[master] RFR: Load Klass* from header, C2 implementation [v4]

[Roman Kennke]

On Fri, 11 Feb 2022 07:11:40 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Revert unnecessary change
>>  - Experiment to keep using 8 as offset for LoadNKlass
>
> src/hotspot/share/opto/matcher.cpp line 2980:
> 
>> 2978:   }
>> 2979:   tty->print("--N: ");
>> 2980:   _leaf->dump(3);
> 
> Leftover debugging crumb?

The whole last change is intended for debugging with @rwestrel, I am not sure yet if we can convince C2 to work with 8 offset. We might revert back to offset 4 for all of C2.

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PR: https://git.openjdk.java.net/lilliput/pull/29