[8] RFR (XS): 8031695: CHA ignores default methods during analysis leading to incorrect code generation

[Lois Foltan]

On 1/22/2014 3:34 PM, Vladimir Ivanov wrote:
> John, Karen, thanks for review!
>
> Special thanks goes to Lois for initial analysis and instructions how 
> to reproduce the issue. It saved me lots of time.

Hi Vladimir,
Thanks, your change looks good and as I mentioned earlier I tried it 
with the test case and all is fine.  I would also be remiss not to point 
out that Christian Tornqvist also was very helpful in diagnosing key 
aspects about this problem.  Thanks Christian!
Lois

>
> Best regards,
> Vladimir Ivanov
>
> On 1/22/14 11:16 PM, Karen Kinnear wrote:
>> Looks good.
>>
>> many thanks,
>> Karen
>>
>> On Jan 22, 2014, at 12:29 PM, Vladimir Ivanov wrote:
>>
>>> http://cr.openjdk.java.net/~vlivanov/8031695/webrev.00/
>>> https://bugs.openjdk.java.net/browse/JDK-8031695
>>>
>>> CHA erroneously ignores default methods when looking for different 
>>> versions of a method in a class hierarchy.
>>>
>>> Consider the following hierarchy:
>>>   interface I { default void m() { ... }}
>>>   class A implements I {}
>>>
>>>   class C extends A { }
>>>   class D extends A { public void m() { ... } }
>>>
>>> Call site: invokevirtual A.m()
>>>
>>> A.m resolves to I.m. Searching from A, CHA finds only D.m and 
>>> concludes that D.m is the only implementation of I.m, since 
>>> Dependencies::is_concrete_method returns false for I.m.
>>>
>>> But there is C with default implementation from I. So, if VM inlines 
>>> D.m and then C's instance is passed as objectref, the wrong method 
>>> is invoked (D.m instead of I.m).
>>>
>>> The fix is to take default methods into account doing CHA analysis 
>>> and treat the call site as non-monomorphic when a concrete method is 
>>> found for a default method.
>>>
>>> Conservative approach is chosen, since the fix is targeted for 8.
>>>
>>> Testing: failing application, regression test, vm.defmeth.testlist, 
>>> JDK regression tests (java/util/, java/lang)
>>>
>>> Thanks!
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>