IV19965: JVM INCORRECTLY REMOVED A CONDITION CHECK WHEN COMPARING TO MIN OR MAX INTEGER

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APAR status

  • Closed as program error.

Error description

  • Error Message: The Java JIT compiler might remove a comparison
    of an integer variable by mistake if it dominates (or is
    dominated by) a comparison of the same integer variable
    against the minimum or maximum integer value. This leads to
    incorrect control flow in the program and could result in a
    variety of associated symptoms such as segmentation fault,
    incorrect output, or hang.
    .
    Stack Trace: N/A
    .
    The following Java code illustrates the problem:
    
    if (i <= 0x7fffffff)  // always true
      {
      if (i < 0)          // sometimes removed by the JIT
        System.out.print("input < 0");
      }
    else
      System.out.print("should never get here");
    
    When the JIT compiler malfunctions in this case, it could remove
    the (i < 0) check, and cause the program to always print "input
    < 0" even if the variable i is positive.
    

Local fix

  • The -Xjit:disableAndSimplification option can be used as a
    workaround. Note that a small performance degradation might
    occur as this disables some compiler optimizations.
    

Problem summary

  • The problem is caused by an incorrect overflow/underflow check
    in the Java  JIT compiler.
    

Problem conclusion

  • This defect will be fixed in:
    6.0.1 SR2
    7.0.0 SR1
    .
    The JIT compiler has been updated to resolve the problem
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV19965

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    260

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-04-20

  • Closed date

    2012-04-20

  • Last modified date

    2013-04-15

  • 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



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Document information


More support for:

Runtimes for Java Technology
Just In Time (JIT) Compiler

Software version:

260

Reference #:

IV19965

Modified date:

2013-04-15

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