Integrated: 8325671: Shenandoah: Introduce a ShenandoahGenerationType and templatize certain marking closures with it

[Y. Srinivas Ramakrishna]

On Mon, 12 Feb 2024 18:31:30 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

> 8325671: Shenandoah: Introduce a ShenandoahGenerationType and templatize certain marking closures with it

This pull request has now been integrated.

Changeset: f62f2adb
Author:    Y. Srinivas Ramakrishna <ysr at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/f62f2adbc3ec3cf8a9a59d3d766c60d11ebd77e2
Stats:     124 lines in 9 files changed: 71 ins; 3 del; 50 mod

8325671: Shenandoah: Introduce a ShenandoahGenerationType and templatize certain marking closures with it

In support of eventually supporting a generational version of Shenandoah, we introduce a ShenandoahGenerationType enum which currently has a single NON_GEN value for Shenandoah. The generational extension of Shenandoah will introduce additional enum values when GenShen is integrated. These will be used to specialize certain marking closures via templatization, such that suitable variations of the marking (and in the future other) closures can be used for the generational and non-generational variants of the collector while minimizing interference between the two variants while maximizing code-sharing without affecting correctness or performance.

This ticket introduces the new enum type and templatizes certain existing marking closures.

In effect, this should be semantically a no-op for current (non-generational) Shenandoah and ideally completely performance-neutral (to be established via measurements).

**Testing:**
- [x] jtreg hotspot_gc
- [x] github actions
- [ ] codepipeline perf & stress: in progress

**Performance:**
- [ ] specjbb w/shenandoah
- [ ] codepipeline perf: in progress

Reviewed-by: kdnilsen, shade

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PR: https://git.openjdk.org/jdk/pull/17815