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8288303: C1: Miscompilation due to broken Class.getModifiers intrinsic #8

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shipilev
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@shipilev shipilev commented Jun 13, 2022

Looks like another instance when compilicated control flow in C1 LIR intrinsic confuses the C1 regalloc into miscompiling. Reliably reproduces on selected JFR tests in selected configurations, and I was unable to reproduce it in smaller test.

Additional testing:

  • JFR reproducers now pass
  • Linux x86_64 fastdebug tier1
  • Linux x86_32 fastdebug tier1
  • Linux x86_64 fastdebug tier2
  • Linux x86_32 fastdebug tier2

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  • JDK-8288303: C1: Miscompilation due to broken Class.getModifiers intrinsic

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👋 Welcome back shade! 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 openjdk bot added the rfr Pull request is ready for review label Jun 13, 2022
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@shipilev The following label will be automatically applied to this pull request:

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Webrevs

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openjdk bot commented Jun 13, 2022

@shipilev 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:

8288303: C1: Miscompilation due to broken Class.getModifiers intrinsic

Reviewed-by: iveresov, dlong

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At the time when this comment was updated there had been 2 new commits pushed to the master branch:

  • 53ef59c: 8288365: ProblemList java/lang/reflect/callerCache/ReflectionCallerCacheTest.java in -Xcomp on macosx-x64 and windows-x64
  • 7aafc69: 8288105: [PPC64] Problems with -XX:+VerifyStack

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shipilev commented Jun 13, 2022

Curiously, I deliberately broke the intrinisic in one of my experiments and realized no test caught it! So I added a test for intrinsic as well... The original patch has the test that exercises the canonicalization path, but not the intrinsification path.

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The change looks OK. However, it does seem useful for an intrinsic to be able to use "local" labels that won't confuse the register allocator. That seems better than using a less-efficient cmove or having to write the intrinsic at the LIRAssembler level.

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The change looks OK. However, it does seem useful for an intrinsic to be able to use "local" labels that won't confuse the register allocator. That seems better than using a less-efficient cmove or having to write the intrinsic at the LIRAssembler level.

Yeah, this is not the first time this happens. So I submitted JDK-8288317 yesterday hoping for better diagnostics, at least. Maybe local labels would be nice to have, if they are implementable.

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Thanks for reviews!

/integrate

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openjdk bot commented Jun 14, 2022

Going to push as commit 8cd87e7.
Since your change was applied there have been 3 commits pushed to the master branch:

  • c76a06a: 8288214: serviceability/jvmti/vthread/VThreadNotifyFramePopTest/VThreadNotifyFramePopTest.java test failed
  • 53ef59c: 8288365: ProblemList java/lang/reflect/callerCache/ReflectionCallerCacheTest.java in -Xcomp on macosx-x64 and windows-x64
  • 7aafc69: 8288105: [PPC64] Problems with -XX:+VerifyStack

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Jun 14, 2022
@openjdk openjdk bot closed this Jun 14, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 14, 2022
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openjdk bot commented Jun 14, 2022

@shipilev Pushed as commit 8cd87e7.

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

@shipilev shipilev deleted the JDK-8288303-c1-class-getmodifiers branch June 22, 2022 17:05
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