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

[Joel Sikström]

On Mon, 16 Feb 2026 14:51:52 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

> Hello,
> 
> We should consider moving the enum ArrayProperties from ArrayKlass to its own class, ArrayProperties. In addition to making the code easier to read and understand, this allows us to have explicit setters/getters, replacing the bit-fiddling expressions that are used in many places. The ArrayProperties-specific methods in ArrayKlass have been moved to be methods in the new ArrayProperties class instead.
> 
> Perhaps the most controversial change in this PR is the removal of `ArrayKlass::ArrayProperties::DEFAULT` in favor of using a default constructor for ArrayProperties. The semantics are still the same, i.e., asking `.is_null_restricted()` or `.is_non_atomic()` will be false for the default constructed property. With this I've also removed the unused fields from ArrayProperties (DUMMY and comments).
> 
> I did consider using define macros to generate enum+getters+setters, but I opted for the stamped-out version instead.
> 
> Testing:
> * Running through tier1-2

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!

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PR Review Comment: https://git.openjdk.org/valhalla/pull/2114#discussion_r2812812833