RFR: 8256072: Eliminate JVMTI tagmap rehashing [v4]

[Kim Barrett]

On Thu, 3 Nov 2022 12:46:00 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 incrementally with one additional commit since the last revision:
> 
>   Fix has_no_hash into fast_no_hash_check().

Good thing Erik caught the displaced markword issue.  Looks even better now.

src/hotspot/share/oops/oop.hpp line 294:

> 292: 
> 293:   // identity hash; returns the identity hash key (computes it if necessary)
> 294:   inline bool fast_no_hash_check();

Seems like `fast_no_hash_check` ought to be later in this grouping.  The preceding comment is about `identity_hash`.

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Marked as reviewed by kbarrett (Reviewer).

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