8320280: RISC-V: Avoid passing t0 as temp register to MacroAssembler::lightweight_lock/unlock

[zifeihan]

Clean backport which fixes a potential risk for passing t0 as temporary register to MacroAssembler::lightweight_lock/unlock. This is a riscv-specific change, risk is low.

Testing:

• Run tier1-3 tests with qemu 8.1.50 (default locking mode) (release)
• Run non-trivial benchmark workloads (specjbb2005, dacapo, renaissance) with -XX:LockingMode=2 (fastdebug & release)

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8320280 needs maintainer approval

Issue

• JDK-8320280: RISC-V: Avoid passing t0 as temp register to MacroAssembler::lightweight_lock/unlock (Enhancement - P4 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u.git pull/399/head:pull/399
$ git checkout pull/399

Update a local copy of the PR:
$ git checkout pull/399
$ git pull https://git.openjdk.org/jdk21u.git pull/399/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 399

View PR using the GUI difftool:
$ git pr show -t 399

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u/pull/399.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back gcao! 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]

⚠️ @zifeihan 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 (84c21b00)

[openjdk]

@zifeihan 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:

8320280: RISC-V: Avoid passing t0 as temp register to MacroAssembler::lightweight_lock/unlock

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 1 new commit pushed to the master branch:

• ecb199a: 8313616: support loading library members on AIX in os::dll_load

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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change.

➡️ 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).

[zifeihan]

/integrate

[RealFYang]

/sponsor

[openjdk]

@zifeihan
Your change (at version 84c21b0) is now ready to be sponsored by a Committer.

[openjdk]

Going to push as commit 3df010f.
Since your change was applied there has been 1 commit pushed to the master branch:

• ecb199a: 8313616: support loading library members on AIX in os::dll_load

Your commit was automatically rebased without conflicts.

[openjdk]

@RealFYang @zifeihan Pushed as commit 3df010f.

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