IJ25133: JAVA JIT: INCORRECT INSTRUCTION USED LOADING 16BIT ARRAY ELEMENTS UNDER BALANCED GC POLICY

APAR status

• Closed as program error.

Error description

• Error Message: Incorrect UTF-8 conversions when using
  -Xgcpolicy:balanced with input data more then 256000bytes and
  double byte characters
  .
  Stack Trace: N/A
  .
  The problem can only occur when using the balanced GC policy and
  only when running on zSeries hardware (zOS & zLinux). It also
  requires that the input data results in a large array (more the
  256kb of text data with minimum heap sizes, more for larger
  heaps). The problem could occur with any 16bit data types in
  large arrays as long at it's on zSeries and using the balanced
  GC policy.
  

Local fix

• The problem can only be avoided by using a GC policy other then
  balanced (i.e. the default policy gencon).
  

Problem summary

• The JIT might use an incorrect instruction for loading a 16bit
  value from memory which would perform a sign extend into the
  upper 16bits of the lower 32bits of a register.
  

Problem conclusion

• The JIT was modified so that it uses the correct instruction
  when loading 16bit values.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR6 FP11  (8.0.6.11)
  .
  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