RFR: 8259368: Zero: UseCompressedClassPointers does not depend on UseCompressedOops

[Andrew Haley]

On Thu, 7 Jan 2021 13:39:37 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> JDK-8241825 decoupled `UseCompressedClassPointers` and `UseCompressedOops`, and introduced `COMPRESSED_CLASS_POINTERS_DEPENDS_ON_COMPRESSED_OOPS` that platforms can set to say if their generated code is ready for this decoupling.
> 
> Zero defaults to `true` for that flag, meaning the flags are still coupled. But there is not actual coupling: Zero delegates all this work to VM code, which handles everything correctly. This makes at least one test fail with Zero:
> 
> $ CONF=linux-x86_64-zero-fastdebug make exploded-test TEST=runtime/CompressedOops/CompressedClassPointers.java
> java.lang.RuntimeException: 'Narrow klass base: 0x0000000000000000' missing from stdout/stderr
> ...
> 
> Additional testing:
>  - [x] Linux x86_64 Zero `runtime/CompressedOops/` tests

Marked as reviewed by aph (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/1973