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

[Vladimir Kozlov]

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

GHA `linux-x64-hs-minimal` failure is not related to changes:

2024-04-04T00:07:46.9654262Z ##[warning]Failed to download action 'https://api.github.com/repos/actions/github-script/tarball/60a0d83039c74a4aee543508d2ffcb1c3799cdea'. Error: The request was canceled due to the configured HttpClient.Timeout of 100 seconds elapsing.
2024-04-04T00:07:46.9656929Z ##[warning]Back off 22.252 seconds before retry.
2024-04-04T00:08:52.1252710Z ##[error]The SSL connection could not be established, see inner exception.

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PR Comment: https://git.openjdk.org/jdk/pull/18554#issuecomment-2035859221