RFR: 8350488: [leyden] Experimental AOT-only mode

[Vladimir Kozlov]

On Fri, 21 Feb 2025 10:36:19 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> There are interesting use cases where we want the AOT-only mode. We can emulate this in current Leyden prototype by relying on preload code, and stopping any profiling, which would naturally lead to no JIT compilations. This would also make interpreter code a bit faster in case we need to fall back there. This mode looks also helpful for studying the compiler dynamics.
> 
> Additional testing:
>  - [x] Eyeballing compilation logs with `-XX:+PreloadOnly`
>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>  - [x] Linux x86_64 server fastdebug, `runtime/cds` with `-XX:+PreloadOnly`

Looks good. Next step could be to cache only preload code during training to reduce size of cached data and time to load it. You don't need to save profiling data too.

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Marked as reviewed by kvn (Committer).

PR Review: https://git.openjdk.org/leyden/pull/44#pullrequestreview-2633955110