RFR: 8359394: Shenandoah: GC cause cleanup

[Aleksey Shipilev]

On Thu, 12 Jun 2025 23:42:41 GMT, William Kemper <wkemper at openjdk.org> wrote:

> We can remove `GCCause::_no_cause_specified` and need to add a case for `_shenandoah_humongous_allocation_failure` in `GCCause::to_string`. We are also missing `_shenandoah_humongous_allocation_failure` in the `SA` analog.

Shenandoah parts look good, but we should avoid changing shared code unnecessarily.

Changes requested by shade (Reviewer).

src/hotspot/share/gc/shared/gcCause.hpp line 58:

> 56:     /* implementation independent, but reserved for GC use */
> 57:     _no_gc,
> 58:     _no_cause_specified,

Code history shows this enum was there since the beginning of OpenJDK. So it is better to leave it alone. It is also less confusing to have only Shenandoah-specific changes in RFE that starts with "Shenandoah: ..."

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Changes requested by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25789#pullrequestreview-2924090662
PR Review: https://git.openjdk.org/jdk/pull/25789#pullrequestreview-2924091681
PR Review Comment: https://git.openjdk.org/jdk/pull/25789#discussion_r2144632935