IV95069: JAVA JIT: INCORRECT ARRAY CONTENTS CAUSED BY AUTO-SIMD

APAR status

• Closed as program error.

Error description

• Error Message: Unexpected Java exception:
  org.apache.lucene.index.CorruptIndexException: Corrupted:
  lengths mismatch: 203 > 72
  .
  Stack Trace: The problem, as reported, occurred while executing
  the JIT compiled method:
  org/apache/lucene/codecs/compressing/CompressingStoredFieldsRead
  er$BlockState.doReset()
  But the problem is not limited to just this method if similar
  Java code exists in other methods they too could trigger the
  issue.
  .
  An unexpected exception is the result we have seen so far, but
  the issue could result in incorrect calculations for array
  elements of most types of arrays except arrays of objects.
  Therefore the symptoms of this problem could be incorrect output
  as well as unexpected exceptions.
  The issue is only possible in Java 8.
  

Local fix

• The problem can be avoided with the following Java command line
  option:
  -Xjit:disableAutoSIMD
  This option will have minimal performance impact for most
  applications. It could have a more noticeable impact for smaller
  applications that have significant opportunities for the
  AutoSIMD optimization to take effect, but this is very rare.
  

Problem summary

• The AutoSIMD optimization should avoid cases where a loop uses
  previous elements of the array in the calculations for
  subsequent array elements, but in this rare case that
  restriction was not effective.
  

Problem conclusion

• The JIT has been modified so that the autoSIMD optimization does
  not act in cases where this error would result.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR4 FP10  (8.0.4.10)
  .
  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

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