RFR: 8267947: CI: Preserve consistency between has_subklass() and is_subclass_of() [v2]

[Vladimir Ivanov]

On Tue, 1 Jun 2021 10:24:37 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> CI caches `Klass::subklass() != NULL` query, but concurrent class loading can
>> invalidate the cached value. Though recorded dependency won't let the nmethod
>> to be installed, the inconcistency can manifest as type paradoxes until
>> compilation is finished. 
>> 
>> The fix caches only `true` value (since it can't change unless class unloading
>> takes place) and queries the VM otherwise.
>> 
>> Testing:
>> - [x] hs-tier1 - hs-tier6
>
> Vladimir Ivanov has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Refactor asserts
>  - Improve comment

Thanks for the reviews, Tobias and Roland.

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PR: https://git.openjdk.java.net/jdk/pull/4269