IJ15121: JIT: STRING PEEPHOLES OPTIMIZATION FAILURE TO REMOVE CODE CORRECTLY

APAR status

• Closed as program error.

Error description

• Error Message: SIG_SEGV/GPF
  .
  Stack Trace: N/A
  .
  The problem will likely surface as a crash in JIT generated code
  or in the Garbage Collector, but other possibilities exist
  including memory corruption and incorrect behaviour.
  

Local fix

• The problem can be avoided by using the following java command
  line option:
  -Xjit:disableStringPeepholes
  This option will have a small effect on performance. Likely a
  few percent.
  

Problem summary

• The String Peepholes optimization might fail to remove a memory
  barrier operation which could result in a stale object reference
  in a register after a GC cycle. A stale reference will cause
  issues when the reference is used after the GC cycle is over.
  

Problem conclusion

• The JIT was modified so that the String Peepholes optimization
  properly removes unused memory barriers.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR5 FP35  (8.0.5.35)
     7 R1 SR4 FP45  (7.1.4.45)
     7    SR10 FP45 (7.0.10.45)
  .
  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