RFR: 8256072: Eliminate JVMTI tagmap rehashing [v2]

Wed Nov 2 20:55:26 UTC 2022

On Wed, 2 Nov 2022 20:44:58 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Use identity_hash for objects in the JVMTI TagMap table.  If the object has no hashcode, it's not in the table.
>> Tested with tier1-6.
>
> Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' into jvmti
>  - 8256072: Eliminate JVMTI tagmap rehashing

Looks good.  Yay code deletion!

I was particularly happy to see `set_needs_rehashing` removed from all the GCs.

As a followup, I think `CollectedHeap::hash_code` is unused after this change.

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Marked as reviewed by kbarrett (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10938