RFR (S) 8247296: Optimize JVM_GetDeclaringClass

[Yumin Qi]

Hi, David

On 7/23/20 11:44 PM, David Holmes wrote:
>
> I must stress I am sponsoring Christoph's change and only extended it 
> within the current file. :) I'm sure there are many, many more 
> opportunities for similar optimisations. Though you have to be careful 
> to ensure you don't expose an unhandled oop.
>
>> 1) 
>> https://github.com/openjdk/jdk/blob/master/src/hotspot/share/compiler/compileBroker.cpp#L834 
>>
>>     Where thread_handle resolved multiple times.
>
> True that is unnecessary, but this is a compiler code and I'd need to 
> extend the review so ... I'll pass on this one.
>
That is OK.
>> 2) 
>> https://github.com/openjdk/jdk/blob/master/src/hotspot/share/prims/jni.cpp#L1174 
>>
>>      Where clazz resolved twice.
>
> Fixed this as it is the same pattern in a core runtime file. Webrev 
> updated in place.
>
Looks good!


Thanks

Yumin

> Thanks,
> David
>
>
>
>>      Do you want to include those two files in your list?
>>
>> Thanks
>>
>> Yumin
>>
>> On 7/23/20 8:49 PM, David Holmes wrote:
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8247296
>>> webrev: http://cr.openjdk.java.net/~dholmes/8247296/webrev/
>>>
>>> Please review this simple optimization contributed by Christoph 
>>> Dreis in its initial form and then expanded by me to cover other 
>>> cases in jvm.cpp.
>>>
>>> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2020-June/040025.html 
>>>
>>>
>>> There is a common pattern of code of the form:
>>>
>>> if 
>>> (java_lang_Class::is_primitive(JNIHandles::resolve_non_null(ofClass)) 
>>> ||
>>>     ! 
>>> java_lang_Class::as_Klass(JNIHandles::resolve_non_null(ofClass))->is_instance_klass()) 
>>> {
>>>
>>> which resolves cls twice. There are also duplicate calls to as_Klass 
>>> that can be removed in a couple of cases.
>>>
>>> Testing: tiers 1 - 3
>>>
>>> Thanks,
>>> David