RFR: 8325808: GenShen: Move generational mode code out of shFullGC.cpp

[Y. Srinivas Ramakrishna]

On Mon, 19 Feb 2024 18:26:45 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> This change reduces the differences from the upstream branch by moving large chunks of generational mode code into separate files.
>
> src/hotspot/share/gc/shenandoah/shenandoahGenerationalFullGC.hpp line 49:
> 
>> 47: };
>> 48: 
>> 49: class ShenandoahPrepareForGenerationalCompactionObjectClosure : public ObjectClosure {
> 
> See comment in `ShenandoahPrepareForCompactionTask::prepare_for_compaction()`. I think this closure should include `prepare_for_compaction` in its public API, and full gc should just invoke that method of the closure directly.
> 
> If this simplification works out, then it would also affect the sister upstream PR https://github.com/openjdk/jdk/pull/17894 similarly.

Left a link there as well: https://github.com/openjdk/jdk/pull/17894#discussion_r1494924914

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/398#discussion_r1494929290