RFR: 8262046: Clean up parallel class loading code and comments [v2]

[Coleen Phillimore]

On Tue, 30 Mar 2021 10:14:35 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix some comments and add placeholder CCE logging.
>
> src/hotspot/share/classfile/systemDictionary.cpp line 383:
> 
>> 381: // the super class directly, then resume steps 4-6.
>> 382: //
>> 383: //
> 
> resolve_super_or_fail had this comment that I found difficult to understand and work through, which I did at one point, so I wanted to replace it with one that seemed less so.  It occurs to me that this is probably unhelpful also.   Maybe the whole comment from lines 351 to 381 should be replaced with a sentence like:
> 
> //resolve_super_or_fail adds a LOAD_SUPER placeholder to the placeholder table before calling
> // resolve_instance_class_or_null.  ClassCircularityError is detected when a LOAD_SUPER or LOAD_INSTANCE
> // placeholder for the same thread, class, classloader is found.
> 
> I'm unlikely to work through the new comment example again myself.

Since nobody wants to read this example in this comment and neither do I, I'm removing it.  Debugging this using -Xlog:class+load+placeholders=debug will show the stacking of placeholders that detect CCE.

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PR: https://git.openjdk.java.net/jdk/pull/3200