RFR: 8329332: Remove CompiledMethod and CodeBlobLayout classes [v3]

[Axel Boldt-Christmas]

On Thu, 4 Apr 2024 00:05:20 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Revert [JDK-8152664](https://bugs.openjdk.org/browse/JDK-8152664) RFE [changes](https://github.com/openjdk/jdk/commit/b853eb7f5ca24eeeda18acbb14287f706499c365) which was used for AOT [JEP 295](https://openjdk.org/jeps/295) implementation in JDK 9. The code was left in HotSpot assuming it will help in a future. But during work on Leyden we decided to not use it. In Leyden cached compiled code will be restored in CodeCache as normal nmethods: no need to change VM's runtime and GC code to process them.
>> 
>> I may work on optimizing `CodeBlob` and `nmethod` fields layout to reduce header size in separate changes. In these changes I did simple fields reordering to keep small (1 byte) fields together.
>> 
>> I do not see (and not expected) performance difference with these changes.
>> 
>> Tested tier1-5, xcomp, stress. Running performance testing.
>> 
>> I need help with testing on platforms which Oracle does not support.
>
> Vladimir Kozlov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Address comments
>  - Merge branch 'master' into 8329332
>  - Removed not_used state of nmethod
>  - remove trailing whitespace
>  - 8329332: Remove CompiledMethod and CodeBlobLayout classes

There is a stale comment in `test/jdk/com/sun/jdi/EATests.java:1288`


-// (See CompiledMethod::is_at_poll_return())
+// (See nmethod::is_at_poll_return())

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PR Review: https://git.openjdk.org/jdk/pull/18554#pullrequestreview-1978884423