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

[Jiangli Zhou]

Hi Karen,

Thanks for the review.

Jiangli

On 01/25/2012 10:48 AM, Karen Kinnear wrote:
> 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
>>>>>>>