RFR: 8234502: Merge GenCollectedHeap and SerialHeap [v5]

[Albert Mingkun Yang]

On Fri, 8 Dec 2023 13:01:55 GMT, Lei Zaakjyu <duke at openjdk.org> wrote:

>> 8234502: Merge GenCollectedHeap and SerialHeap
>
> Lei Zaakjyu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   resolve conflict

As you pointed it out previously, some files in `src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/` need to changed (before or inside this PR). The bottom line is that `GenCollectedHeap` should not exist in the codebase after this PR.

src/hotspot/share/gc/shared/space.cpp line 131:

> 129: #if INCLUDE_SERIALGC
> 130:       cp->gen = SerialHeap::heap()->young_gen();
> 131: #endif // INCLUDE_SERIALGC

This doesn't look right. `INCLUDE_SERIALGC` and its counterparts in other GCs are to support release builds without certain GCs. IOW, when this is `false`, it should still build. I believe https://github.com/openjdk/jdk/pull/16842 should make this part of change obsolete.

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PR Review: https://git.openjdk.org/jdk/pull/16927#pullrequestreview-1772359002
PR Review Comment: https://git.openjdk.org/jdk/pull/16927#discussion_r1420454416