RFR: 8317269: Store old classes in linked state in AOT cache [v5]

[Coleen Phillimore]

On Mon, 1 Sep 2025 00:57:33 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> src/hotspot/share/classfile/systemDictionaryShared.cpp line 542:
>> 
>>> 540: }
>>> 541: 
>>> 542: Klass* SystemDictionaryShared::find_verification_dependency_bottom_class(InstanceKlass* k, Symbol* dependency_class_name) {
>> 
>> Why don't you have this return InstanceKlasss so that the callers don't have to check the same thing. What you want is the bottom InstanceKlass so for [Lfoo; - you want foo.  Since class foo is the thing you care about.  Maybe the comment about why you return nullptr from check_verification_dependency_exclusion() could be here instead.
>> 
>> These names are a bit repetative, can you just call this find_bottom_instance_klass() and maybe it could be used for other things too.
>
> The problem is if `k` is the ObjArrayKlass of `[[I`, then `k->bottom_klass()` is `[I`, which is not an InstanceKlass. If we change the return type to `InstanceKlass*`, then we would have to return `nullptr`. However, that would make it more difficult to explain the following case (I've updated the comments):
> 
> 
> bool SystemDictionaryShared::check_verification_dependency_exclusion(InstanceKlass* k, Symbol* dependency_class_name) {
>   Klass* dependency_bottom_class = find_verification_dependency_bottom_class(k, dependency_class_name);
>   if (dependency_bottom_class == nullptr) {
>     // Dependency_class_name has not yet been loaded. This happens when the new verifier was checking
>     // if dependency_class_name is assignable to an interface, and found the answer without resolving
>     // dependency_class_name.
>     //
>     // Since this class is not even loaded, it surely cannot be excluded.
>     return false;
>   }

This doesn't seem bad.  You could say "Not loaded or bottom class is not an instanceKlass."  Do you need to say what the verifier was doing here?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26754#discussion_r2323224309