[master] RFR: Read class from object header [v3]

[Roman Kennke]

On Fri, 30 Jul 2021 07:55:31 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add missing new markWord.inline.hpp
>
> src/hotspot/share/gc/shared/preservedMarks.inline.hpp line 58:
> 
>> 56:     header = header.displaced_mark_helper();
>> 57:   }
>> 58:   narrowKlass nklass = header.narrow_klass();
> 
> This assumes `UseCompressedClassPointers` is `true`, right? Needs to be asserted?

Yes, the whole Lilliput assumes UseCompressedClassPointers==true. We enforce that in arguments.cpp. We might even go so far to remove the flag and code paths altogether, but not now.

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PR: https://git.openjdk.java.net/lilliput/pull/12