Boxed types and constat propagation
forax at univ-mlv.fr
Mon Apr 23 16:55:40 PDT 2012
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
Sure, it's easy, in ciField.cpp, there is a method named
you can add
or change the flag TrustFinalNonStaticFields to true if you have build
the fastdebug VM.
> 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
>> It seems that because of the cache used in Integer.valueOf(), the JIT
>> that the Integers are not escapable.
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