RFR: 8314329: AgeTable: add is_clear() & allocation spec, and relax assert to allow use of 0-index slot [v2]

[Albert Mingkun Yang]

On Fri, 19 Jan 2024 00:19:36 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> I'd like to propose the following changes to the AgeTable (motivated by the uses in generational shenandoah):
>
> Y. Srinivas Ramakrishna has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Code review from earthling-amzn: Early return.

src/hotspot/share/gc/shared/ageTable.hpp line 57:

> 55:   void clear();
> 56:   // check whether it's clear
> 57:   bool is_clear() PRODUCT_RETURN0;

The name seems a "proper" API; why is it only for non-product? Is it because it's for verification only? What's its (intended) use case?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17470#discussion_r1458902589