RFR: 8309874: NMethod barriers may remain armed when regions are promoted in place

[William Kemper]

On Wed, 14 Jun 2023 20:30:03 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Genshen runs in-place promotions during the evacuation phase. If the cycle is _only_ performing in-place promotions, it should not arm NMethod barriers. The barriers are now only armed and disarmed if the collection set is not empty.

This addresses an assert on our 17 branches, but I suspect it is a performance improvement as well.

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PR Comment: https://git.openjdk.org/shenandoah/pull/286#issuecomment-1592092517