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IV07699: JAVA JIT PPC - RARE INCORRECT CALCULATION

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • Error Message: An unexpected ArrayIndexOutOfBoundsException was
    thrown for the customer who reported this problem, but the
    problem is a incorrect calculation which can result in other
    symptoms depending on how the incorrect value is used.
    .
    Stack Trace: N/A
    .
    The problem only effects PowerPC (AIX32/64 and LinuxPPC32/64) on
    Java5, Java6 and Java6.0.1.
    

Local fix

  • The problem can be avoided by excluding the compilation of the
    method that performs the incorrect calculation. If that method
    is known then the following java command line option can be used
    to avoid the problem:
    -Xjit:exclude={Package/Class.method*}
    Note: Excluding a method can degrade performance depending on
    how the excluded method is used by the application. In a typical
    application, excluding one methods has almost no effect on
    performance.
    

Problem summary

  • When a 'left shift' (or power of 2 multiply) is performed along
    with an 'and' operation we can use the PowerPC 'rlwimn'
    instruction. This works for most cases, but if the 'and' bit
    mask as no bits set to 1, the instruction does not work as you
    might expect resulting an the 'and' operation not being
    performed as expected.
    

Problem conclusion

  • This defect will be fixed in:
    6.0.1 SR2
    6.0.0 SR10
    5.0.0 SR13
    .
    The JIT was modified to use a different instruction when doing a
    'shift' and an 'and' with a mask of 0.
    .
    To obtain the fix:
    Install build 20110921 or later
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV07699

  • Reported component name

    JAVA 5 JIT

  • Reported component ID

    620500124

  • Reported release

    500

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-09-16

  • Closed date

    2011-10-28

  • Last modified date

    2011-10-28

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

    IV07698

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

Fix information

  • Fixed component name

    JAVA 5 JIT

  • Fixed component ID

    620500124

Applicable component levels

  • R500 PSY

       UP

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Document Information

Modified date:
28 October 2011