[lworld] RFR: 8376221: [lworld] Do not store array of InlineLayoutInfo for all InstanceKlasses [v6]

[duke]

On Mon, 2 Feb 2026 09:53:04 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

>> Hello,
>> 
>> Please refer to the JBS issue for a more detailed description of the background of this change. In summary, I suggest we only keep the array of InlineLayoutInfo for InstanceKlasses which need it, which are Klasses that have fields that have been inlined.
>> 
>> To make the transition to this easier, I suggest we change the following properties in FieldLayoutBuilder: 
>> 
>> _has_inline_type_fields
>> _has_flattening_information
>> 
>> to
>> 
>> _has_inlineable_fields
>> _has_inlined_fields
>> 
>> The `_has_inlineable_fields` property is only used for printing and `_has_inlined_fields` is the property we expose out to the ClassFileParser, telling us that this class has inlined fields, so the array of InlineLayoutInfo must be "preserved" and is possible to read from. Hence, the array is now only safe to access if `InstanceKlass::has_inlined_fields` is true, or simply if the actual field being accessed is flat (`fieldDescriptor::is_flat`).
>> 
>> I only found one place (in ciReplay.cpp) where we access the array of InlineLayoutInfo even though we might not have any inlined fields and only fields that are inlineable. I've changed this to use the normal "reference" path for fields that aren't flat.
>> 
>> Testing:
>> * Oracle's tier1-5, hotspot_valhalla and jdk_valhalla
>
> Joel Sikström has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Move InlineKlass::cast() to callers
>  - Add abstract check to field_is_inlineable

@jsikstro 
Your change (at version cb80bac989c98ff2423b88c88a4f08d3bccfcb68) is now ready to be sponsored by a Committer.

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

PR Comment: https://git.openjdk.org/valhalla/pull/1966#issuecomment-3840823160