RFR: 8360163: Create annotations to mark dumping method handles and runtime setup required classes [v8]

[Ioi Lam]

On Wed, 2 Jul 2025 18:47:58 GMT, Chen Liang <liach at openjdk.org> wrote:

>> I have updated this patch to avoid a redundant `runtimeSetup` annotation - we have agreed that the requirement for setup is a side effect of initialization, and such methods in AOTCI classes must be automatically recognized. This latest revision implements that model.
>> 
>> I intentionally avoided handling Class and ClassLoader `resetArchivedStates` and `MethodType::assemblySetup` - we talked about a generic `assemblyCleanup` method, but I did not find out where is the best place to call such a method in the assembly phase. We cna handle this in a subsequent patch.
>> 
>> In particular, please review the new AOT.md design document - I split it from the AOTCI annotation to prevent jamming; we can put general AOT information there when we have more AOT-specific annotations.
>> 
>> ---
>> 
>> Old description:
>> Currently, the list of classes that have <clinit> interdependencies and those that need runtimeSetup are maintained in a hardcoded list in CDS. This makes it risky for core library developers as they might introduce new interdependencies and observe CDS to fail. By moving the mechanism of these lists to core library annotations as a first step, we can gradually expose the AOT contracts as program semantics described by internal annotations, and also helps us to explore how we can expose these functionalities to the public later.
>
> Chen Liang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Documentation

Changes requested by iklam (Reviewer).

src/hotspot/share/cds/aotClassInitializer.cpp line 219:

> 217:     // MethodHandleStatics is an example of a class that must NOT get the aot-init treatment,
> 218:     // because of its strong reliance on (a) final fields which are (b) environmentally determined.
> 219:     if (ik->has_aot_safe_initializer()) {

I think the above 4 lines of comments can be deleted, as this topic is already covered in AOTSafeClassInitializer.java.

src/hotspot/share/classfile/classFileParser.cpp line 5171:

> 5169:       InstanceKlass* intf = _transitive_interfaces->at(i);
> 5170:       if (intf->class_initializer() != nullptr) {
> 5171:         if (!intf->has_aot_safe_initializer()) {

I think this is better, so you don't need to annotate a supertypes that have no `<clinit>`


if (intf->class_initializer() != nullptr && !intf->has_aot_safe_initializer()) {

src/hotspot/share/oops/instanceKlassFlags.hpp line 58:

> 56:     flag(has_final_method                   , 1 << 13) /* True if klass has final method */ \
> 57:     flag(has_aot_safe_initializer           , 1 << 14) /* has @AOTSafeClassInitializer annotation */ \
> 58:     flag(is_runtime_setup_required          , 1 << 15) /* has a runtimeSetup method to be called */ \

This information is useful only during CDS dumping. Since `_flags` has limited width (only 16 bits) we should avoid using these bits but rather put the information inside `DumpTimeClassInfo`. However, there's a complication here, as `DumpTimeClassInfo` is not yet created when you call `set_has_aot_safe_initializer()`.

I think you can go ahead with the current design. I will make a follow-up PR to move the creation of `DumpTimeClassInfo` to an earlier time. Then I'll move these two bits into `DumpTimeClassInfo`. That way we can accommodate more annotations in the future.

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PR Review: https://git.openjdk.org/jdk/pull/25922#pullrequestreview-2980604461
PR Review Comment: https://git.openjdk.org/jdk/pull/25922#discussion_r2180955211
PR Review Comment: https://git.openjdk.org/jdk/pull/25922#discussion_r2180988960
PR Review Comment: https://git.openjdk.org/jdk/pull/25922#discussion_r2180982768