8259984: IGV: Crash when drawing control flow before GCM

[robcasloz]

The block formation algorithm applied by IGV to schedule graphs without associated CFG information traverses the graph backwards. This makes it difficult to deal with block projection nodes, leading in some cases to double addition of block nodes and block edges, and ultimately causing assertion failures.

This fix replaces the backward traversal by a forward traversal that relies on node category information (introduced in 8261336) to identify control successors. The forward traversal is arguably simpler and, besides avoiding the reported assertion failure, has two advantages:

• it places block projection nodes in the same block as their predecessors, and
• it numbers basic blocks more naturally.

The following screenshots illustrate the improvements (before the fix to the left, after the fix to the right):

Tested automatically on tens of thousands of graphs by running java -Xcomp -XX:-TieredCompilation -XX:PrintIdealGraphLevel=4 ... on an instrumented version of IGV that schedules graphs eagerly. Checked manually that the CFGs of a few selected graphs (included the reported one) are well-formed. Also checked that the overall IGV graph scheduling time is not affected by the changes.

Thanks to Christian Hagedorn for checking the fix independently.

---

Progress

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Issue

• JDK-8259984: IGV: Crash when drawing control flow before GCM

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer)
• Nils Eliasson (@neliasso - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2607/head:pull/2607
$ git checkout pull/2607

[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (9f6444b)
• 00: Full (6998772)

[chhagedorn]

Looks good to me! I played around with it in the IGV. I regularly got some assertion failure messages before - now they are gone now 👍

[openjdk]

@robcasloz 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:

8259984: IGV: Crash when drawing control flow before GCM

Replace backward traversal in the IGV block formation algorithm by forward
traversal guided by node category information. This change addresses the
reported assertion failures, places block projection nodes together with their
predecessors, and gives a more natural block numbering.

Reviewed-by: chagedorn, 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 45 new commits pushed to the master branch:

• 7e2c909: 8260485: Simplify and unify handler vectors in Posix signal code
• c99eeb0: 8260858: Implementation specific property xsltcIsStandalone for XSLTC Serializer
• 5caf686: 8261644: NMT: Simplifications and cleanups
• ed93bc9: 8196301: java/awt/print/PrinterJob/Margins.java times out
• 7e78c77: 8261905: Move implementation of OopStorage num_dead related functions
• 78cde64: 8261860: Crash caused by lambda proxy class loaded in Shutdown hook
• c158413: 8261098: Add clhsdb "findsym" command
• 0c31d5b: 8261977: Fix comment for getPrefixed() in canonicalize_md.c
• 9cf4f90: 8261473: Shenandoah: Add breakpoint support
• c4664e6: 8261940: Fix references to IOException in BigDecimal javadoc
• ... and 35 more: https://git.openjdk.java.net/jdk/compare/16bd7d381f498ed659d2b1b372458d86fbbef275...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.

[neliasso]

Excellent!

[robcasloz]

Thanks Christian and Nils for reviewing! Christian, I refactored the code as per your suggestion, please have a look again.

[chhagedorn]

Looks good!

[robcasloz]

/summary
Replace backward traversal in the IGV block formation algorithm by forward
traversal guided by node category information. This change addresses the
reported assertion failures, places block projection nodes together with their
predecessors, and gives a more natural block numbering.

[openjdk]

@robcasloz Setting summary to:

Replace backward traversal in the IGV block formation algorithm by forward
traversal guided by node category information. This change addresses the
reported assertion failures, places block projection nodes together with their
predecessors, and gives a more natural block numbering.

[robcasloz]

Looks good!

Thanks again, Christian.

[robcasloz]

/integrate

[openjdk]

@robcasloz Since your change was applied there have been 45 commits pushed to the master branch:

• 7e2c909: 8260485: Simplify and unify handler vectors in Posix signal code
• c99eeb0: 8260858: Implementation specific property xsltcIsStandalone for XSLTC Serializer
• 5caf686: 8261644: NMT: Simplifications and cleanups
• ed93bc9: 8196301: java/awt/print/PrinterJob/Margins.java times out
• 7e78c77: 8261905: Move implementation of OopStorage num_dead related functions
• 78cde64: 8261860: Crash caused by lambda proxy class loaded in Shutdown hook
• c158413: 8261098: Add clhsdb "findsym" command
• 0c31d5b: 8261977: Fix comment for getPrefixed() in canonicalize_md.c
• 9cf4f90: 8261473: Shenandoah: Add breakpoint support
• c4664e6: 8261940: Fix references to IOException in BigDecimal javadoc
• ... and 35 more: https://git.openjdk.java.net/jdk/compare/16bd7d381f498ed659d2b1b372458d86fbbef275...master

Your commit was automatically rebased without conflicts.

Pushed as commit 61820b7.

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