IV14086: JAVA METHOD MISBEHAVES WHEN JIT-COMPILED

APAR status

• Closed as program error.

Error description

• Error Message: When a Java method with unusual characteristics
  has been JIT-compiled, it may produce incorrect I/O, cause an
  ABEND or unexpected exception, or crash.
  .
  Stack Trace: N/A
  .
  This issue will most likely affect a Java method with a
  combination of branches, method calls, loops, and unusual
  definitions and uses of loop induction variables.
  

Local fix

• This issue can be avoided using the -Xjit:disableGlobalVP
  option. Note that this option prevents the JIT compiler from
  performing many types of optimization. This will cause a
  significant impact on performance.
  

Problem summary

• The problem is caused when the JIT compiler performs an
  optimization known as value propagation, and mistakenly
  concludes that a definition of a variable is unreachable code.
  As a result, it propagates an incorrect alternative definition
  of the variable to a use later on in the method, causing
  unexpected behaviour.
  

Problem conclusion

• This defect will be fixed in:
  6.0.0 SR11
  6.0.1 SR2
  7.0.0 SR1
  .
  The JIT compiler has been updated to prevent the incorrect
  propagation.
  

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:

  PM57142

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R600 PSY

     UP

• R260 PSY

     UP