8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations

[rm-gh-8]

Backporting JDK-8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations. Adds several tests for string concatenation optimization in C2. Ran GHA Sanity Checks (passed) and adjusted tests (passed). Patch is clean.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8357822 needs maintainer approval

Issue

• JDK-8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations (Bug - P4 - Approved)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/4130/head:pull/4130
$ git checkout pull/4130

Update a local copy of the PR:
$ git checkout pull/4130
$ git pull https://git.openjdk.org/jdk17u-dev.git pull/4130/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4130

View PR using the GUI difftool:
$ git pr show -t 4130

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk17u-dev/pull/4130.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

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[openjdk]

@rm-gh-8 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:

8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations

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 3 new commits pushed to the master branch:

• 9449e0b: 8369450: [Ubuntu 25.10] openjdk fails to build due to rust-coreutils date
• 9dbee30: 8325766: Extend CertificateBuilder to create trust and end entity certificates programmatically
• 7fe2553: 8369226: GHA: Switch to MacOS 15

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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➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

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

[rm-gh-8]

/covered

[rm-gh-8]

/signed

[bridgekeeper]

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[openjdk]

⚠️ @rm-gh-8 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

• 01: Full - Incremental (afcf43c2)
• 00: Full (8935e9f1)

[rm-gh-8]

Merged in order to pull in GHA Sanity Check fix.

[rm-gh-8]

/approval request for backport of JDK-8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations.

Ran the updated tests as well as related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

(All Passed) - make test TEST=hotspot/jtreg/compiler
(All Passed) - make test TEST=hotspot/jtreg/vmTestbase/vm/compiler/optimizations/stringconcat/implicit

Results are attached.

windows-x64-hotspot-vmtestbase-vm-compiler-optimizations-stringconcat-implicit.log
windows-x64-hotspot-compiler.log
linux-x64-hotspot-vmtestbase-vm-compiler-optimizations-stringconcat-implicit.log
linux-x64-hotspot-compiler.log
linux-aarch64-hotspot-vmtestbase-vm-compiler-optimizations-stringconcat-implicit.log
linux-aarch64-hotspot-compiler.log
macos-aarch64-hotspot-vmtestbase-vm-compiler-optimizations-stringconcat-implicit.log
macos-aarch64-hotspot-compiler.log

[openjdk]

@rm-gh-8
8357822: The approval request has been created successfully.

[shipilev]

/sponsor

[openjdk]

@shipilev The change author (@rm-gh-8) must issue an integrate command before the integration can be sponsored.

[rm-gh-8]

/integrate

[openjdk]

@rm-gh-8
Your change (at version afcf43c) is now ready to be sponsored by a Committer.

[Rudometov]

/sponsor

[openjdk]

Going to push as commit 943251d.
Since your change was applied there have been 3 commits pushed to the master branch:

• 9449e0b: 8369450: [Ubuntu 25.10] openjdk fails to build due to rust-coreutils date
• 9dbee30: 8325766: Extend CertificateBuilder to create trust and end entity certificates programmatically
• 7fe2553: 8369226: GHA: Switch to MacOS 15

Your commit was automatically rebased without conflicts.

[openjdk]

@Rudometov @rm-gh-8 Pushed as commit 943251d.

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