RFR: 8338658: New Object to ObjectMonitor mapping: s390x implementation [v2]

[Lutz Schmidt]

On Wed, 4 Sep 2024 12:39:52 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

>> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   review comments
>
> src/hotspot/cpu/s390/macroAssembler_s390.cpp line 6030:
> 
>> 6028:       z_lghi(top, 0); // tmp1 is free at this point
>> 6029:       z_stg(top, om_cache_addr);
>> 6030:     }
> 
> @RealLucy should I remove the else Part ? I tested on tier1 and it is not being executed, So maybe safe to remove ?

I am often undecided myself. The code as it is now is correct for all displacements. If you omit the else part, you introduce a hidden dependency on the layout of BasicObjectLock and BasicLock. On the other hand, how likely is it that anybody will fundamentally change the layout and thus break the disp12 requirement? Compact or generally valid? **Your choice.**

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PR Review Comment: https://git.openjdk.org/jdk/pull/20740#discussion_r1743759824