IJ04251: JIT COMPILED METHOD THAT TAKES ADVANTAGE OF AUTOSIMD PRODUCES AN INCORRECT RESULT ON X86

APAR status

• Closed as program error.

Error description

• Error Message: At one point in a Java test run on x86 there is a
  check to see if a produced result matches an expected result.
  The produced result does not match and the following error is
  displayed:
  java.lang.RuntimeException:
  Expecting ###, but actual ###
  The two ### are different numbers.
  .
  Stack Trace: N/A
  .
  

Local fix

• -Xjit:disableAutoSIMD
  This option will disable the AutoSIMD optimization that leads to
  the problematic behavior.
  

Problem summary

• The AutoSIMD optimization triggers a problem in the assignment
  of XMM registers. This leads to incorrect generation of code
  which then leads to producing an incorrect result.
  

Problem conclusion

• The JVM was updated such that parts of the AutoSIMD optimization
  were disabled and related parts of the optimizations around
  assigning XMM registers were also disabled.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR5 FP10  (8.0.5.10)
  .
  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