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  1. JDK
  2. JDK-8023472

C2 optimization breaks with G1

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Details

    • Bug
    • Status: Closed
    • P2
    • Resolution: Fixed
    • hs25
    • hs25
    • hotspot
    • b49
    • Not verified

    Backports

      Description

        On the hotspot-dev mailing list on OpenJDK it was reported by Punya Biswal that a small Java program can trigger a crash with hotspot.

        It seems like this is a C2 optimization that goes wrong. For some reason it only seem to happen with G1, so maybe it is related to some thing special that G1 does (the extra write barries?) but it is not a GC bug since the program does not trigger any GCs at all.

        The issue is reported on 7u25, but it exists in the latest JDK8 build too (b103).

        It is likely a C2 issue since running with -Xint or tiered compilation enabled does not cause the crash. Note that since tiered compilation is default in the later JDK8 builds it needs to be explicitly turned off for the reproducer to crash.

        Making this a P2. Motivation:

        Impact: High - crash
        Likelihood: Low - Unsure about this. It seems to be a special case. But with the reproducer it happens every time.
        Workaround: High. Don't know yet if particular tuning can be done. Currently the only workaround is to run with C1.

        ILW=HLH -> P2

        Attachments

          1. G1CrashTest.java
            1 kB
            Bengt Rutisson
          2. hs_err_pid73034.log
            37 kB
            Bengt Rutisson

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                kvn Vladimir Kozlov
                brutisso Bengt Rutisson (Inactive)
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                  Created:
                  Updated:
                  Resolved: