RFR(S): 6378256: Performance problem with System.identityHashCode in client compiler

[Dean Long]

Looks good.

dl

On 2/15/2016 12:52 AM, Rahul Raghavan wrote:
> Hi,
>
> Yes, Thank you for the points Roland.
> Changes and testing done.
>
> Latest webrev for review: http://cr.openjdk.java.net/~thartmann/6378256/webrev.05/
>
> Thanks,
> Rahul
>
>> -----Original Message-----
>> From: Roland Westrelin > Sent: Thursday, February 11, 2016 7:50 PM > To: Rahul Raghavan > Cc: hotspot-compiler-dev at openjdk.java.net
>>
>> Hi Rahul,
>>
>>> webrev: http://cr.openjdk.java.net/~thartmann/6378256/webrev.04/
>> Thanks for the updated webrev.
>>
>> It would be better if he declaration of inline_check_hashcode_from_object_header() is private. When it’s called:
>>
>> SharedRuntime::inline_check_hashcode_from_object_header()
>>
>> SharedRuntime:: is useless:
>>
>> inline_check_hashcode_from_object_header()
>>
>> is sufficient.
>>
>> Roland.
>>
>>> New changes done here are -
>>>   i. added new inline_check_hashcode_from_object_header() in SharedRuntime class [sharedRuntime.hpp] guarded with 'X86 &&
>> COMPILER1'
>>>   ii. required comment text justification done.
>>>
>>> Confirmed no issues with jprt testing (-testset hotspot) and unit tests.
>>>
>>> Thank you,
>>> Rahul
>>>
>>>> -----Original Message-----
>>>> From: Roland Westrelin > Sent: Monday, February 08, 2016 11:00 PM > To: Rahul Raghavan > Cc: hotspot-compiler-
>> dev at openjdk.java.net
>>>> Hi Rahul,
>>>>
>>>>> Please review revised patch, notes for JDK-6378256.
>>>>> https://bugs.openjdk.java.net/browse/JDK-6378256
>>>>>
>>>>>
>>>>> Latest webrev-03: http://cr.openjdk.java.net/~thartmann/6378256/webrev.03/
>>>> Thanks for making the change. I would say it’s better to add inline_check_hashcode_from_object_header() to sharedRuntime.hpp
>>>> with #ifdef X86 rather than have the inline declaration. Not sure what others think.
>>>>
>>>>>>> Can you justify the comments again?
>>>> I meant justify as text justification that is right align that comment:
>>>>
>>>>   36 // ---------------------------------------------------------------------------
>>>>   37 // Object.hashCode, System.identityHashCode can pull the hashCode from the header word
>>>>   38 // instead of doing a full VM transition once it's been computed.
>>>>   39 // Since hashCode is usually polymorphic at call sites we can't do
>>>>   40 // this optimization at the call site without a lot of work.
>>>>
>>>> and that comment
>>>>
>>>> 2019     // Object.hashCode, System.identityHashCode can pull the hashCode from the header word
>>>> 2020     // instead of doing a full VM transition once it's been computed.
>>>> 2021     // Since hashCode is usually polymorphic at call sites we can't do
>>>> 2022     // this optimization at the call site without a lot of work.
>>>>
>>>> Sorry for the confusion. The code looks good to me/
>>>>
>>>> Roland.
>>>>
>>>>