Request for review: 7132690 InstanceKlass:_reference_type should be u1 type

[Karen Kinnear]

Jiangli,

Looks good. 

thanks,
Karen

On Jan 25, 2012, at 1:32 PM, Jiangli Zhou wrote:

> Hi Vitaly and David,
> 
> I've updated the webrev to do a == check via the cast.
> 
> http://cr.openjdk.java.net/~jiangli/7132690/webrev.02/
> 
> Thanks,
> 
> Jiangli
> 
> On 01/24/2012 11:44 PM, David Holmes wrote:
>> On 25/01/2012 2:41 PM, Vitaly Davidovich wrote:
>>> Hi Jiangli,
>>> 
>>> I think doing the comparison via the cast and == check to make sure it
>>> "roundtrips" is better than explicit range check because this way you
>>> don't have to change the assert if you change the width of the type
>>> (e.g. using u2 instead of u1 would require updating the range).  Plus as
>>> Dean mentioned, it looks like the cast version is already used in the
>>> codebase.
>> 
>> Plus the range check assumes that the enum will never have negative values (not likely here but why preclude it).
>> 
>> David
>> 
>>> Cheers
>>> 
>>> Sent from my phone
>>> 
>>> On Jan 24, 2012 10:19 PM, "Jiangli Zhou" <jiangli.zhou at oracle.com
>>> <mailto:jiangli.zhou at oracle.com>> wrote:
>>> 
>>>    __
>>>    Hi Vitaly,
>>> 
>>>    Thanks for catching it! A range check seems to be more explicit in
>>>    this case:
>>> 
>>>    http://cr.openjdk.java.net/~jiangli/7132690/webrev.02/
>>> 
>>>    Thanks,
>>> 
>>>    Jiangli
>>> 
>>>    On 01/24/2012 04:17 PM, Vitaly Davidovich wrote:
>>>> 
>>>>    I think you'll be fully covered (including negative values) by
>>>>    doing the following instead of hard coding max value in the assert:
>>>> 
>>>>    assert(t == (u1)t, "doesn't fit")
>>>> 
>>>>    Sent from my phone
>>>> 
>>>>    On Jan 24, 2012 6:33 PM, "Jiangli Zhou" <jiangli.zhou at oracle.com
>>>> <mailto:jiangli.zhou at oracle.com>> wrote:
>>>> 
>>>>        The updated webrev is :
>>>>        http://cr.openjdk.java.net/~jiangli/7132690/webrev.01/
>>>> <http://cr.openjdk.java.net/%7Ejiangli/7132690/webrev.01/>
>>>> 
>>>>        Thanks,
>>>>        Jiangli
>>>> 
>>>>        On 01/24/2012 02:54 PM, Jiangli Zhou wrote:
>>>>>        Hi Vitaly,
>>>>> 
>>>>>        An assert in the setter probably is a good idea. I should
>>>>>        have added it when making the change. Thanks for the comments!
>>>>> 
>>>>>        Thanks,
>>>>>        Jiangli
>>>>> 
>>>>>        On 01/24/2012 02:13 PM, Vitaly Davidovich wrote:
>>>>>> 
>>>>>>        Hi Jiangli,
>>>>>> 
>>>>>>        This is probably overly paranoid so feel free to ignore, but
>>>>>>        should the setter in InstanceKlass assert that the passed in
>>>>>>        ReferenceType fits into a u1 instead of silently narrowing
>>>>>>        it? Or change the setter to take a u1 and make caller do the
>>>>>>        cast? This would prevent someone defining another member of
>>>>>>        the enum with an explicit value that doesn't fit into u1.
>>>>>>        Like I said, paranoia ... :)
>>>>>> 
>>>>>>        Thanks
>>>>>> 
>>>>>>        Sent from my phone
>>>>>> 
>>>>>>        On Jan 24, 2012 3:06 PM, "Jiangli Zhou"
>>>>>> <jiangli.zhou at oracle.com <mailto:jiangli.zhou at oracle.com>>
>>>>>>        wrote:
>>>>>> 
>>>>>>            Hi,
>>>>>> 
>>>>>>            Please review the change for 7132690:
>>>>>> 
>>>>>>            http://cr.openjdk.java.net/~jiangli/7132690/webrev.00/
>>>>>> <http://cr.openjdk.java.net/%7Ejiangli/7132690/webrev.00/>
>>>>>> 
>>>>>>            It changes InstanceKlass::_reference_type from
>>>>>>            ReferenceType to u1. The ReferenceType is defined as an
>>>>>>            enum with 6 values
>>>>>>            (src/share/vm/utilities/globalDefinitions.hpp). The
>>>>>>            change saves 4-byte for each class.
>>>>>> 
>>>>>>            Tested with runThese and ute vm.quick.testlist. Ran jprt.
>>>>>> 
>>>>>>            Thanks,
>>>>>> 
>>>>>>            Jiangli
>>>>>> 
>>>>> 
>>>> 
>>> 
>