[lworld] RFR: 8353432: [lworld] Deoptimization needs to handle nullable, flat fields in non-value class holders

[Quan Anh Mai]

On Sun, 1 Jun 2025 00:59:53 GMT, f <duke at openjdk.org> wrote:

>> Hi,
>> 
>> This patch adds handling of nullable flat fields in non-value class holder. Currently, we add all the fields to the safepoint, then add all the null markers. I decide to change this to adding the null marker of a flat field right after all the subfields of it. It makes the shape similar to how we pass nullable flat fields in the ABI, as well as simplifies the implementation since we do not have to keep track of all null markers when traversing the object payload.
>> 
>> Please take a look and leave your reviews, thanks a lot.
>
> @merykitty Hi, valhalla is almost ready for experimental use now, right?

@SidneyLann Valhalla is ready for experimental use, you can either build the project from source (build instructions can be found [here](https://openjdk.org/groups/build/doc/building.html)) or you can grab a prebuilt package [here](https://builds.shipilev.net/). Please give it a try and report to us any issue you find, it would be a great help in the stabilization of Valhalla.

If you want to know whether Valhalla can be released to mainline soon then the answer is we don't know and we are trying our best. I believe an act of trying, reporting issues, and even contributing will help Valhalla to land sooner.

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PR Comment: https://git.openjdk.org/valhalla/pull/1478#issuecomment-2926632410