RFR: 8339939: [JVMCI] Don't compress abstract and interface Klasses

[Thomas Stuefe]

On Wed, 11 Sep 2024 13:57:31 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> https://github.com/openjdk/jdk/pull/19157 disallows storing abstract and interface Klasses in class metaspace. JVMCI has to respect this and avoids compressing abstract and interface Klasses
>
> src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotConstant.java line 29:
> 
>> 27: /**
>> 28:  * Marker interface for hotspot specific constants.
>> 29:  */
> 
> Let's take this opportunity to improve this javadoc:
> 
> /**
>  * A value in a space managed by Hotspot (e.g. heap or metaspace).
>  * Some of these values can be referenced with a compressed pointer (32 bits)
>  * instead of a full word-sized pointer.
>  */

drive-by comment, 32-bit is an implementation detail. The width of a narrowKlass will be adjustable with the upcoming JEP450. Referring to 32 bit may be obsolete soon.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20949#discussion_r1763011967