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From "Rana Dasgupta" <rdasg...@gmail.com>
Subject Re: [DRLVM] 64-bit support with compressed pointer
Date Fri, 02 Feb 2007 17:09:56 GMT
We can clean some of this up when doing the Windows64 port. Then wait for
the jit to support the functionality, and switch the default.

On 2/2/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
>
> Thanks, Aleksey. Well, it's not that easy. The object header layout
> change has interactions with some other modules like threading.  And
> my original question is not about how to hack the code base for
> non-compressed pointer. I was just thinking it might be a good idea to
> make compressed pointer only a toggle-able optimization.
>
> Thanks,
> xiaofeng
>
> On 2/2/07, Aleksey Ignatenko <aleksey.ignatenko@gmail.com> wrote:
> > I suppose there is no easy way to do that, but one can scan all places
> where
> >
> > #ifdef _EM64T_ appears and change appropriate places to something like
> > #ifdef _COMPRESSED_MODE. Plus scan such places like gc_types.h in gc_cc,
> > there is object header:
> >     VT32 vt_raw;
> >     unsigned info;
> > You need to have VT64 vt_raw;  for 64 bit mode.
> >
> > p.s. In some of discussions I read that compressed mode (comparing to
> > uncompressed one) improved performance on about 13% on em64t.
> >
> > On 2/2/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> >
> > > Yes, that's exactly my question. I couldn't find an easy way to turn
> > > off this compressed-ptr optimization. It's a little bit surprising me.
> > > :-)
> > >
> > > Thanks,
> > > xiaofeng
> > >
> > > On 2/2/07, Aleksey Ignatenko <aleksey.ignatenko@gmail.com> wrote:
> > > > Did you check that it works on 64 bit mode with uncomressed
> references.
> > > > I remember some time ago there were issues like hard coded
> compressed
> > > > references used in JIT (or probably somewhere else) in 64bit mode.
> > > >
> > > > Best regards,
> > > > Aleksey.
> > > >
> > > > On 2/2/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> > > > >
> > > > > Hi, current 64bit support uses compressed reference pointer by
> > > > > default, i.e., a 64bit reference is stored as a 32bit value plus
a
> > > > > (global) base address. This can reduce the footprint of working
> set
> > > > > and at the same time improve cache locality. But this has max heap
> > > > > size limitation.
> > > > >
> > > > > I wonder why not use non-compressed pointer as by default, and the
> > > > > compressed pointer is only an optimization that can be applied
> when
> > > > > desirable. Comments?
> > > > >
> > > > > Thanks,
> > > > > xiaofeng
> > > > >
> > > >
> > > >
> > >
> >
> >
>

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