Integrated: 8350550: Preload classes from AOT cache during VM bootstrap

[Ioi Lam]

On Thu, 17 Jul 2025 22:38:48 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> This PR loads the classes for the boot/platform/app loaders with `AOTLinkedClassBulkLoader::preload_classes()`. This happens at the very beginning of `vmClasses::resolve_all()`, before any Java code is executed. 
> 
> - We essentially iterate over all the classes inside the `AOTLinkedClassTable` and adds them into the system dictionary using the new method `SystemDictionary::preload_class()`.
> - `SystemDictionary::preload_class(..., k)` is lightweight because it's called in a single thread after all super types of `k` have been loaded. So most of the complicated work (such as place holders, circularity detection, etc) in `SystemDictionary::resolve_or_null(..., k)` can be skipped. We also don't need to call into `ClassLoader::load_class()` as the boot/platform/app loaders are well-behaved.
> - In the assembly phase, we record the mirror, package, protection domain, code source, etc, of these classes. So there's no need to programmatically create them in the production run. See `HeapShared::copy_java_mirror()` and also changes in ClassLoader.java and SecureClassLoader.java.

This pull request has now been integrated.

Changeset: fd30ae98
Author:    Ioi Lam <iklam at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fd30ae988bc512b5d2a5a3fd1bc1ed351af974c7
Stats:     941 lines in 43 files changed: 534 ins; 236 del; 171 mod

8350550: Preload classes from AOT cache during VM bootstrap

Reviewed-by: kvn, heidinga, asmehra

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PR: https://git.openjdk.org/jdk/pull/26375