RFR: 8298099: [JVMCI] decouple libgraal from JVMCI module at runtime [v6]

[Alan Bateman]

On Tue, 6 Dec 2022 16:06:34 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> Libgraal is compiled ahead of time and should not need any JVMCI Java code to be dynamically loaded at runtime. Prior to this PR, this is not the case due to:
>> 
>> * Code to copy system properties from the HotSpot heap into the libgraal heap. This is in `jdk.vm.ci.services.Services.initializeSavedProperties(byte[])` and `jdk.vm.ci.services.Services.serializeSavedProperties()`. This code should be moved to `java.base/jdk.internal.vm.VMSupport`.
>> * Code to translate exceptions from the HotSpot heap into the libgraal heap and vice versa. This code should be moved from `jdk.internal.vm.ci//jdk.vm.ci.hotspot.TranslatedException` to `java.base/jdk.internal.vm.VMSupport`.
>> 
>> This PR makes the above changes. As a result, it's possible to build a JDK image that includes (and uses) libgraal but does not include `jdk.internal.vm.ci` or `jdk.internal.vm.compiler`. This both reduces footprint and better isolates the JAVMCI and the Graal compiler as accessing these components from Java code is now impossible.
>
> Doug Simon has updated the pull request incrementally with four additional commits since the last revision:
> 
>  - formatting to avoid very long lines [skip ci]
>  - removed debug code [skip ci]
>  - clarify Properties filtering [skip ci]
>  - remove debug code [skip ci]

src/java.base/share/classes/jdk/internal/vm/TranslatedException.java line 128:

> 126:         // Try create with reflection first.
> 127:         try {
> 128:             Class<?> cls = Class.forName(className);

A question about the Class.forName usage here. Class.forName uses the defining class loader of the current class so I'm wondering if the exceptions to be decoded are always of a type defined to the boot loader? jdk.internal.vm.ci is defined to the boot loader so this code hasn't really changed, it's just "new" to java.base in this PR.

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PR: https://git.openjdk.org/jdk/pull/11513