[lworld] RFR: 8375434: [lworld] Add comment for null-check in InlineKlass::read_payload_from_addr

[Joel Sikström]

On Thu, 15 Jan 2026 15:03:29 GMT, Frederic Parain <fparain at openjdk.org> wrote:

>> Hello,
>> 
>> Update: There is nothing wrong with the logic. I added a comment to clarify why the second null-marker check is needed. Thanks.
>> 
>> ~~Right now we check the null-marker for the NULLABLE_ATOMIC_FLAT LayoutKind twice, both before and after allocating a heap instance. The first check returns nullptr early if the null-marker is set, as we don't have to allocate an object on the heap if we are going to return nullptr anyways. The other check is redundant, since if the null-marker is not set, the source object is non-null, which means the destination (res) object is non-null as well after copying, so the code inside it is unreachable.~~
>> 
>> Testing:
>> * Oracle's tier1-4, hotspot_valhalla, jdk_valhalla
>> * ~~I also added a `gurantee` for the removed code and ran through hotspot_valhalla and jdk_valhalla locally.~~
>
> Adding a comment to explain the rational of the second null-marker check is a good idea.

Thank you for the reviews @fparain @Arraying!

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PR Comment: https://git.openjdk.org/valhalla/pull/1914#issuecomment-3767189673