[lworld] RFR: 8361352: [lworld] Weird interaction between OSR and value class instances [v2]

[Marc Chevalier]

On Mon, 25 Aug 2025 07:17:16 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

>> Marc Chevalier has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Rephrase summary
>>  - +copyright
>
> src/hotspot/share/ci/ciType.cpp line 151:
> 
>> 149:   assert(type->is_inlinetype()
>> 150:              // An abstract value type is an instance_klass
>> 151:              || (type->is_instance_klass() && type->as_instance_klass()->flags().is_abstract() && !type->as_instance_klass()->flags().is_identity())
> 
> Just wondering, is the `type->as_instance_klass()->flags().is_abstract()` condition even needed? Same in `ciTypeFlow::get_start_state()`.

Probably not. An instance class without identity must be an abstract value class. At least, I don't see another way... But just to be sure, I'm running some tests.

> test/hotspot/jtreg/compiler/valhalla/inlinetypes/LarvalDetectionAboveOSR.java line 29:
> 
>> 27:  * @summary In OSR compilation, value objects coming from above the OSR start
>> 28:  * must be correctly found to be early larval so we know they are
>> 29:  * immutable, and they can be scalarized.
> 
> I suggest to rephrase this: "to be early larval so we know they are immutable" is confusing because early larvals are **mutable**.

Wow, yeah, I see what I wanted to say, but it's terrible! I've tried something else, hopefully better.

-------------

PR Review Comment: https://git.openjdk.org/valhalla/pull/1531#discussion_r2297532414
PR Review Comment: https://git.openjdk.org/valhalla/pull/1531#discussion_r2297539481