Request for review (XS): 6901572 JVM 1.6.16 crash on loops: assert(has_node(i),"")
Vladimir.Kozlov at Sun.COM
Wed Dec 2 12:13:42 PST 2009
Changpeng Fang wrote:
> On 12/02/09 11:40, Vladimir Kozlov wrote:
>> Update the comment in loopnode.cpp for dead phi check.
> //Look for other phis (secondary IVs). Skip dead ones.
> Is this ok?
>> 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?
> No, we hit the assert in counted_loop when we set_early_ctrl:
> Node* diff = new (C, 3) SubINode(init2, ratio_init);
> phase->_igvn.register_new_node_with_optimizer(diff, init2);
> phase->set_early_ctrl(diff); // <--- will lead to assert
> The direct reason is that init2 is dead, where:
> Node *init2 = phi2->in( LoopNode::EntryControl );
> But if phi2 (secondary IV) is not dead, init2 should not be dead.
> So, I simply filter out a broader case where the secondary IV is
>> Changpeng Fang wrote:
>>> Fixes 6901572 JVM 1.6.16 crash on loops: assert(has_node(i),"")
>>> When the loop optimizer handles secondary induction variables in
>>> 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.
>>> 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 case in the bug report.
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