JDK-8136461 : PhaseIdealLoop::try_move_store_before_loop() may bypass early loop exit
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 9
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2015-09-14
  • Updated: 2015-11-12
  • Resolved: 2015-09-16
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JDK 9
9 b89Fixed
Related Reports
Relates :  
JDK-8080289 - Intermediate writes in a loop not eliminated by optimizer
Description
In some cases, a Store that is moved out of loop by a try_move_store_before_loop(), is input to a MergeMem that itself is input to a bottom memory Phi for the loop. The loop has an exit point before the Store. That exit point uses the bottom memory Phi as memory state. Moving the Store out of loop shouldn't be attempted in that case.
Comments
regarding lack of test case: I tried reproducing the steps that lead to the graph shape that triggers this bug but couldn't in a simple test case
16-09-2015
ILW=H(incorrect execution)L(seen only a few times with CTW)H(none)=P2
14-09-2015