Request for review (XS): 6901572 JVM 1.6.16 crash on loops: assert(has_node(i),"")

Vladimir Kozlov Vladimir.Kozlov at Sun.COM
Wed Dec 2 11:40:25 PST 2009


Update the comment in loopnode.cpp for dead phi check.

So we hit the assert in build_loop_late because in
the secondary IV code we added new users of the phi
and set control for them (phase->set_ctrl(add, cl)).
Is this assumption correct? Or it was different reason?


Changpeng Fang wrote:
> Fixes 6901572 JVM 1.6.16 crash on loops: assert(has_node(i),"")
> Problem:
> When the loop optimizer handles secondary induction variables in 
> IdealLoopTree::counted_loop,
> it hits a dead phi and results in "assert(has_node(i),"")" at the time 
> of  "get_ctrl" for the dead node.
> The phi is dead because "final int x" in the attached test case is 
> useless and becomes dead after the
> safepoint is removed for the counted loop.
> Solution:
> Skip the secondary induction variable handling if it is dead. The dead 
> phi will be put into the deadlist
> late in PhaseIdealLoop::build_loop_late and removed.
> Test:
> test case in the bug report.
> Thanks,
> Changpeng

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