[lworld] RFR: 8331006: [lworld] Support of null markers for nullable flat fields [v2]

[Dan Heidinga]

On Tue, 30 Apr 2024 14:12:04 GMT, Dan Heidinga <heidinga at openjdk.org> wrote:

>> Frederic Parain has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fixing issues spotted during reviews
>
> src/hotspot/share/interpreter/interpreterRuntime.cpp line 362:
> 
>> 360:     // The interpreter copies values with a bulk operation
>> 361:     // To avoid accidently setting the null marker to "null" during
>> 362:     // the copying, the null marker is set to non zero in the source object
> 
> Is this saying if the null marker is embedded in the value field layout rather than placed separately, we set it to non-null before writing it into the container?  This tripped me up a little bit reading the code but I think it makes sense

How does that work for our memory barriers then?  Do we not need a release here as well given the acquire used to read the null marker?

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1078#discussion_r1584906915