IZ80785: JAVA6 JIT: INCORRECTLY CONVERTING A LOOP INTO A SYSTEM,ARRAYCOPY()

APAR status

• Closed as program error.

Error description

• Error Message: A crash (SIGSEV) while executing JIT compiled
  code was reported by the customer, but other symptoms are
  possible including incorrect behavior, and unexpected
  exceptions.
  .
  Stack Trace: N/A
  .
  The problem can only occur in Java6, Java5 does not have the
  optimization that caused this problem. The problem can occur in
  Java6 on any platform and architecture.
  

Local fix

• The problem can be avoided by using the following Java command
  line option:
  -Xjit:disableIdiomRecognition
  This option may have a slight impact on the performance of the
  Java application. In a typical application the performance
  difference will not be noticeable.
  

Problem summary

• The JIT would incorrectly detect a code pattern that it believed
  could be replaced with a call to System.arraycopy(). After
  replacing the loop with an arraycopy() call the code would no
  longer behave as it was intended.
  

Problem conclusion

• This defect will be fixed in:
  6.0.0 SR10
  .
  The JIT was modified to address this problem.
  .
  To obtain the fix:
  Install build 20100730 or later
  

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

• R600 PSN

     UP