RFR: 8270333: -XX:+VerifyStringTableAtExit should not do linear search [v4]

[Yumin Qi]

On Wed, 14 Jul 2021 16:45:49 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> The implementation of `-XX:+VerifyStringTableAtExit` used a linear search to check for duplicated strings in the interned string table. This would be excessively slow if there were more than a few thousand strings.
>> 
>> This PR uses a hashtable so we can avoid doing a linear search. The table is sized such that each bucket has 8 items on average.
>> 
>> Since this code is executed only for verification, I added a new `java_lang_String::hash_code_noupdate(oop)` function, so we can avoid causing side effects.
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   @yminqi comments

LGTM.

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Marked as reviewed by minqi (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4772