[lworld] Integrated: 8373864: [lworld] Hide and rename InstanceKlassFixedBlock

[Stefan Karlsson]

On Wed, 17 Dec 2025 10:21:24 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> Sub-classes of `InstanceKlass` can't have C++ fields because they would end up overlayed on top of the vtable and other dynamically sized sections of the `InstanceKlass` object.
> 
> To handle that the `InlineKlass` has a companion class named `InlineKlassFixedBlock`, which lists all the member fields that belongs to the InlineKlass, and an instance of that gets stamped into the `InlineKlass` object after the parts that are provided by the `InstanceKlass`.
> 
> I propose a few changes:
> 
> 1) Move `InlineKlassFixedBlock` away from instanceKlass.hpp and place it inside inlineKlass.hpp instead.
> 
> 2) Nest `InlineKlassFixedBlock` it inside `InlineKlass`. It's only `InlineKlass `(and the compilers) that touch these fields, so it doesn't have to be a public, top-level class.
> 
> 3) Rename it from `InlineKlassFixedBlock` to `InlineKlass::Members`. I think that "fixed block" term is unclear and doesn't help the reader understand its role in the `InlineKlass`. Hopefully, the name `Members` is a clearer.
> 
> WDYT?

This pull request has now been integrated.

Changeset: d586e57d
Author:    Stefan Karlsson <stefank at openjdk.org>
Committer: Frederic Parain <fparain at openjdk.org>
URL:       https://git.openjdk.org/valhalla/commit/d586e57d7488461e808e7cb566586d7112b72dc6
Stats:     222 lines in 15 files changed: 98 ins; 53 del; 71 mod

8373864: [lworld] Hide and rename InstanceKlassFixedBlock

Reviewed-by: phubner, fparain

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PR: https://git.openjdk.org/valhalla/pull/1812