8352897: RISC-V: Change default value for UseConservativeFence

[robehn]

Hi, please consider.

gcc have stopped emitting io-bits for fences since 13.
And we need to use newer gcc due to other compiler bugs.
Therefore there is no point in letting JIT emit io-bits when the runtime don't have them.

Thanks, Robbin

---

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Issue

• JDK-8352897: RISC-V: Change default value for UseConservativeFence (Enhancement - P4)

Reviewers

• Ludovic Henry (@luhenry - Committer)
• Fei Yang (@RealFYang - Reviewer)

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[openjdk]

@robehn 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:

8352897: RISC-V: Change default value for UseConservativeFence

Reviewed-by: luhenry, fyang

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 22 new commits pushed to the master branch:

• a81250c: 8352673: RISC-V: Vector can't be turned on with -XX:+UseRVV
• 0935ba9: 8352481: Enforce the use of lld with clang
• dbc620f: 8352299: GenShen: Young cycles that interrupt old cycles cannot be cancelled
• f5a0db4: 8315447: Invalid Type Annotation attached to a method instead of a lambda
• 60544a1: 8164714: Constructor.newInstance creates instance of inner class with null outer class
• c856b34: 8352587: C2 SuperWord: we must avoid Multiversioning for PeelMainPost loops
• 993eae4: 8346948: Update CLDR to Version 47.0
• e98838f: 8352065: [PPC64] C2: Implement PopCountVL, CountLeadingZerosV and CountTrailingZerosV nodes
• 03105fc: 8351601: [JMH] test UnixSocketChannelReadWrite failed for 2 threads config
• fe03e2e: 8351897: Extra closing curly brace typos in Javadoc
• ... and 12 more: https://git.openjdk.org/jdk/compare/6879c446c6e7734c162c85bd2bd3d7f3b012cca4...master

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]

@robehn The following label will be automatically applied to this pull request:

• hotspot-compiler

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[mlbridge]

Webrevs

• 00: Full (0b5c3f37)

[robehn]

Thank you @luhenry !

[RealFYang]

Looks good.

[robehn]

Thanks @RealFYang!

[robehn]

/integrate

[openjdk]

Going to push as commit 1007811.
Since your change was applied there have been 46 commits pushed to the master branch:

• 7853415: 8352218: RISC-V: Zvfh requires RVV
• 2483340: 8352579: Refactor CDS legacy optimization for lambda proxy classes
• 1397ee5: 8334322: Misleading values of keys in jpackage resource bundle
• 441bd12: 8352812: remove useless class and function parameter in SuspendThread impl
• e83cccf: 8352948: Remove leftover runtime_x86_32.cpp after 32-bit x86 removal
• 5672a93: 8348400: GenShen: assert(ShenandoahHeap::heap()->is_full_gc_in_progress() || (used_regions_size() <= _max_capacity)) failed: Cannot use more than capacity #
• c2a4fed: 8348907: Stress times out when is executed with ZGC
• 5392674: 8352766: Problemlist hotspot tier1 tests requiring tools that are not included in static JDK
• 1d205f5: 8352716: (tz) Update Timezone Data to 2025b
• a2a64da: 8352588: GenShen: Enabling JFR asserts when getting GCId
• ... and 36 more: https://git.openjdk.org/jdk/compare/6879c446c6e7734c162c85bd2bd3d7f3b012cca4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@robehn Pushed as commit 1007811.

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