[lworld] Integrated: 8374800: [lworld] Add a NULLABLE_NON_ATOMIC_FLAT layout

[Frederic Parain]

On Mon, 24 Mar 2025 20:49:25 GMT, Frederic Parain <fparain at openjdk.org> wrote:

> Strict final instance fields are not subject to concurrent writes during a read access, so they can be flattened even if they are nullable and bigger than 64 bits. The NULLABLE_NON_ATOMIC_FLAT layout is added for this particular case.
> This new layout can also be used in the special case of nullable empty value classes, because their payload contains a single entry, the null-marker, which is naturally atomic.

This pull request has now been integrated.

Changeset: 0c01b973
Author:    Frederic Parain <fparain at openjdk.org>
URL:       https://git.openjdk.org/valhalla/commit/0c01b9734abc1ff8af4c0f79c85746fcb8debf43
Stats:     760 lines in 22 files changed: 589 ins; 10 del; 161 mod

8374800: [lworld] Add a NULLABLE_NON_ATOMIC_FLAT layout

Reviewed-by: coleenp

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PR: https://git.openjdk.org/valhalla/pull/1407