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

[Roland Westrelin]

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.
>> 
>>