Request for reviews (S): 7190310: Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops

[Vladimir Kozlov]

Thank you, Christian

Vladimir

Christian Thalinger wrote:
> On Aug 15, 2012, at 4:26 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
> 
>> I updated webrev:
>>
>> http://cr.openjdk.java.net/~kvn/7190310/webrev.01
>>
>> During testing I found several problem with code for unsafe.getObject() intrinsic code in both: C1 and C2. I moved some checks in C1 from G1UnsafeGetObjSATBBarrierStub stub into shared code and also added static klass analysis to avoid generation of G1/membar code if klass is not Reference or Object. In C2 I hit bad graph problem because If node's projections in insert_pre_barrier() were not put on IGVN worklist.
>>
>> I added jtreg tests (thanks to John Cuthbertson for unsafe test which I extended).
>>
>> Tested with CTW and Kitchensink with C1, C2, tiered.
> 
> Looks good.
> 
> -- Chris
> 
>> Thanks,
>> Vladimir
>>
>> Vladimir Kozlov wrote:
>>> Christian Thalinger wrote:
>>>> On Aug 9, 2012, at 7:15 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>>>
>>>>> Thanks, David
>>>>>
>>>>> pre_barrier() methods don't generate code for other GCs. But I forgot to put UseG1GC guard around "new G1UnsafeGetObjSATBBarrierStub" in c1_LIRGenerator.cpp.
>>>> Did you update the webrev?  -- Chris
>>> Not yet. I want to rewrite that code (which use G1UnsafeGetObjSATBBarrierStub).
>>> Vladimir
>>>>> Thanks,
>>>>> Vladimir
>>>>>
>>>>> On 8/9/12 6:52 PM, David Holmes wrote:
>>>>>> On 10/08/2012 11:34 AM, Vladimir Kozlov wrote:
>>>>>>> http://cr.openjdk.java.net/~kvn/7190310/webrev
>>>>>>>
>>>>>>> 7190310: Inlining WeakReference.get(), and hoisting $referent may lead
>>>>>>> to non-terminating loops
>>>>>>>
>>>>>>> Add acquire membar after load from Reference.referent field to prevent
>>>>>>> commoning of loads across safepoint since GC can change its value.
>>>>>> Wow that was quick! :)
>>>>>>
>>>>>> My only comment (not being a compiler expert) is that it would appear that we are now inserting read barriers with all
>>>>>> GC's not just G1. What kind of impact will that have on performance under the other GC's?
>>>>>>
>>>>>> Thanks,
>>>>>> David
>>>>>>
>>>>>>> Thanks,
>>>>>>> Vladimir
>