RFR(M) 8208999 Some use of Klass* should be replaced by InstanceKlass*
Ioi Lam
ioi.lam at oracle.com
Tue Aug 7 04:31:59 UTC 2018
Hi Coleen,
Thanks for the review. Updated webrev is here:
http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v02/
More comments below
On 8/6/18 3:36 PM, coleen.phillimore at oracle.com wrote:
>
> http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v01/src/hotspot/share/classfile/systemDictionaryShared.cpp.udiff.html
>
>
> 1007 return entry != NULL ? entry->instance_klass() :
> (InstanceKlass*)NULL;
>
> do you need this cast here?
>
Removed.
> http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v01/src/hotspot/share/memory/metadataFactory.hpp.udiff.html
>
>
> + static void free_array(ClassLoaderData* loader_data, const Array<T>*
> data) {
>
>
> But we are modifying the contents of the data (?). This is for
> deleting secondary_supers? I think maybe adding the const for them
> might be overkill.
>
> http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v01/src/hotspot/share/oops/klass.hpp.udiff.html
>
> - Array<Klass*>* _secondary_supers;
> + const Array<Klass*>* _secondary_supers;
>
> I think the improvement outweighs this messy part of this. This looks
> like a difficult thing to change.
>
I agree. I reverted the "const" for Klass::secondary_supers. I also
removed Array::as_const_array_of() since that will probably be abused by
people who don't read the comments. Instead, I added this in
InstanceKlass::compute_secondary_supers:
set_secondary_supers((Array<Klass*>*)(address)interfaces);
it's a little ugly but the effects are localized.
> http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v01/src/hotspot/share/oops/arrayKlass.cpp.udiff.html
>
>
> + set_super(Universe::is_bootstrapping() ? (InstanceKlass*)NULL :
> SystemDictionary::Object_klass());
>
>
> Do you need this cast? Object_klass() returns InstanceKlass - all of
> these do.
>
Removed.
Thanks
- Ioi
>
> This looks really good. Thank you for doing this!
>
> Coleen
>
>
>
> On 8/6/18 5:26 PM, Ioi Lam wrote:
>> Hi, please review this clean up
>>
>> https://bugs.openjdk.java.net/browse/JDK-8208999
>> http://cr.openjdk.java.net/~iklam/jdk12/8208999_klass_should_be_instanceklass.v01/
>>
>>
>> I changed the following APIs so that we can avoid many unnecessary
>> type casts
>> from Klass* -> InstanceKlass*.
>>
>> Klass::java_super() -> now returns InstanceKlass*
>> InstanceKlass::local_interfaces() -> Array<InstanceKlass*>*
>> InstanceKlass::transitive_interfaces() -> Array<InstanceKlass*>*
>>
>> I also modified APIs in SystemSictionary and SystemSictionary to
>> return InstanceKlass*
>> where possible.
>>
>> Most changes are mundane, but here are some notable changes:
>>
>> 1. To save space, Klass::_secondary_supers (an Array<Klass*>*) may be
>> pointing
>> to the same array as InstanceKlass::_transitive_interfaces (an
>> Array<InstanceKlass*>*).
>>
>> To make this happen, I added Array::as_const_array_of().
>> See InstanceKlass::compute_secondary_supers() and array.h.
>>
>> I've added enough 'const' and asserts to catch mis-uses of this type
>> of casting. If someone has a better suggestion, please let me know.
>>
>> 2. I changed Klass::_secondary_supers to 'const Array<Klass*>*' because
>> of #1.
>>
>> There are many pointers returned by Klass/InstanceKlass that
>> should be
>> 'const', as most callers should read them only without modifying,
>> but that's
>> outside the scope of this RFE.
>>
>> 3. SystemDictionary::resolve_super_or_fail() currently accepts the
>> format
>> of "Ljava/lang/Object;" for the "super_name" parameter. I am
>> keeping the
>> same behavior in my patch. However, I wonder if this actually correct
>> per JVMLS. I filed JDK-8209030.
>>
>> See the call to resolve_instance_class_or_null_helper from
>> resolve_super_or_fail.
>>
>>
>> Testing: hs tiers 1/2/3/4
>>
>> Thanks
>> - Ioi
>
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