RFR: 8352003: Support --add-opens with -XX:+AOTClassLinking [v3]

[Ioi Lam]

On Mon, 21 Apr 2025 06:20:46 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

>> This RFE allows --add-opens to be specified for AOT cache creation. AOT cache can be used during production run with --add-opens option as long as the same set of options is used during assembly phase.
>> 
>> Passed tiers 1 - 4 testing.
>
> Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   @iklam comment

src/java.base/share/classes/jdk/internal/module/ModuleBootstrap.java line 165:

> 163:             BootLoader.getUnnamedModule(); // trigger <clinit> of BootLoader.
> 164:             CDS.defineArchivedModules(ClassLoaders.platformClassLoader(), ClassLoaders.appClassLoader());
> 165:             boolean extraExportsOrOpens = addExtraExportsAndOpens(bootLayer);

(1) The returned value of `addExtraExportsAndOpens()` is not used. So I think this function can be changed to `void`, and all occurrences of the local variable `extraExportsOrOpens` can be removed.

(2) I traced the code paths that depend on the effects of `--add-opens` and `--add-exports`. It Looks like some of the effects are recorded in the `java.lang.Module$ReflectionData::export` table:

https://github.com/openjdk/jdk/blob/684d3b336e9cb31707d35e75f9b785e04e1fdbee/src/java.base/share/classes/java/lang/Module.java#L398C2-L412


        /**
         * A module (1st key) exports or opens a package to another module
         * (2nd key). The map value is a map of package name to a boolean
         * that indicates if the package is opened.
         */
        static final WeakPairMap<Module, Module, Map<String, Boolean>> exports =
            new WeakPairMap<>();


This table is *not* stored as part of the `ArchivedBootLayer`, so we must re-initialize this table in the production run. @AlanBateman could you confirm that this is correct.

Eventually, we should enhance the `ArchivedBootLayer` to also include the tables in `Module$ReflectionData`. That will obviate the call to `addExtraExportsAndOpens()` and save a few bytecodes during start-up (but the overall impact would be small, so it's not critical in the current PR). Because these tables use WeakReference, we need to wait for [JDK-8354897](https://bugs.openjdk.org/browse/JDK-8354897).

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PR Review Comment: https://git.openjdk.org/jdk/pull/24695#discussion_r2052840896