8272720: Fix the implementation of loop unrolling heuristic with LoopPercentProfileLimit

[DamonFool]

Hi all,

I'd like to fix the implementation of loop unrolling heuristic with LoopPercentProfileLimit.

The range of LoopPercentProfileLimit was designed as [10, 100] [1].
But in fact there is no difference when LoopPercentProfileLimit > 50 for the current implementation.

This is because integer div 100 / LoopPercentProfileLimit [2] will always return 1 when LoopPercentProfileLimit > 50.
It would be better to fix it.

Thanks.
Best regards,
Jie

[1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/c2_globals.hpp#L179
[2] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/loopTransform.cpp#L908

---

Progress

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Issue

• JDK-8272720: Fix the implementation of loop unrolling heuristic with LoopPercentProfileLimit

Reviewers

• Tobias Hartmann (@TobiHartmann - Reviewer)
• Rickard Bäckman (@rickard - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

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

• hotspot-compiler

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[mlbridge]

Webrevs

• 00: Full (8d246295)

[TobiHartmann]

Looks good to me.

[openjdk]

@DamonFool 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:

8272720: Fix the implementation of loop unrolling heuristic with LoopPercentProfileLimit

Reviewed-by: thartmann, rbackman

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 9 new commits pushed to the master branch:

• a81e5e9: 8272654: Mark word accesses should not use Access API
• 4bd37c3: 8272708: [Test]: Cleanup: test/jdk/security/infra/java/security/cert/CertPathValidator/certification/BuypassCA.java no longer needs ocspEnabled
• ddcd851: 8272602: [macos] not all KEY_PRESSED events sent when control modifier is used
• d007be0: 8272700: [macos] Build failure with Xcode 13.0 after JDK-8264848
• f4be211: 8270041: Consolidate oopDesc::cas_forward_to() and oopDesc::forward_to_atomic()
• b40e8f0: 8271951: Consolidate preserved marks overflow stack in SerialGC
• 7eccbd4: 8266519: Cleanup resolve() leftovers from BarrierSet et al
• 9569159: 8272674: Logging missing keytab file in Krb5LoginModule
• 51c1b9a: 8272616: Strange code in java.text.DecimalFormat#applyPattern

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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[DamonFool]

Thanks @TobiHartmann and @rickard .
/integrate

[openjdk]

Going to push as commit 1ea437a.
Since your change was applied there have been 15 commits pushed to the master branch:

• 86add21: 8223923: C2: Missing interference with mismatched unsafe accesses
• c701f6e: 8272739: Misformatted error message in EventHandlerCreator
• fb1dfc6: 8267185: Add string deduplication support to ParallelGC
• d874e96: 8271579: G1: Move copy before CAS in do_copy_to_survivor_space
• 92bde67: 8271946: Cleanup leftovers in Space and subclasses
• db9834f: 8258951: java/net/httpclient/HandshakeFailureTest.java failed with "RuntimeException: Not found expected SSLHandshakeException in java.io.IOException"
• a81e5e9: 8272654: Mark word accesses should not use Access API
• 4bd37c3: 8272708: [Test]: Cleanup: test/jdk/security/infra/java/security/cert/CertPathValidator/certification/BuypassCA.java no longer needs ocspEnabled
• ddcd851: 8272602: [macos] not all KEY_PRESSED events sent when control modifier is used
• d007be0: 8272700: [macos] Build failure with Xcode 13.0 after JDK-8264848
• ... and 5 more: https://git.openjdk.java.net/jdk/compare/03b5e99d998e037f84e9e2395b49321979c0acd8...master

Your commit was automatically rebased without conflicts.

[openjdk]

@DamonFool Pushed as commit 1ea437a.

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