[lworld] RFR: 8376221: [lworld] Do not store array of InlineLayoutInfo for all InstanceKlasses [v5]

[Frederic Parain]

On Mon, 26 Jan 2026 10:20:53 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> Joel Sikström has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 11 additional commits since the last revision:
>> 
>>  - Merge branch 'lworld' into JDK-8376221_inlinelayoutinfo_array_optimization
>>  - LayoutKind assertion for flat fields
>>  - Remove mention of 'warning' in comment
>>  - Exception check should really be an assert
>>  - Move inlineable check to static helper
>>  - Comment for second CLEAR_PENDING_EXCEPTION
>>  - Clear exception before setting inline klass
>>  - Split assert in field sorting methods
>>  - IOOB assert message
>>  - InstanceKlass instead of Klass for set_inline_layout_info_klass
>>  - ... and 1 more: https://git.openjdk.org/valhalla/compare/7c7ac5ac...b934da63
>
> src/hotspot/share/classfile/classFileParser.cpp line 6341:
> 
>> 6339:       _must_be_atomic, _layout_info, _inline_layout_info_array);
>> 6340:   lb.build_layout();
>> 6341:   _has_inlined_fields = _layout_info->_has_inlined_fields;
> 
> More of a questions to the long-time Valhalla devs: I'm a little curious why the parser has booth of these fields containing the same value?

Historical reasons. The _layout_info structure was added late, and the previous ways to handle inline fields information was not properly refactored.
The ClassFilerParser gets the _layout_info instance before creating the InstanceKlass instance and keeps it until the InstanceKlass instance has been fully initialized, so it is safe to refactor the code to remove ClassFileParser::_has_inline_fields and refactor ClassFilerParser::has_inline_fields() to return _layout_info->_has_inlined_fields.
Note: currently, the only client of ClassFilerParser::has_inline_fields() is the InstanceKlass constructor.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1966#discussion_r2743487176