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

[Rahul Raghavan]

Thank you Dean.

> -----Original Message-----
> From: Dean Long > Sent: Wednesday, February 17, 2016 1:44 PM > To: Rahul Raghavan; Roland Westrelin; hotspot-compiler-dev at openjdk.java.net
> 
> 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.
> >>>>
> >>>>
>