[9] RFR (XXS): 8062258: compiler/debug/TraceIterativeGVN.java segfaults in trace_PhaseIterGVN

[Vladimir Kozlov]

Hmm, next code in PhaseIterGVN::optimize() worries me. We dump dead 
nodes before removing them from graph:

     DEBUG_ONLY(trace_PhaseIterGVN_verbose(n, num_processed++);)
     if (n->outcnt() != 0) {
       NOT_PRODUCT(const Type* oldtype = type_or_null(n));
       // Do the transformation
       Node* nn = transform_old(n);
       NOT_PRODUCT(trace_PhaseIterGVN(n, nn, oldtype);)
     } else if (!n->is_top()) {
       remove_dead_node(n);
     }

I am changing my suggestion: fix  Node::dump() which calls  adr_type() 
without check. It should not call MemNode::dump_adr_type() because 
MemNode::dump_spec(), which is called before, already does that and it 
has NULL check! If you want, you can add "  Memory:" output in 
MemNode::dump_spec() to be similar to Node::dump() output.

Thanks,
Vladimir

On 10/30/14 10:26 AM, Vladimir Ivanov wrote:
> Vladimir, do you suggest to simply skip printing info about dead nodes
> w/ -XX:+TraceIterativeGVN?
>
> Best regards,
> Vladimir Ivanov
>
> On 10/29/14, 7:00 PM, Vladimir Kozlov wrote:
>> I would suggest to dead node check in trace_PhaseIterGVN() instead of
>> in  MemNode::adr_type().
>> So the fix for your JDK-8061995 should fix this problem too.
>>
>> Thanks,
>> Vladimir
>>
>> On 10/29/14 4:57 AM, Vladimir Ivanov wrote:
>>> http://cr.openjdk.java.net/~vlivanov/8062258/webrev.00/
>>> https://bugs.openjdk.java.net/browse/JDK-8062258
>>>
>>> Trivial fix to avoid NULL dereference w/ -XX:+TraceIterativeGVN while
>>> querying adr_type() on dead MemNode.
>>>
>>> Testing: failing test.
>>>
>>> Best regards,
>>> Vladimir Ivanov