8341275: Explicit counter support for Code attribute building

[liach]

Internal explicit counter support for Code max_stack and max_locals has been already added in #24807. Since that example works well, we may consider opening this functionality up to general users under strict restrictions.

This is an advanced API; thus, I chose a more complex name withExplicitStackAndLocals that discourages accidental use, and indicates the exact order of stack and locals arguments. For integrity, the argument checks are unconditional. And this is also barred behind DROP_STACK_MAPS advanced option.

I have enhanced the tests with a CodeBuilderType utility to test all types of code builders; it is already effective at increasing coverage in some of our existing tests that only cover DirectCodeBuilder, and simplify other tests. It is particularly helpful for my new BuilderExplicitMaxsTest.

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Progress

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Issues

• JDK-8341275: Explicit counter support for Code attribute building (Enhancement - P4)
• JDK-8355653: Explicit counter support for Code attribute building (CSR) (Withdrawn)

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[bridgekeeper]

👋 Welcome back liach! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (989a494a)
• 00: Full (e60e3e07)

[liach]

Testing: tier 1-3

[asotona]

Stack counter already serves to very limited set of use cases.
In a hunt for the maximum JDK performance #24705 called specific implementation method and saved some CPU cycles by setting explicit maxLocals and maxStack in the SwitchBootstraps.
However I'm not sure this single corner case of the corner cases is enough to make it a public API.

[liach]

I think the original issue was created in response to a public request https://mail.openjdk.org/pipermail/classfile-api-dev/2024-August/000545.html. It just happens that we and another public audience both want this API, so I guess it is not too much of a "corner case"?

[liach]

Thanks, withdrawing this for now. A better approach may be to optimize StackCounter when a SMT is present.