RFR: 8348570: CTW: Expose the code hidden by uncommon traps [v4]

[Aleksey Shipilev]

On Wed, 5 Feb 2025 15:23:07 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> We have been looking at some related compiler behaviors, and realized that in the absence of profiling data, C2 routinely uncommon-traps a lot of code that is presumed to be never executed. This apparently is a norm in CTW tests: CTW runners never execute code, and so only the most basic java.base classes are having any profile. This seems to limit the scope of CTW testing.
>> 
>> I think we need to run CTW in the mode that exposes more code to the compiler optimizations.
>> 
>> Case in point: [JDK-8348572](https://bugs.openjdk.org/browse/JDK-8348572), which reliably fails with more aggressive compilation mode. 
>> 
>> Additional testing:
>>  - [x] Linux x86-64 server fastdebug, `applications/ctw/modules`
>>  - [x] Linux AArch64 server fastdebug, `applications/ctw/modules`
>
> 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 four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8348570-ctw-uncommon-traps
>  - Merge branch 'master' into JDK-8348570-ctw-uncommon-traps
>  - Also do markMethodProfiled for extra scope
>  - Fix

`applications/ctw/modules` passes for me on bigger machines as well, so I think we are ready to go.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/23296#issuecomment-2637306557