RFR: 8345826: Do not automatically resolve jdk.internal.vm.ci when libgraal is used [v2]

[Ioi Lam]

On Fri, 16 May 2025 13:16:30 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> The `EnableJVMCI` flag currently serves 2 purposes:
>> * Guards VM code ([example](https://github.com/openjdk/jdk/blob/b1e778d9d2ad13ee5f1ed629a8805008580f86c0/src/hotspot/share/runtime/sharedRuntime.cpp#L652)).
>> * [Adds](https://github.com/openjdk/jdk/blob/b1e778d9d2ad13ee5f1ed629a8805008580f86c0/src/hotspot/share/runtime/arguments.cpp#L1804) `jdk.internal.vm.ci` to the root module set.
>> 
>> This PR changes nothing about the first point.
>> 
>> On the second point, to use the `jdk.internal.vm.ci` module when libgraal is enabled, `--add-modules=jdk.internal.vm.ci` must be specified.
>> If libgraal is not enabled, +EnableJVMCI will continue to add `jdk.internal.vm.ci` to the root module set.
>> 
>> The primary motivation is to make use of libgraal compatible with `-XX:+AOTClassLinking`. This flag relies on the root module set archive created in a training run. If the root module set is different in the production run, the AOTClassLinking [optimizations](https://bugs.openjdk.org/browse/JDK-8342279) are disabled. As `jdk.internal.vm.ci` is not resolved in the training run, it must not be resolved in production run. As such, `-XX:+EnableJVMCI` must not cause resolution of `jdk.internal.vm.ci`, otherwise libgraal will not have the startup advantages of AOTClassLinking.
>
> Doug Simon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   resolve jdk.internal.vm.ci if +EnableJVMCI and -UseJVMCINativeLibrary

src/hotspot/share/runtime/arguments.cpp line 1814:

> 1812:     }
> 1813:     PropertyList_unique_add(&_system_properties, "jdk.internal.vm.ci.enabled", "true",
> 1814:         AddProperty, UnwriteableProperty, InternalProperty);

What's the purpose of the `jdk.internal.vm.ci.enabled` property? Should it be enabled only if the `jdk.internal.vm.ci` module is added?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25240#discussion_r2093091052