IJ05529: JAVA JIT: INCORECT RESULT FROM INSTANCEOF ON MULTI-DIMENSIONAL ARRAYS

APAR status

• Closed as program error.

Error description

• Error Message: Incorrect code path was executed after a
  conditional statement using "instanceof" with "object
  <OSB><CSB><OSB><CSB>" as the right hand side of the operation.
  .
  Stack Trace: N/A
  .
  The problem occurred only with Java 8 SR5 or later and can only
  happen on PowerPC and zSeries machines (AIX / zOS / LinuxPPC /
  zLinux). The issue does not occur on X86.
  The problem can only occur when the right hand side type is a
  subclass of the left hand side object and both sides are arrays
  of 2 or more dimensions.
  

Local fix

• The problem can only be avoided by preventing the method with
  the instanceof check from being JIT compiled:
  i.e.
  -Xjit:exclude={package/class.method*},dontinline={package/class.
  method*}
  

Problem summary

• The JIT would generate an insufficient number of checks for an
  instanceof when the right hand side type is a 2 or more
  dimension array type (i.e. Object <OSB><CSB><OSB><CSB>).
  

Problem conclusion

• The JIT was modified to emit the correct checks for instanceof
  instructions involving multi-dimension arrays.
  .
  This APAR will be fixed in the following Java Releases:
   8 SR5 FP15 (8.0.5.15)
  .
  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:

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels