[lworld] RFR: 8376135: [lworld] Add JIT support for NULLABLE_NON_ATOMIC_FLAT layout [v8]

[Quan Anh Mai]

On Sat, 31 Jan 2026 06:09:12 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:
> 
>  - Merge branch 'lworld' into nullablenonstatic
>  - Remove Strict
>  - Merge branch 'lworld' into nullablenonstatic
>  - Adjust test, add comments and examples
>  - add assert
>  - remove unused variable
>  - no_null_marker
>  - rename null_free in InlineTypeNode::initialize_fields to has_null_marker
>  - Fix packing/unpacking adapters, fix some miscelaneous issues, address comment
>  - Support NULLABLE_NON_ATOMIC in the JITs

Thanks a lot for your reviews!

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PR Comment: https://git.openjdk.org/valhalla/pull/1970#issuecomment-3835869422