareable_info()`. See `java_lang_Class::create_scratch_mirror()`.
>> - When the archive heap is dumped inside a safepoint, we use the scratch mirror, so we can avoid the copy-and-modify operation. See `HeapShared::archive_java_mirrors()`.
>> 
>> Testing: tiers 1-4
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   @calvinccheung comment - removed unnecessary ObjArrayKlass::deallocate_contents

Thanks for the update.

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Marked as reviewed by ccheung (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11853