8260653: Unreachable nodes keep speculative types alive

[neliasso]

The RunThese test fails because after first igvn.optimize() (directly after parsing) there are unreachable nodes cycles left. Later when remove_speculative_types() is called - only reachable nodes will have their speculative type removed. At the end of remove_speculative_types() there is an assert that all speculative types have been removed that will fail.

This problem will not cause crashes in production - it is only a sanity test.

I suggest adding a call to PhaseRemoveUseless before remove_speculative_types. This will cost a few extra cycles but it is the only way we can guarantee that no unreachable nodes are left.

When debugging this I experimented with adding a call to verify_graph_edges to check for dead code at the same spot. This triggers failures in a lot of test. The conclusion is that it is very common that we have dead node cycles - but they very rarely keep speculative types alive.

A big thank you to Dean Long how created the reproducer for this bug.

Please review.

---

Progress

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Issue

• JDK-8260653: Unreachable nodes keep speculative types alive

Reviewers

• Vladimir Ivanov (@iwanowww - Reviewer) ⚠️ Review applies to 82ab106
• Tobias Hartmann (@TobiHartmann - Reviewer) ⚠️ Review applies to ac23dad

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2606/head:pull/2606
$ git checkout pull/2606

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Webrevs

• 03: Full - Incremental (ae048cb)
• 02: Full - Incremental (ac23dad)
• 01: Full - Incremental (82ab106)
• 00: Full (5f27917)

[neliasso]

One reasonable alternative to adding one more pass of PhaseRemoveUseless is filtering out all non-reachable nodes from NodeHash::check_no_speculative_types. The unreachable nodes only live a short while before being removed in the renumbering phase.

[iwanowww]

Looks good.

[openjdk]

@neliasso 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:

8260653: Unreachable nodes keep speculative types alive

Reviewed-by: vlivanov, thartmann

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 15 new commits pushed to the master branch:

• b695c7e: 8261925: ProblemList com/sun/jdi/AfterThreadDeathTest.java on Linux
• 97e1657: 8261846: [JVMCI] c2v_iterateFrames can get out of sync with the StackFrameStream
• b8fd614: 8261939: os::strdup_check_oom() should be used in os::same_files() in os_windows.cpp
• 5f30829: 8202750: Reduce the use of get_canonical_path() in CDS
• ea5bf45: 8261621: Delegate Unicode history from JLS to j.l.Character
• d5a4d22: 8261843: incorrect info in docs/building.html
• bf75a3a: 8261851: update ReflectionCallerCacheTest.java test to use ForceGC from test library
• 05301f5: 8257497: Update keytool to create AKID from the SKID of the issuing certificate as specified by RFC 5280
• cb84539: 8261553: Efficient mask generation using BMI2 BZHI instruction
• a065879: 8261791: (sctp) handleSendFailed in SctpChannelImpl.c potential leaks
• ... and 5 more: https://git.openjdk.java.net/jdk/compare/03b586b32cc1c471f2c7d60122b866bb71554a4a...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]

Otherwise looks good.

[neliasso]

Thanks for the reviews Vladimir and Tobias!

[neliasso]

/integrate

[openjdk]

@neliasso Since your change was applied there have been 15 commits pushed to the master branch:

• b695c7e: 8261925: ProblemList com/sun/jdi/AfterThreadDeathTest.java on Linux
• 97e1657: 8261846: [JVMCI] c2v_iterateFrames can get out of sync with the StackFrameStream
• b8fd614: 8261939: os::strdup_check_oom() should be used in os::same_files() in os_windows.cpp
• 5f30829: 8202750: Reduce the use of get_canonical_path() in CDS
• ea5bf45: 8261621: Delegate Unicode history from JLS to j.l.Character
• d5a4d22: 8261843: incorrect info in docs/building.html
• bf75a3a: 8261851: update ReflectionCallerCacheTest.java test to use ForceGC from test library
• 05301f5: 8257497: Update keytool to create AKID from the SKID of the issuing certificate as specified by RFC 5280
• cb84539: 8261553: Efficient mask generation using BMI2 BZHI instruction
• a065879: 8261791: (sctp) handleSendFailed in SctpChannelImpl.c potential leaks
• ... and 5 more: https://git.openjdk.java.net/jdk/compare/03b586b32cc1c471f2c7d60122b866bb71554a4a...master

Your commit was automatically rebased without conflicts.

Pushed as commit 3a21e1d.

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