8346475: RISC-V: Small improvement for MacroAssembler::ctzc_bit

[RealFYang]

Hi, please review this small improvement.

When step is 16, the andi instruction in the loop performs a bitwise AND with immediate mask value 0xFFFF. This will emit 3 instructions. It's effectively a zero extension operation and could be reduced to 1 or 2 instructions repectively depending on whether Zbb extension is available. And there is no difference when step is 8 with this change.

Testing: tier1 and gtest:all are clean on Premier-P550 SBC running Ubuntu-24.04.

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Issue

• JDK-8346475: RISC-V: Small improvement for MacroAssembler::ctzc_bit (Enhancement - P4)

Reviewers

• Hamlin Li (@Hamlin-Li - Reviewer)
• Feilong Jiang (@feilongjiang - Committer) Review applies to f4d9b181

Reviewing

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[bridgekeeper]

👋 Welcome back fyang! 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]

@RealFYang 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:

8346475: RISC-V: Small improvement for MacroAssembler::ctzc_bit

Reviewed-by: mli, fjiang

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 10 new commits pushed to the master branch:

• a0b7c4f: 8346324: javax/swing/JScrollBar/4865918/bug4865918.java fails in CI
• 8efc558: 8346378: Cannot use DllMain in libnet for static builds
• 73b5dba: 8345655: Move reservation code out of ReservedSpace
• d50b725: 8344647: Make java.se participate in the preview language feature requires transitive java.base
• 9e8aa85: 8346017: Socket.connect specified to throw UHE for unresolved address is problematic for SOCKS V5 proxy
• 5b703c7: 8342782: AWTEventMulticaster throws StackOverflowError using AquaButtonUI
• edbd76c: 8344951: Stabilize write barrier micro-benchmarks
• 842f801: 8339331: GCC fortify error in vm_version_linux_aarch64.cpp
• 4533109: 8345911: Enhance error message when IncompatibleClassChangeError is thrown for sealed class loading failures
• ea50c54: 8321818: vmTestbase/nsk/stress/strace/strace015.java failed with 'Cannot read the array length because "" is null'

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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[openjdk]

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[mlbridge]

Webrevs

• 02: Full - Incremental (714f2b94)
• 01: Full - Incremental (f4d9b181)
• 00: Full (1f86156b)

[Hamlin-Li]

Looks good. Thanks!

[Hamlin-Li]

Sorry, just realize this.

[Hamlin-Li]

Another comment.

[feilongjiang]

Looks good, thanks!

[Hamlin-Li]

Looks good, thanks for updating!

[RealFYang]

@Hamlin-Li @feilongjiang : Thanks for the review! Tier1-2 test is still clean with the latest version. Moving on.
/integrate

[openjdk]

Going to push as commit 6b89954.
Since your change was applied there have been 15 commits pushed to the master branch:

• 00d8407: 8346016: Problemlist vm/mlvm/indy/func/jvmti/mergeCP_indy2manyDiff_a in virtual thread mode
• 5db0a13: 8346132: fallbacklinker.c failed compilation due to unused variable
• 5590669: 8346570: SM cleanup of tests for Beans and Serialization
• c8e94ab: 8346532: XXXVector::rearrangeTemplate misses null check
• f7f2b42: 8346300: Add @test annotation to TCKZoneId.test_constant_OLD_IDS_POST_2024b test
• a0b7c4f: 8346324: javax/swing/JScrollBar/4865918/bug4865918.java fails in CI
• 8efc558: 8346378: Cannot use DllMain in libnet for static builds
• 73b5dba: 8345655: Move reservation code out of ReservedSpace
• d50b725: 8344647: Make java.se participate in the preview language feature requires transitive java.base
• 9e8aa85: 8346017: Socket.connect specified to throw UHE for unresolved address is problematic for SOCKS V5 proxy
• ... and 5 more: https://git.openjdk.org/jdk/compare/c0f0b8e5f4d83ae7dd7e67930c19134855e5e97b...master

Your commit was automatically rebased without conflicts.

[openjdk]

@RealFYang Pushed as commit 6b89954.

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