[13] RFR(S): 8218201: Failures when vmIntrinsics::_getClass is not inlined

[Tobias Hartmann]

Thanks Vladimir and Dean.

Best regards,
Tobias

On 08.03.19 20:22, dean.long at oracle.com wrote:
> +1
> 
> dl
> 
> On 3/8/19 10:29 AM, Vladimir Kozlov wrote:
>> Looks good.
>>
>> Thanks,
>> Vladimir
>>
>> On 3/8/19 12:25 AM, Tobias Hartmann wrote:
>>> Vladimir, Dean, thanks for the review.
>>>
>>> My first fix version had '_return_allocated = false' but then I incorrectly assumed that the
>>> behavior would be the same as if we don't special case at all. I missed that the receiver is of
>>> course also involved and you are right that we should not treat it as "global escape".
>>>
>>> New webrev:
>>> http://cr.openjdk.java.net/~thartmann/8218201/webrev.01/
>>>
>>> Best regards,
>>> Tobias
>>>
>>> On 07.03.19 20:20, dean.long at oracle.com wrote:
>>>> I agree.  We don't want obj.getClass() to treat obj as "global escape".
>>>>
>>>> dl
>>>>
>>>> PS - Original change goes back to JDK-6488063.
>>>>
>>>> On 3/7/19 10:46 AM, Vladimir Kozlov wrote:
>>>>> _getClass is special case because it is native call and we can't do bytecode analysis.
>>>>> But we know what it does (it loads klass from object and mirror from klass) - no allocations, no
>>>>> locals, no arguments returned.
>>>>> I think it is simple missing _return_allocated = false setting in addition to _return_local =
>>>>> false. _return_allocated is set to true by default optimistically.
>>>>>
>>>>> Thanks,
>>>>> Vladimir
>>>>>
>>>>> On 3/7/19 4:54 AM, Tobias Hartmann wrote:
>>>>>> Hi,
>>>>>>
>>>>>> please review the following patch:
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8218201
>>>>>> http://cr.openjdk.java.net/~thartmann/8218201/webrev.00/
>>>>>>
>>>>>> When intrinsification is disabled, the BCEscapeAnalyzer marks the return value of the (native)
>>>>>> method Object::getClass as "return allocated value" which means that "only newly allocated
>>>>>> unescaped
>>>>>> objects are returned". The OptimizePtrCompare optimization then uses this information to
>>>>>> incorrectly
>>>>>> fold 'obj.getClass() == Object.class' (see TestGetClass.java:39) to always false.
>>>>>>
>>>>>> This is a very old issue and I can't trace back why a special case for the _getClass intrinsic
>>>>>> has
>>>>>> been added to the BCEscapeAnalyzer. Since I don't think we should make any assumptions about the
>>>>>> returned Object, I've removed the special case.
>>>>>>
>>>>>> Thanks,
>>>>>> Tobias
>>>>>>
>>>>
>