[lworld] RFR: 8311219: [lworld] VM option "InlineFieldMaxFlatSize" cannot work well [v4]

[Xiaohong Gong]

On Thu, 7 Sep 2023 06:37:25 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
>> 
>>  - Merge 'valhalla:lworld' into JDK-8311219
>>  - Fix "assert(field->type()->as_inline_klass()->is_initialized()) failed: Must be"
>>  - Not flatten L-descriptor value object field even it is final
>>  - 8311219: [lworld] VM option "InlineFieldMaxFlatSize" cannot work well
>
> src/hotspot/share/classfile/fieldLayoutBuilder.cpp line 761:
> 
>> 759:             // volatile fields are currently never flatten, this could change in the future
>> 760:           }
>> 761:           if (!(too_big_to_flatten | too_atomic_to_flatten | too_volatile_to_flatten)) {
> 
> Please also add an IR framework test to check primitive class final/non-final field flattening, given that InlineTypeNode are removed during Optimization hence such a check has to be done on post Parse IR.

The main problem for me is how to check the flatten status for an `InlineTypeNode`. Maybe we can check the decode operation generated by the field accessing (or loading) to an primitive class field. Any better idea for this?

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PR Review Comment: https://git.openjdk.org/valhalla/pull/888#discussion_r1318229377