RFR: 8367719: Refactor JNI code that uses class_to_verify_considering_redefinition()

[Coleen Phillimore]

On Tue, 16 Sep 2025 02:44:26 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Simplify the boilerplate code in jvm.cpp that calls `JvmtiThreadState::class_to_verify_considering_redefinition()`, and reduce the number of `InstanceKlass::cast()` calls.
> 
> I also changed a few fields/arguments from `Klass*` to `InstanceKlass*` as these are used exclusively with `InstanceKlass*`.

This looks good pending David's and my suggested changes (hope it works).
I sort of think there's no need for the Klass* version of get_class_considering_redefinition since its callers seem to really want an InstanceKlass. Since it's jvm.cpp, you can probably verify that it's never Klass in these callers.

src/hotspot/share/prims/jvm.cpp line 2265:

> 2263: inline Klass* get_klass_considering_redefinition(jclass cls, JavaThread *thread) {
> 2264:   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(cls));
> 2265:   k = JvmtiThreadState::class_to_verify_considering_redefinition(k, thread);

Suggestion:

 return JvmtiThreadState::class_to_verify_considering_redefinition(k, thread);

src/hotspot/share/prims/jvm.cpp line 2266:

> 2264:   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(cls));
> 2265:   k = JvmtiThreadState::class_to_verify_considering_redefinition(k, thread);
> 2266:   return k;

Suggestion:

src/hotspot/share/prims/jvm.cpp line 2271:

> 2269: inline InstanceKlass* get_instance_klass_considering_redefinition(jclass cls, JavaThread *thread) {
> 2270:   InstanceKlass* ik = java_lang_Class::as_InstanceKlass(JNIHandles::resolve_non_null(cls));
> 2271:   ik = JvmtiThreadState::class_to_verify_considering_redefinition(ik, thread);

Suggestion:

  return JvmtiThreadState::class_to_verify_considering_redefinition(ik, thread);

src/hotspot/share/prims/jvm.cpp line 2272:

> 2270:   InstanceKlass* ik = java_lang_Class::as_InstanceKlass(JNIHandles::resolve_non_null(cls));
> 2271:   ik = JvmtiThreadState::class_to_verify_considering_redefinition(ik, thread);
> 2272:   return ik;

Suggestion:

src/hotspot/share/prims/jvm.cpp line 2291:

> 2289: 
> 2290: JVM_ENTRY(const char*, JVM_GetClassNameUTF(JNIEnv *env, jclass cls))
> 2291:   Klass* k = get_klass_considering_redefinition(cls, thread);

Even if it's a redefined class, it'll have the same name so this isn't necessary.

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PR Review: https://git.openjdk.org/jdk/pull/27303#pullrequestreview-3230659598
PR Review Comment: https://git.openjdk.org/jdk/pull/27303#discussion_r2352957988
PR Review Comment: https://git.openjdk.org/jdk/pull/27303#discussion_r2352958544
PR Review Comment: https://git.openjdk.org/jdk/pull/27303#discussion_r2352959692
PR Review Comment: https://git.openjdk.org/jdk/pull/27303#discussion_r2352960240
PR Review Comment: https://git.openjdk.org/jdk/pull/27303#discussion_r2352970204