Boxed types and constat propagation

[Rémi Forax]

On 04/24/2012 01:43 AM, Kohsuke Kawaguchi wrote:
>
> Any chance you can share that patch with us? It'd give me some 
> pointers into poking around JDK code, now that I learned how to build 
> it...

Sure, it's easy, in ciField.cpp, there is a method named 
trust_final_non_static_fields(),
you can add

if (holder->is_in_package("java/lang"))
     return true;

or change the flag TrustFinalNonStaticFields to true if you have build 
the fastdebug VM.

cheers,
Rémi

>
> On 04/23/2012 04:29 PM, Rémi Forax wrote:
>> On 04/24/2012 12:57 AM, Kohsuke Kawaguchi wrote:
>>>  On 04/23/2012 11:18 AM, Rémi Forax wrote:
>>>>>   So again, I don't see how shifting from method handle tree to byte
>>>>>   code generation would somehow make this non-issue.
>>>>
>>>>  In fact, it's easy to know that a.foo() is a boolean because
>>>> &&   can be only applied on booleans so the invokedynamic call
>>>>  corresponding to a.foo() should return a boolean.
>>>>     From the compiler perspective, you have to back-propagate
>>>>  the excepted type from the root to the leaf.
>>>
>>>  Charles was alluding to the same thing, so I was thinking about this,
>>>  and I think I understand it now.
>>>
>>>  That's a lot of optimization that I otherwise wouldn't have to do, if
>>>  only boxed types and constant propagation worked well, but yeah, I see
>>>  how it can work now.
>>>
>>>  Thanks for all the insights.
>>
>> BTW, I've patched the JIT to consider all final fields of a class of
>> java/lang as truly final
>> but that not enough for having the escape analysis to work with 
>> integers.
>> It seems that because of the cache used in Integer.valueOf(), the JIT
>> considers
>> that the Integers are not escapable.
>>
>> Rémi
>>
>>
>
>