More on: Small static method marked not entrant, inlining reversed?

[Rémi Forax]

Le 22/09/2010 22:24, Tom Rodriguez a écrit :
>>>        
>>>> I wonder if the fix can improve performance of benchmarks that use java.util collection,
>>>> because this API uses a similar class hierarchy scheme.
>>>>
>>>>          
>>> There are normally more than 1 or 2 implementors of the collection interfaces so static information isn't as useful.  Much of the time the existing type profiling works great because we're only seeing a single type but of course there are cases where it falls down.
>>>        
>> Yes but most of collections inherits from an abstract class, AbstractList, AbstractCollection etc,
>> so even if there are more than 2 implementors, they can inherits from the same abstract class.
>>      
> Collections.java by itself contains 3 unique implementors of the each of the core collection interface to support checked, unmodifiable and synchronized variants.  These are unrelated to the abstract classes you mention above.  java.util.concurrent includes yet more unrelated variants.  So looking at the hierarchy is of little use for most of those interface types.  Anyway we can obviously do better than we are currently doing.
>
> tom
>
>    

You're right about checked, unmodifiable and synchronized, but checked 
and synchronized variants
are rarely used and unmodifiable should inherit from their abstract 
counterparts.
Also note that single and empty variants inherit from abstract versions.

For java.util.concurrent classes, queues (exactly blocking queues) are 
used in a polymorphic way,
the other classes like ConcurrentHashMap, CopyOnWriteArraySet, etc are 
rarely involved in
a polymorphic callsite.

Rémi