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Date: Fri, 18 Jan 2008 10:46:24 +0300
From: "Aleksey Shipilev" <aleksey.shipilev@gmail.com>
To: dev@harmony.apache.org
Subject: Re: [jira] Commented: (HARMONY-5399) [drlvm][jit] Enabling arraycopy
 optimization for primitive types when write barriers are enabled
In-Reply-To: <9623c9a50801172247k74525597m916714a026b6b61d@mail.gmail.com>
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References: <20845865.1200573276722.JavaMail.jira@brutus>
	 <880513.1200637837625.JavaMail.jira@brutus>
	 <9623c9a50801172247k74525597m916714a026b6b61d@mail.gmail.com>

Hi, Xiao Feng, Gregory,

I believe that current implementation of WB support for arraycopy is
good in case of unknown GC design. It would hit WB for every element
in the array, and then maintain compatibility across different GC
implementations, right?

I'm also thinking of specialized write barrier helper for arrays,
which would exploit your design but keep VM/JIT unaware of the
details.

Gregory, I have modified the patch to cover your concern, does it fits well?

Thanks,
Aleksey.

On Jan 18, 2008 9:47 AM, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> On Jan 18, 2008 2:30 PM, George Timoshenko (JIRA) <jira@apache.org> wrote:
> >
> >     [ https://issues.apache.org/jira/browse/HARMONY-5399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12560243#action_12560243 ]
> >
> > George Timoshenko commented on HARMONY-5399:
> > --------------------------------------------
> >
> > I have one consern.
> >
> > By the modification of "arraycopyOptimizable" you turn of the both
> >
> > genArrayCopy and
> > genArrayCopyRepMove
> >
> > optimizations of the arrays of Object types.
> >
> > BUT the first one, genArrayCopy, does not use REP instruction. It generates a copying loop so it can work with WB.
>
>
> For array write, it's ok to have only one WB for the whole object. In
> my current generational GC design, I use WB actually for object
> remembering rather than slot remembering. So one WB for the whole
> arraycopy is enough.
>
> (Well, write barrier support in DRLVM needs cleanup thenafter.)
>
> Thanks,
> xiaofeng
>
>
> >
> > > [drlvm][jit] Enabling arraycopy optimization for primitive types when write barriers are enabled
> > > ------------------------------------------------------------------------------------------------
> > >
> > >                 Key: HARMONY-5399
> > >                 URL: https://issues.apache.org/jira/browse/HARMONY-5399
> > >             Project: Harmony
> > >          Issue Type: Improvement
> > >         Environment: All
> > >            Reporter: Aleksey Shipilev
> > >         Attachments: WB-2.patch, WB-3.patch, WB-4.patch
> > >
> > >
> > > JIT arraycopy optimization is disabled automatically when WB are enabled. Attached patch re-enables arraycopy optimization for arrays of primitive types, which shouldn't interfere with WB activity.
> >
> > --
> > This message is automatically generated by JIRA.
> > -
> > You can reply to this email to add a comment to the issue online.
> >
> >
>
>
>
> --
> http://xiao-feng.blogspot.com
>