JDK-8196294 : LoopStripMiningIterShortLoop is set to zero by default
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 10,11
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-01-26
  • Updated: 2019-09-13
  • Resolved: 2018-03-21
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JDK 11
11 b07Fixed
Related Reports
Relates :  
JDK-8186027 - C2: loop strip mining
Description
LoopStripMiningIterShortLoop is supposed to be set to LoopStripMiningIter / 10 by default but the initializing code is never executed:

java -XX:+PrintFlagsFinal -version | grep LoopStripMiningIter
    uintx LoopStripMiningIter                      = 1000                                  {C2 product} {default}
    uintx LoopStripMiningIterShortLoop             = 0                                     {C2 product} {default}

java -XX:+PrintFlagsFinal -XX:LoopStripMiningIterShortLoop=100 -version | grep LoopStripMiningIter
    uintx LoopStripMiningIter                      = 1000                                  {C2 product} {default}
    uintx LoopStripMiningIterShortLoop             = 100                                   {C2 product} {command line}
Comments
ILW = Flag is set to wrong default value affecting C2 loop strip mining optimization, with G1 (default), set explicitly via -XX:LoopStripMiningIterShortLoop = MHL = P3
26-01-2018