[lworld] RFR: 8376135: [lworld] Add JIT support for NULLABLE_NON_ATOMIC_FLAT layout [v4]

[Quan Anh Mai]

On Tue, 27 Jan 2026 09:37:41 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This PR implements the support of `NULLABLE_NON_ATOMIC_FLAT` layout in the JITs. There is nothing to do in C2. In C1, I need to implement loading/storing nullable value of a non-atomic field.
>> 
>> The test `TestValueClasses` is failing with `-XX:-TieredCompilation`, which I suspect is due to the substitutability test handling padding bytes incorrectly.
>> 
>> Please kindly review what there are for now, thanks a lot.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove unused variable

test/hotspot/jtreg/runtime/valhalla/inlinetypes/FlatArraysTest.java line 474:

> 472:   }
> 473: 
> 474:   static value class FieldsHolder {

I don't see why this class needs to be `value`, and making it `value` allows `nav` to be a `NULLABLE_NON_ATOMIC`, to which there is no corresponding array.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1970#discussion_r2731105952