RFR: JDK-8314777: GenShen: Alias young and old marking bits to legacy Shenandoah marking bit in gc state [v6]

[William Kemper]

On Thu, 24 Aug 2023 21:25:38 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This change sets the MARKING bit of _gc_state whenever either Young marking or Old marking is active.  With this change, barrier code more closely resembles the code in the original single-generation Shenandoah.  The performance impact is negligible.  The primary benefit is to simplify code reviews and clarify that the addition of generational mode to Shenandoah does not negatively impact performance of single-generation Shenandoah.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove over-zealous assertion

Marked as reviewed by wkemper (Committer).

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PR Review: https://git.openjdk.org/shenandoah/pull/309#pullrequestreview-1596231692