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

[Tobias Hartmann]

On Tue, 1 Jun 2021 10:21:20 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> src/hotspot/share/ci/ciInstanceKlass.hpp line 155:
>> 
>>> 153:   bool                   has_subklass()   {
>>> 154:     assert(is_loaded(), "must be loaded");
>>> 155:     if (_has_subklass == subklass_true) {
>> 
>> A comment explaining why we only cache `subklass_true` would be good. Also, do we still need a tri-state including `subklass_unknown`? It's now only used for initialization but not queried anywhere.
>
> Comment added.
> 
> Regarding `subclass_false` and `subklass_unknown`, keeping tri-state enum looks benign. Also, it makes sense to keep `subklass_unknown` to be able to distinguish between not yet initialized and already initialized cases (at least, during debugging).

Okay, looks good.

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