8308084: C2 fix idom bug in PhaseIdealLoop::create_new_if_for_predicate

[eme64]

Bug fixing to make the verification pass for #13951 JDK-8305073.

There only seemed to be one bug with idom that I could find up to tier6 and stress testing. That one bug already showed up with a simple java -Xcomp --version. But it is possible that there are more that we would find in the future, maybe with the fuzzer.

Details about the bug I fixed in PhaseIdealLoop::create_new_if_for_predicate:
We computed the dom_lca_internal for rgn too early - the following line can change the CFG such that the idom would change:

jdk/src/hotspot/share/opto/loopPredicate.cpp

Line 216 in 1e1abc4

set_idom(iff, if_cont, dom_depth(iff));

So I moved the idom computation down, until after we do not change the CFG anymore, and idom should be stable from there on.

---

Progress

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Issue

• JDK-8308084: C2 fix idom bug in PhaseIdealLoop::create_new_if_for_predicate

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer) ⚠️ Review applies to db4e7e46
• Tobias Hartmann (@TobiHartmann - Reviewer) ⚠️ Review applies to db4e7e46
• Vladimir Kozlov (@vnkozlov - Reviewer)

Reviewing

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$ git checkout pull/13980

Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/13980/head

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Checkout this PR locally:
$ git pr checkout 13980

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[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full (015d9f3d)
• 00: Full (db4e7e46)

[chhagedorn]

Looks good!

[openjdk]

@eme64 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:

8308084: C2 fix idom bug in PhaseIdealLoop::create_new_if_for_predicate

Reviewed-by: chagedorn, thartmann, kvn

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 6 new commits pushed to the master branch:

• f57c783: 8308239: Tighten up accessibility of nested classes in java.lang.invoke
• 64f6681: 8308246: PPC64le build broken after JDK-8304913
• 5763be7: 8307326: Package jdk.internal.classfile.java.lang.constant become obsolete
• c7951cf: 8306304: Fix xlc17 clang warnings in ppc and aix code
• 285c833: 8308043: Deadlock in TestCSLocker.java due to blocking GC while allocating
• 1a6f981: 8308185: Update Http2TestServerConnection to use SSLSocket.startHandshake()

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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.

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[TobiHartmann]

Looks good to me.

[openjdk]

@eme64 this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout JDK-8308084
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[eme64]

@vnkozlov @TobiHartmann @chhagedorn Thanks for the reviews!
/integrate

[openjdk]

Going to push as commit 41beb44.
Since your change was applied there have been 50 commits pushed to the master branch:

• b6a9f5c: 8307619: C2 failed: Not monotonic (AndI CastII LShiftI) in TestShiftCastAndNotification.java
• eaa80ad: 8300543: Compiler Implementation for Pattern Matching for switch
• 5ccc962: 8308342: Remove MetaspaceClosure::Ref::keep_after_pushing()
• a0f4a94: 8307783: runtime/reflect/ReflectOutOfMemoryError.java timed out
• 939344b: 8304685: Fix whitespace parsing in libjdwp
• 241455f: 8307962: Exclude gc/g1/TestSkipRebuildRemsetPhase.java fails with virtual test thread factory
• 34468e1: 8308021: Update IANA Language Subtag Registry to Version 2023-05-11
• f0aebc8: 8305972: Update XML Security for Java to 3.0.2
• 265f40b: 8308396: Fix offset_of conversion warnings in runtime code
• a5343fa: 8281149: (fs) java/nio/file/FileStore/Basic.java fails with java.lang.RuntimeException: values differ by more than 1GB
• ... and 40 more: https://git.openjdk.org/jdk/compare/b300e73a4acb5c64f68a355e0ad70d3862084ff4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@eme64 Pushed as commit 41beb44.

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