RFR: 8368465: [leyden] Improve precompiler method selection code [v3]

[Aleksey Shipilev]

On Fri, 17 Oct 2025 07:04:26 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Forked from [JDK-8366681](https://bugs.openjdk.org/browse/JDK-8366681): there are still some cleanups/performance improvements possible. Current selection code is a bit hairy, and turns out the changes I made for previous patch improve performance.
>> 
>> Notable improvements:
>>  1. Push the compilation level filters downwards. This allows compiling A2 from T2/T3 code more easily, and allows to implement policies for compiling on any A* level based on observing top-compiled T* levels.
>>  2. Sort methods by hotness and code size. This looks to have a positive effect on shorter workloads, I suspect because we are avoiding a lot of C1 compilations by preloading hottest code first.
>> 
>> Additional testing:
>>  - [x] Performance tests (see comments)
>>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>
> Aleksey Shipilev 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:
> 
>  - Merge branch 'premain' into JDK-8368465-precompiler-method-select
>  - Merge branch 'premain' into JDK-8368465-precompiler-method-select
>  - Touchup
>  - Touchups
>  - Fix

Ready for review, folks. There are performance benefits of doing this, very apparently.

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PR Comment: https://git.openjdk.org/leyden/pull/99#issuecomment-3414157076