8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure

[satyenme]

Backporting JDK-8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure. Addresses failure found when running compiler/loopopts/TestVerifyLoopOptimizations.java test with Shenandoah GC. Fix replaces CountedLoop with a Loop node when a load barrier is expanded on the backedge of the counted loop. Adds test to confirm expected behavior. Ran GHA Sanity Checks, local Tier 1 and 2 tests. Patch is clean.

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Progress

• Change must not contain extraneous whitespace
• JDK-8328107 needs maintainer approval
• Commit message must refer to an issue

Issue

• JDK-8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure (Bug - P3 - Approved)

Reviewing

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[bridgekeeper]

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

[openjdk]

@satyenme This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure

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At the time when this comment was updated there had been 84 new commits pushed to the master branch:

• 28cb19e: 8136895: Writer not closed with disk full error, file resource leaked
• 2439c6d: 8349637: Integer.numberOfLeadingZeros outputs incorrectly in certain cases
• bc441e3: 8353709: Debug symbols bundle should contain full debug files when building --with-external-symbols-in-bundles=public
• ... and 81 more: https://git.openjdk.org/jdk21u-dev/compare/89b614d99790efe07b2fb31c33fe5560d3dc2850...master

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[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @satyenme This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[mlbridge]

Webrevs

• 00: Full (f0fa88dc)

[satyenme]

/approval request for backport. Fix replaces CountedLoop with a Loop node when a load barrier is expanded on the backedge of the counted loop.

Risk: Low. Change should only address breaking case, and adds test to confirm functionality. Only affects Shenandoah. Change was merged in June 2024 in tip.

Testing:

• GHA Sanity Checks
• Tier 1 and 2 tests locally

[openjdk]

@satyenme
8328107: The approval request has been created successfully.