8360271: String.indexOf intrinsics fail with +EnableX86ECoreOpts and -CompactStrings

[shipilev]

Same as for JDK 26, fixes the regression in JDK 24.

Techinically not clean because there is a conflict in copyright line years, resolved in favor of incoming changeset.

Additional testing:

• Linux x86_64 server fastdebug, new test case fails without the patch, passes with it
• Linux x86_64 server fastdebug, tier1 with -XX:-CompactStrings

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• JDK-8360271 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8360271: String.indexOf intrinsics fail with +EnableX86ECoreOpts and -CompactStrings (Bug - P2 - Requested)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/165/head:pull/165
$ git checkout pull/165

Update a local copy of the PR:
$ git checkout pull/165
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/165/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 165

View PR using the GUI difftool:
$ git pr show -t 165

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/165.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

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

[mlbridge]

Webrevs

• 00: Full (241825d1)

[shipilev]

/approval request Same as for JDK 26, fixes the regression in JDK 24. Applies semi-cleanly (copyright year conflict, needs quick review, see RFR). New subtest catches fire without the fix, works with the fix. Other tests pass. Risk is on lower side: affects platforms with +EnableX86ECoreOpts enabled; we have already seen real-world cases due to this bug.

[openjdk]

@shipilev
8360271: The approval request has been created successfully.