8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

[GoeLin]

I backport this for parity with 17.0.8-oracle.

---

Progress

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Issue

• JDK-8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/1300/head:pull/1300
$ git checkout pull/1300

Update a local copy of the PR:
$ git checkout pull/1300
$ git pull https://git.openjdk.org/jdk17u-dev.git pull/1300/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1300

View PR using the GUI difftool:
$ git pr show -t 1300

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk17u-dev/pull/1300.diff

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[bridgekeeper]

👋 Welcome back goetz! 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]

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

[openjdk]

@GoeLin 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:

8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

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[mlbridge]

Webrevs

• 00: Full (d7881fd2)

[GoeLin]

Pre-submit failure: bootjdk download failed. Unrelated.

[GoeLin]

/integrate

[openjdk]

Going to push as commit 241c066.
Since your change was applied there have been 6 commits pushed to the master branch:

• 48632e5: 8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument
• 52324b5: 8300079: SIGSEGV in LibraryCallKit::inline_string_copy due to constant NULL src argument
• ac823d3: 8306664: GHA: Update MSVC version to latest stepping
• da740fa: 8302595: use-after-free related to GraphKit::clone_map
• 790802b: 8293858: Change PKCS7 code to use default SecureRandom impl instead of SHA1PRNG
• 394a756: 8254711: Add java.security.Provider.getService JFR Event

Your commit was automatically rebased without conflicts.

[openjdk]

@GoeLin Pushed as commit 241c066.

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