RFR (XL) 8155672: Remove instanceKlassHandles and KlassHandles

Mikael Gerdin mikael.gerdin at oracle.com
Mon Mar 13 16:11:36 UTC 2017 

Hi Coleen,

On 2017-03-13 17:09, coleen.phillimore at oracle.com wrote:
> Hi Mikael,
>
> On 3/13/17 11:21 AM, Mikael Gerdin wrote:
>> Hi Coleen,
>>
>> On 2017-03-13 13:37, coleen.phillimore at oracle.com wrote:
>>>
>>> David, I'm so sorry, I should have pointed to
>>>
>>> open webrev at http://cr.openjdk.java.net/~coleenp/8155672.02/webrev
>>
>> There are still a bunch of *Klass methods which are static and have an
>> InstanceKlass* (which used to be a handle) as their first parameter.
>> Do you want to leave that to a future cleanup or fold it into this
>> change?
>>
>> Example:
>> 1309   // Static methods that are used to implement member methods
>> where an exposed this pointer
>> 1310   // is needed due to possible GCs
>> 1311   static bool link_class_impl (instanceKlassHandle this_k, bool
>> throw_verifyerror, TRAPS);
>> 1312   static bool verify_code (instanceKlassHandle this_k, bool
>> throw_verifyerror, TRAPS);
>> 1313   static void initialize_impl (instanceKlassHandle this_k, TRAPS);
>> 1314   static void initialize_super_interfaces (instanceKlassHandle
>> this_k, TRAPS);
>> 1315   static void eager_initialize_impl (instanceKlassHandle this_k);
>> 1316   static void set_initialization_state_and_notify_impl
>> (instanceKlassHandle this_k, ClassState state, TRAPS);
>> 1317   static void call_class_initializer_impl (instanceKlassHandle
>> this_k, TRAPS);
>> 1318   static Klass* array_klass_impl (instanceKlassHandle this_k,
>> bool or_null, int n, TRAPS);
>> 1319   static void do_local_static_fields_impl (instanceKlassHandle
>> this_k, void f(fieldDescriptor* fd, Handle, TRAPS), Handle, TRAPS);
>> 1320   /* jni_id_for_impl for jfieldID only */
>> 1321   static JNIid* jni_id_for_impl (instanceKlassHandle this_k, int
>> offset);
>> 1322
>>
>> All the above should probably be nonstatic member functions on
>> InstanceKlass instead but had to be made static since a permgen gc
>> could have moved "this" out from under the execution.
>
> I wanted to leave this as a future cleanup, because I think the changes
> here would less cosmetic and probably would lead to more opportunity to
> clean things up.

Ok, fine by me.

>
> Thanks - can I make you reviewer?

I only looked at instanceKlass.hpp/cpp to see if you had done the change 
I asked about so I think not :)

Thanks for doing this cleanup!

/Mikael

>
> Coleen
>
>>
>> /Mikael
>>
>>>
>>> On 3/13/17 2:23 AM, David Holmes wrote:
>>>> Hi Coleen,
>>>>
>>>> Wow that was a hard slog! :)
>>>>
>>>> On 13/03/2017 2:18 PM, coleen.phillimore at oracle.com wrote:
>>>>>
>>>>> As requested by David on the closed part of this review, I fixed
>>>>> variable names of the form h_ik and klass_h where the 'h' indicated
>>>>> that
>>>>> the klass was in a handle.
>>>>
>>>> Thanks for that. But I'm afraid there are quite a number of other
>>>> patterns including the "h" still present:
>>>>
>>>> src/share/vm/aot/aotCodeHeap.cpp/.hpp: InstanceKlass* kh
>>>> src/share/vm/c1/c1_Runtime1.cpp: InstanceKlass* h
>>>> src/share/vm/ci/ciArrayKlass.cpp: Klass* h_k
>>>> src/share/vm/ci/ciInstanceKlass.cpp/.hpp: Klass* h_k
>>>> src/share/vm/ci/ciKlass.cpp/.hpp: Klass* h_k
>>>> src/share/vm/ci/ciMethod.cpp: Klass* h_recv, Klass* h_resolved (though
>>>> that code uses h_ when there doesn't appear to be a handle in use)
>>>> src/share/vm/ci/ciObjArrayKlass.cpp/.hpp: Klass* h_k
>>>> src/share/vm/ci/ciTypeArrayKlass.cpp/.hpp: Klass* h_k
>>>> src/share/vm/interpreter/interpreterRuntime.cpp: Klass* h_klass,
>>>> InstanceKlass* h_cp_entry_f1
>>>> src/share/vm/prims/jni.cpp:  Klass* h_k
>>>> src/share/vm/prims/jvm.cpp: InstanceKlass* kh, InstanceKlass* ik_h
>>>> src/share/vm/prims/jvmtiClassFileReconstituter.cpp: InstanceKlass* iikh
>>>> src/share/vm/prims/jvmtiClassFileReconstituter.hpp: InstanceKlass*
>>>> _ikh, InstanceKlass*  ikh()
>>>> src/share/vm/prims/jvmtiEnv.cpp: InstanceKlass* ikh, InstanceKlass*
>>>> instanceK_h
>>>> src/share/vm/prims/jvmtiEnvBase.cpp: Klass* ob_kh
>>>> src/share/vm/prims/jvmtiExport.cpp: Klass* _h_class_being_redefined
>>>> src/share/vm/prims/jvmtiImpl.cpp: InstanceKlass* ikh, Klass* ob_kh
>>>> src/share/vm/prims/jvmtiRedefineClasses.cpp: InstanceKlass* ikh
>>>> src/share/vm/prims/jvmtiTagMap.cpp: InstanceKlass* ikh
>>>> src/share/vm/prims/jvmtiThreadState.hpp: Klass* h_class
>>>> src/share/vm/prims/nativeLookup.cpp: Klass* kh
>>>> src/share/vm/prims/whitebox.cpp: InstanceKlass* ikh
>>>> src/share/vm/runtime/sharedRuntime.cpp: Klass* h_klass
>>>> src/share/vm/services/gcNotifier.cpp: InstanceKlass* mu_kh
>>>> src/share/vm/services/heapDumper.cpp: InstanceKlass* ikh
>>>>
>>>
>>> These were the ones I fixed and retested.
>>>>
>>>>> open webrev at http://cr.openjdk.java.net/~coleenp/8155672.01/webrev
>>>>
>>>> There are numerous code indentation issues with some of the changed
>>>> code (mainly around parameter/argument lists) - but they all seem to
>>>> be pre-existing so I decided not to try and call them out. You did fix
>>>> quite a few, and I don't think you introduced any new ones. :)
>>>>
>>>> The main thing to look for with use of handles internal to methods is
>>>> whether once changed to a direct Klass/InstanceKlass*, the variable
>>>> becomes redundant. You picked up on a few of these but I spotted a
>>>> couple of others (reading the patch file the context isn't always
>>>> sufficient to spot these):
>>>>
>>>> share/vm/c1/c1_Runtime1.cpp
>>>>
>>>>          { Klass* klass = resolve_field_return_klass(caller_method,
>>>> bci, CHECK);
>>>> -          init_klass = KlassHandle(THREAD, klass);
>>>> +          init_klass = klass;
>>>>
>>>> You don't need the klass local but can assign direct to init_klass.
>>>>
>>>>      // convert to handle
>>>> -    load_klass = KlassHandle(THREAD, k);
>>>> +    load_klass = k;
>>>>
>>>> Comment should be deleted, plus it seems you should be able to assign
>>>> to load_klass directly earlier through the switch instead of
>>>> introducing 'k'.
>>>
>>> This logic is not obvious and I'd rather not change it. init_klass and
>>> load_klass are used further down for different purposes.  I removed the
>>> comment though.
>>>>
>>>> ---
>>>>
>>>> src/share/vm/jvmci/jvmciEnv.cpp
>>>>
>>>> 117     Klass*  kls;
>>>>
>>>> This local is not needed as you can assign directly to found_klass now.
>>>
>>> Yes, that's better.
>>>>
>>>> ---
>>>>
>>>> Finally a meta-question re the changes in:
>>>>
>>>> src/share/vm/classfile/dictionary.hpp
>>>>
>>>> and the flow out from that. I'm unclear about all the changes from
>>>> Klass to InstanceKlass. Are all dictionary/hashtable entries
>>>> guaranteed to be instance classes?
>>>
>>> Yes, they are.   This avoided multiple InstanceKlass::cast() calls.
>>>>
>>>> ---
>>>>
>>>>
>>>>> Also, fixing InstanceKlass to not pass this_k can be done in a
>>>>> separate
>>>>> cleanup.
>>>>
>>>> Ok.
>>>
>>> Thank you for slogging through all of this.
>>>
>>> Coleen
>>>>
>>>> Thanks,
>>>> David
>>>>
>>>>> Thanks,
>>>>> Coleen
>>>>>
>>>>> On 3/12/17 11:32 AM, coleen.phillimore at oracle.com wrote:
>>>>>> Summary: Use unhandled pointers for Klass and InstanceKlass, remove
>>>>>> handles with no implementation.
>>>>>>
>>>>>> These are fairly extensive changes.  The KlassHandle types have been
>>>>>> dummy types since permgen elimination and were thought to be useful
>>>>>> for future features.  They aren't, so can be removed (see bug for
>>>>>> more
>>>>>> details).   This allows stricter typing because you can use the more
>>>>>> specific type, and using const more.  I didn't add const to these
>>>>>> changes, because of the cascading effect.
>>>>>>
>>>>>> The change isn't hard to review, just tedious.  The main bug that I
>>>>>> had was redeclaring a type inside a scope, and InstanceKlass::cast(k)
>>>>>> can't take a NULL k, whereas instanceKlassHandle ik(THREAD, k) could.
>>>>>>
>>>>>> It's so nice being able to single step on gdb without going into
>>>>>> KlassHandle constructors!
>>>>>>
>>>>>> open webrev at http://cr.openjdk.java.net/~coleenp/8155672.01/webrev
>>>>>> bug link https://bugs.openjdk.java.net/browse/JDK-8155672
>>>>>>
>>>>>> Tested with all hotspot jtreg tests, java/lang/invoke tests,
>>>>>> java/lang/instrument tests, all closed tonga colocated tests, and
>>>>>> JPRT.
>>>>>>
>>>>>> I can continue to hold this change for a convenient time for merging
>>>>>> purposes with other people's JDK10 changes that they've been holding,
>>>>>> or if there are other jdk9 changes that are likely to cause a problem
>>>>>> for merging.  I'll update the copyrights to 2017 on commit.
>>>>>>
>>>>>> Thanks,
>>>>>> Coleen
>>>>>
>>>
>

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