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8367244: [lworld] C2 compilation fails with assert "no node with a side effect" #1716

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8367244: [lworld] C2 compilation fails with assert "no node with a side effect" #1716

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@mhaessig mhaessig commented Nov 3, 2025 •
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Problem Analysis

The stress test compiler/valhalla/inlinetypes/TestAcmpWithUnstableIf.java, which uses the StressUnstableIfTrap flag, failed intermittently with the assert "no node with a side effect" during C2 compilation. I tracked down the origin of the failure to the raw store of the unstable if trap stress counter that was missing a memory edge to the backedge phi and thus had no side effect in the loop, which lead to the aforementioned assert. During parsing, the missing memory edge gets discarded with as vestigial parsing state when do_if() ends up stopped(). However, the effect of the stress counter should still be wired back into the backedge since it will be incremented in the next iteration.

Patch Description

To prevent the stress counters memory state being lost to PreserveJVMState, I pass it to the caller over an out-parameter and set_memory with that node, similar to what is already done for control. This is only necessary for the two last invocation of do_if() in do_acmp() where they are actually allowed to trap. Further, this PR reenables StressUnstableIfTrap in compiler/valhalla/inlinetypes/TestAcmpWithUnstableIf.java.

Testing

  • tier1,tier2,tier3 plus internal stress testing

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  • Change must not contain extraneous whitespace

Issue

  • JDK-8367244: [lworld] C2 compilation fails with assert "no node with a side effect" (Bug - P4)

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bridgekeeper bot commented Nov 3, 2025

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

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openjdk bot commented Nov 3, 2025 •
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@mhaessig 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:

8367244: [lworld] C2 compilation fails with assert "no node with a side effect"

Reviewed-by: chagedorn

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@mhaessig mhaessig marked this pull request as ready for review November 3, 2025 14:30
@openjdk openjdk bot added ready Pull request is ready to be integrated rfr Pull request is ready for review labels Nov 3, 2025
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chhagedorn
chhagedorn approved these changes Nov 5, 2025
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Looks reasonable to me, thanks for fixing this!

test/hotspot/jtreg/compiler/valhalla/inlinetypes/TestAcmpStressUnstableIf.java Outdated
* compiler.valhalla.inlinetypes.TestAcmpStressUnstableIf
* @run main/othervm -Xbatch -XX:-TieredCompilation
* -XX:CompileCommand=compileonly,compiler/valhalla/inlinetypes/TestAcmpStressUnstableIf.test
* -XX:+UnlockDiagnosticVMOptions -XX:+StressUnstableIfTraps -XX:RepeatCompilation=100
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Given that the test will be run over and over again, I think we can remove RepeatCompilation to improve test execution time.

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mhaessig commented Nov 6, 2025

Thank you for having a look, @chhagedorn. I removed the repeated compilation.

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mhaessig commented Nov 6, 2025

/integrate

@openjdk openjdk bot added the sponsor Pull request is ready to be sponsored label Nov 6, 2025
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openjdk bot commented Nov 6, 2025

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Your change (at version 9e09aa2) is now ready to be sponsored by a Committer.

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chhagedorn commented Nov 7, 2025

/sponsor

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openjdk bot commented Nov 7, 2025

Going to push as commit a0ec244.
Since your change was applied there have been 104 commits pushed to the lworld branch:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Nov 7, 2025
@openjdk openjdk bot closed this Nov 7, 2025
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Nov 7, 2025
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@chhagedorn @mhaessig Pushed as commit a0ec244.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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@chhagedorn chhagedorn chhagedorn approved these changes

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