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IV68132: JAVA JIT - MERGING BOUND-CHECKS CAN PREVENT CODE FROM BEING EXEC UTED.

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APAR status

  • Closed as program error.

Error description

  • Error Message: Unexpected behaviour when executing catch blocks
    handling IndexOutOfBoundsException.
    .
    Stack Trace: N/A
    .
    The problem could occur on all platforms and all releases of the
    J9 VM, but given that it only effects IndexOutOfBoundsException
    exception paths, it's very unlikely to be encountered.
    

Local fix

  • -Xjit:disableAndSimplificationNote: Use of this option will have
    a very small effect on the performance of some JIT generated
    code. The over all effect of a applications performance will be
    less then 1% in almost all cases.
    

Problem summary

  • Two near by bound-checks are merged allowing for code that
    should have been executed to be skipped when the exception path
    is taken. The side-effects of this skipped code could only be
    used in the catcher, all other side effects would be spotted and
    prevent the bound-checks from being merged in the first place.
    

Problem conclusion

  • The JIT was modified such that bound-check merging is prevented
    when there is code between the two bound-checks that would
    modify variables used in the exception path.
    .
    This APAR will be fixed in the following Java Releases:
       7    SR9       (7.0.9.0)
       6    SR17      (6.0.17.0)
       6 R1 SR9       (6.1.9.0)
       7 R1 SR3       (7.1.3.0)
       8    SR1       (8.0.1.0)
    .
    Contact your IBM Product's Service Team for these Service
    Refreshes and Fix Packs.
    For those running stand-alone, information about the Service
    Refreshes and Fix Packs can be found at:
               https://www.ibm.com/developerworks/java/jdk/
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV68132

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    260

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2014-12-22

  • Closed date

    2014-12-22

  • Last modified date

    2015-03-09

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    JIT

  • Fixed component ID

    620700124

Applicable component levels

  • R260 PSY

       UP

  • R600 PSY

       UP

  • R130 PSY

       UP

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Document Information

Modified date:
09 March 2015