8271459: C2: Missing NegativeArraySizeException when creating StringBuilder with negative capacity

[chhagedorn]

Stringopts does not take into account that a negative int argument for StringBuilder(int) results in a NegativeArraySizeException when optimizing away StringBuilder usages into single strings.

The suggested fix does the following:

• Bailout of Stringopts if C2 knows that an int argument is always negative.
• Apply stringopts but insert an additional runtime check with an UCT if C2 cannot tell if an int argument is positive or negative.

I added some IR tests to verify the fix and also ran some standard benchmarks.

I also updated TestIRMatching to test the new and updated default regexes.

Thanks,
Christian

---

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Issue

• JDK-8271459: C2: Missing NegativeArraySizeException when creating StringBuilder with negative capacity

Reviewers

• Roland Westrelin (@rwestrel - Reviewer) ⚠️ Review applies to ab8b6f8
• Tobias Hartmann (@TobiHartmann - Reviewer)
• Nils Eliasson (@neliasso - Reviewer)

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[bridgekeeper]

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[mlbridge]

Webrevs

• 01: Full - Incremental (4e4f5222)
• 00: Full (ab8b6f8a)

[rwestrel]

Looks reasonable to me.

[openjdk]

@chhagedorn 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:

8271459: C2: Missing NegativeArraySizeException when creating StringBuilder with negative capacity

Reviewed-by: roland, thartmann, neliasso

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At the time when this comment was updated there had been 208 new commits pushed to the master branch:

• 2e690ba: 8274322: Problems with oopDesc construction
• a8edd1b: 8274527: Minimal VM build fails after JDK-8273459
• 7326481: 8274393: Suppress more warnings on non-serializable non-transient instance fields in security libs
• 8215b2e: 8274398: Suppress more warnings on non-serializable non-transient instance fields in management libs
• 9573022: 8253197: vmTestbase/nsk/jvmti/StopThread/stopthrd007/TestDescription.java fails with "ERROR: DebuggeeSleepingThread: ThreadDeath lost"
• f08180f: 8274501: c2i entry barriers read int as long on AArch64
• c57ed22: 8274528: Add comment to explain an HKDF optimization in SSLSecretDerivation
• 9180d9a: 8273216: JCMD does not work across container boundaries with Podman
• 3e0d7c3: 8270290: NTLM authentication fails if HEAD request is used
• bfd6163: 8274196: Crashes in VM_HeapDumper::work after JDK-8252842
• ... and 198 more: https://git.openjdk.java.net/jdk/compare/4c673df31e46644b21fefa51e0ea01f7d9b94856...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.

[chhagedorn]

Thanks Roland for your review!

[neliasso]

If we hit the uncommontrap - should we recompile without applying strconcat? Or is this code so uncommon that we don't want to add complexity for that case?

[chhagedorn]

I guess we could do that by changing the UCT from Action_none to Action_maybe_recompile. I pushed an update.

[TobiHartmann]

That looks good to me given that we check for too_many_traps in StringConcat::validate_control_flow().

[chhagedorn]

Thanks for your review Tobias! Right, that should prevent the application of stringopts again.

[neliasso]

Looks good!

[chhagedorn]

Thanks Nils for your review!

[chhagedorn]

/integrate

[openjdk]

Going to push as commit 3953e07.
Since your change was applied there have been 236 commits pushed to the master branch:

• 53d7e95: 8274635: Use String.equals instead of String.compareTo in jdk.accessibility
• e43f540: 8274651: Possible race in FontDesignMetrics.KeyReference.dispose
• 2e542e3: 8274349: ForkJoinPool.commonPool() does not work with 1 CPU
• 7e757f6: 8274559: JFR: Typo in 'jfr help configure' text
• 75d6688: 8274745: ProblemList TestSnippetTag.java
• 9914e5c: 8274610: Add linux-aarch64 to bootcycle build profiles
• 0ca094b: 8273244: Improve diagnostic output related to ErroneousTree
• 6f727d8: 8274666: rename HtmlStyle.descfrmTypeLabel to be less cryptic
• 139a833: 8268869: java in source-file mode suggests javac-only Xlint flags
• f63c4a8: 8274471: Verification of OCSP Response signed with RSASSA-PSS fails
• ... and 226 more: https://git.openjdk.java.net/jdk/compare/4c673df31e46644b21fefa51e0ea01f7d9b94856...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn Pushed as commit 3953e07.

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