8266615: C2 incorrectly folds subtype checks involving an interface array

[TobiHartmann]

C2 incorrectly folds the subtype checks in TestInterfaceArraySubtypeCheck::test1/test2. As a result, an unexpected ClassCastException is thrown at checkcast and instanceof returns a wrong result. The problem is in Compile::static_subtype_check where we incorrectly return SSC_always_false for the MyInterface[] <: MyClassA[] check because MyClassA[] is not a subtype of MyInterface[] (after checking that MyInterface[] is not a subtype of MyClassA[]).

The fix is to check that subelem is not an interface. This is very old code and not a recent regression.

Thanks,
Tobias

---

Progress

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Issue

• JDK-8266615: C2 incorrectly folds subtype checks involving an interface array

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Nils Eliasson (@neliasso - Reviewer)

Reviewing

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• 00: Full (cc88c112)

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@TobiHartmann 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:

8266615: C2 incorrectly folds subtype checks involving an interface array

Reviewed-by: kvn, neliasso

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 20 new commits pushed to the master branch:

• 894547d: 8266897: com/sun/net/httpserver/FilterTest.java fails intermittently with AssertionError
• da7c846: 8264408: test_oopStorage no longer needs to disable some tests on WIN32
• f6c2891: 8267229: Split runtime/Metaspace/elastic test configurations for better scalability
• b60975d: 8267237: ARM32: bad AD file in matcher.cpp after 8266810
• 905b41a: 8265711: C1: Intrinsify Class.getModifier method
• 554caf3: 8251392: Consolidate Metaspace Statistics
• 3e97b07: 8267116: Lanai: Incorrect AlphaComposite for VolatileImage graphics
• cd1c17c: 8266404: Fatal error report generated with -XX:+CrashOnOutOfMemoryError should not contain suggestion to submit a bug report
• 2effdd1: 8267112: JVMCI compiler modules should be kept upgradable
• da4dfde: 8264777: Overload optimized FileInputStream::readAllBytes
• ... and 10 more: https://git.openjdk.java.net/jdk/compare/a555fd89d040792d4de73ab67d86b171a38cfde6...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.

[TobiHartmann]

Thanks for the review, Vladimir!

[neliasso]

Looks good.

[TobiHartmann]

Thanks Nils!

[TobiHartmann]

/integrate

[openjdk]

@TobiHartmann Since your change was applied there have been 20 commits pushed to the master branch:

• 894547d: 8266897: com/sun/net/httpserver/FilterTest.java fails intermittently with AssertionError
• da7c846: 8264408: test_oopStorage no longer needs to disable some tests on WIN32
• f6c2891: 8267229: Split runtime/Metaspace/elastic test configurations for better scalability
• b60975d: 8267237: ARM32: bad AD file in matcher.cpp after 8266810
• 905b41a: 8265711: C1: Intrinsify Class.getModifier method
• 554caf3: 8251392: Consolidate Metaspace Statistics
• 3e97b07: 8267116: Lanai: Incorrect AlphaComposite for VolatileImage graphics
• cd1c17c: 8266404: Fatal error report generated with -XX:+CrashOnOutOfMemoryError should not contain suggestion to submit a bug report
• 2effdd1: 8267112: JVMCI compiler modules should be kept upgradable
• da4dfde: 8264777: Overload optimized FileInputStream::readAllBytes
• ... and 10 more: https://git.openjdk.java.net/jdk/compare/a555fd89d040792d4de73ab67d86b171a38cfde6...master

Your commit was automatically rebased without conflicts.

Pushed as commit ce88b33.

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