[lworld] RFR: 8281116: [lworld] Adding Preload attribute support

[Frederic Parain]

On Wed, 2 Feb 2022 14:11:27 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

>> Please review this changeset adding support for the Preload attribute.
>> It includes a logging feature to track and diagnose those optimistic class loading.
>> 
>> Tested with Mach5 tier1.
>> 
>> Thank you,
>> 
>> Fred
>
> src/hotspot/share/oops/instanceKlass.hpp line 291:
> 
>> 289:     _misc_has_preload_attribute               = 1 << 23  // class has a Preload attribute
>> 290:   };
>> 291: 
> 
> Is the _misc_has_preload_attribute flag needed, or can the code just check if _preload_classes equals Null?

Strictly speaking, it is not needed. At some point, I've considered putting the _preload_classes pointer into the optional part of InstanceKlass, which would have required this flag. But finally it is declared as a regular field, so this flag can be removed.

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PR: https://git.openjdk.java.net/valhalla/pull/623