IJ15187: DIVISION BY CERTAIN CONSTANTS IS OPTIMIZED INCORRECTLY ON BIG-ENDIAN POWER

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  Performing 64-bit division of non-constant values by the
  constants 12884901888 (0x300000000), 21474836480 (0x500000000),
  30064771072 (0x700000000), 38654705664 (0x900000000),
  42949672960 (0xa00000000), or 51539607552 (0xc00000000) on
  big-endian Power machines may return incorrect results in JITted
  methods. This affects both Linux and AIX on big-endian Power
  running Java 8. This issue does not affect Java 7 or prior, nor
  does it affect little-endian Power or any other architectures.
  

Local fix

• N/A
  

Problem summary

• During optimization on certain architectures, division of
  non-constant values by known constants is optimized into a
  multiplication by a magic value to avoid long-latency division
  instructions. The function for doing this was returning
  incorrect magic values for certain large denominators due to an
  endianness bug that would result in an internal table being read
  with the two words of a 64-bit integer reversed.
  

Problem conclusion

• The optimizer has been fixed to return the correct magic values
  for all denominators regardless of the endianness of the
  machine.
  .
  This APAR will be fixed in the following Java Releases:
   8 SR5 FP35 (8.0.5.35)
  .
  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