RFR: 8329332: Remove CompiledMethod and CodeBlobLayout classes

[Amit Kumar]

On Fri, 29 Mar 2024 19:35:45 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.

I performed the build + testing `{fastdebug, release, slowdebug} X {tier1}`  on `s390x` and result looks fine.

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PR Comment: https://git.openjdk.org/jdk/pull/18554#issuecomment-2029655163