RFR: Make immediate trash of old regions with no live objects

Mon Aug 16 16:36:58 UTC 2021

On Mon, 16 Aug 2021 15:15:10 GMT, William Kemper <wkemper at openjdk.org> wrote:

> At the end of old marking we can immediately recycle regions with no live objects. This optimization is already done for young/global collects, but it was missing from old collections. This fixes an assertion during preparation for evacuation that _all_ cset regions have _some_ live data.

Looks good! Thanks!

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Marked as reviewed by rkennke (Lead).

PR: https://git.openjdk.java.net/shenandoah/pull/57