8356447: Change default for EagerJVMCI to true

[dougxc]

By default, JVMCI and Graal initialization only occurs on the first top-tier (i.e. tier 4) JIT compilation request. This made sense prior to libgraal where the initialization was interpreted and so noticeably contributed to VM startup. However, with libgraal, the initialization is sufficiently fast to not impact startup.

The motivation for JVMCI and Graal eager initialization by default is to make Graal command line option processing happen in the same VM phase as handling of all other VM command line flags. That is, errors in Graal options should:

1. Happen deterministically, not just for apps that run long enough to trigger a top tier JIT compilation. For example: java -XX:+UnlockExperimentalVMOptions -XX:+UseGraalJIT --version. In a JDK build that does not include Graal, this may succeed (and print out the version info) or result in a VM error ("Cannot use JVMCI compiler: No JVMCI compiler found").
2. Stop the VM before any application code can be executed. This is just good hygiene.

This PR makes JVMCI initialization eager by default if UseJVMCICompiler is true.
This is done for both libgraal and jargraal so that the behavior is uniform. Since jargraal is now a development configuration, VM startup costs are not critical.

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Progress

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Issue

• JDK-8356447: Change default for EagerJVMCI to true (Enhancement - P4)

Reviewers

• Yudi Zheng (@mur47x111 - Committer)
• Vladimir Kozlov (@vnkozlov - Reviewer)
• Tom Rodriguez (@tkrodriguez - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

@dougxc This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8356447: Change default for EagerJVMCI to true

Reviewed-by: yzheng, kvn, never

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 213 new commits pushed to the master branch:

• 0318e49: 8351415: (fs) Path::toAbsolutePath should specify if an absolute path has a root component
• b8c69df: 8356551: Javac rejects receiver parameter in constructor of local class in early construction context
• 64a858c: 8355992: Add unsignedMultiplyExact and *powExact methods to Math and StrictMath
• ... and 210 more: https://git.openjdk.org/jdk/compare/e2ae50d877b13b121912e2496af4b5209b315a05...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

@dougxc The following labels will be automatically applied to this pull request:

• graal
• hotspot-compiler

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[mlbridge]

Webrevs

• 01: Full - Incremental (ad4be5dc)
• 00: Full (42c351b5)

[vnkozlov]

The default value is false - I don't think you need check it.
You can use FLAG_SET_ERGO_IF_DEFAULT(EagerJVMCI, true);

[mur47x111]

LGTM

[vnkozlov]

@dougxc please remind me. Is it true that with current libgraal no Java code is executed when it is initialized? Or you still have calls into core library?

[dougxc]

@dougxc please remind me. Is it true that with current libgraal no Java code is executed when it is initialized? Or you still have calls into core library?

There are still some calls to CompilerToVM.lookupType during libgraal initialization but I think all the types it looks up will already be resolved so will not require Java code execution.

[dougxc]

Thanks for the reviews!

/integrate

[openjdk]

Going to push as commit 08b2df8.
Since your change was applied there have been 213 commits pushed to the master branch:

• 0318e49: 8351415: (fs) Path::toAbsolutePath should specify if an absolute path has a root component
• b8c69df: 8356551: Javac rejects receiver parameter in constructor of local class in early construction context
• 64a858c: 8355992: Add unsignedMultiplyExact and *powExact methods to Math and StrictMath
• ... and 210 more: https://git.openjdk.org/jdk/compare/e2ae50d877b13b121912e2496af4b5209b315a05...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dougxc Pushed as commit 08b2df8.

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