IV72266: INCORRECT BEHAVIOUR IN JAVA PROGRAM WHEN A LOOP IS OPTIMIZED

APAR status

• Closed as program error.

Error description

• Error Message: A loop induction variable or loop counter
  variable contains an incorrect value after the loop has finished
  execution, which could lead to incorrect behaviour or unexpected
  exceptions. The problem can potentially affect code that
  iterates through a byte or character array and accesses an item
  in a form of <OSB>index + offset<CSB>, where index is an
  induction variable and is used outside of the loop afterwards.
  .
  Stack Trace: N/A
  .
  This problem is only triggered on System z (both z/OS and
  Linux).
  

Local fix

• This problem can be avoided by setting the JVM option
  -Xjit:{full method name}(disableIdiomRecognition) for the method
  that is causing the issue. This may cause some performance
  degradation.
  

Problem summary

• The problem is caused by the idiom recognition optimization in
  the JIT compiler which did not handle offsets added to induction
  variables within a loop properly.
  

Problem conclusion

• The JIT compiler has been modified to fix this error.
  .
  This APAR will be fixed in the following Java Releases:
     7    SR9       (7.0.9.0)
     7 R1 SR3       (7.1.3.0)
     6    SR16 FP4  (6.0.16.4)
     6 R1 SR8 FP4   (6.1.8.4)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• 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

• R130 PSY

     UP

• R260 PSY

     UP

• R600 PSY

     UP