[lworld] RFR: 8378000: [lworld] Move ArrayProperties to its own class [v4]

[Frederic Parain]

On Mon, 16 Feb 2026 14:53:31 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

>> Joel Sikström has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:
>> 
>>  - Cleanups of earlier commits
>>  - Merge branch 'lworld' into JDK-8378000_array_properties
>>  - Semi-builder pattern for ArrayProperties
>>  - Add assert to check for invalid flags/bits
>>  - Change type to be consistent with compiler type
>>  - Braces around if-statement
>>  - 8378000: [lworld] Move ArrayProperties to its own class
>
> src/hotspot/share/oops/objArrayKlass.cpp line 425:
> 
>> 423:     if (next_refined_array_klass() == nullptr) {
>> 424:       ObjArrayKlass* first = this;
>> 425:       if (!is_refArray_klass() && !is_flatArray_klass() && (props.is_null_restricted() || props.is_non_atomic())) {
> 
> The check for this was `props != ArrayKlass::ArrayProperties::DEFAULT` before this, which included the INVALID state. I ran this through tier1-2 with the assert `assert(!props.is_invalid(), "surely");`, which did not hit.
> 
> I'd appreciate feedback on if we still want to check for the invalid property here!

This method should never be called with an INVALID property set.
Only the `ObjArrayklass` instance representing the Java type is allowed to have an INVALID property set (in fact it must because it is an unrefined array type).
The method `ObjArrayKlass::klass_from_description()` is used to find or create a refined array type, and refined array types must have a valid array property set.
I'd suggest to add the assert you mentioned to ensure no INVALID props argument is passed.
I'd also suggest to keep the test like this:
` if (!is_refArray_klass() && !is_flatArray_klass() && (props != ArrayProperties::Default())) {`
because it would still be correct after the introduction of new properties for final arrays and volatile arrays.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/2114#discussion_r2853986690