RFR: 8348570: CTW: Expose the code hidden by uncommon traps [v2]

[Vladimir Kozlov]

On Fri, 24 Jan 2025 17:09:53 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. We cannot integrate this PR until that bug is fixed. But we can discuss if this makes sense, and/or we want some other options included to expand CTW testing.
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Also do markMethodProfiled for extra scope

Neat hack. Good.

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PR Review: https://git.openjdk.org/jdk/pull/23296#pullrequestreview-2573183948