In legacy CDS, Java objects used by certain classes are computed ahead of time using "object subgraphs"
https://github.com/openjdk/jdk/blob/1bbbce75c5e68429c2a32519eb3c36d964dcdf57/src/hotspot/share/cds/heapShared.cpp#L168-L171 Examples of subgraphs: - `java.lang.Integer$IntegerCache::cache` - `jdk.internal.module.ArchivedBootLayer::bootLayer` The implementation requires special code (in both Java and C++) to be executed when a CDS archive is created or loaded. As a result, we have an execution model that's difficult to implement/extend and the behavior is hard to understand. To move towards the AOT Cache Snapshot Model ([JDK-8365645](https://bugs.openjdk.org/browse/JDK-8365645)) we should replace the subgraphs with the use of `@AOTSafeClassInitializer`, and if necessary, `@AOTRuntimeSetup`. This will simplify the current implementation, and make it possible to extend AOT-initializations to more core classes. Note, the use of `@AOTSafeClassInitializer` requires `-XX:+AOTClassLinking`. For the time being, we retain the old CDS object subgraph code to cover the `-XX:-AOTClassLinking` cases. Such code will be marked with comments like `/* Legacy CDS archive support (to be deprecated) */`. All future AOT creation of Java objects will be done with `@AOTSafeClassInitializer`. ------------- Commit messages: - 8373392: Replace CDS object subgraphs with @AOTSafeClassInitializer Changes: https://git.openjdk.org/jdk/pull/28736/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28736&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8373392 Stats: 602 lines in 29 files changed: 368 ins; 186 del; 48 mod Patch: https://git.openjdk.org/jdk/pull/28736.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28736/head:pull/28736 PR: https://git.openjdk.org/jdk/pull/28736
