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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [Fwd: Re: [DRLVM][JET] write barrier for Java (mmtk)]
Date Fri, 13 Oct 2006 14:31:27 GMT
Salikh,
Good catch!  You just saved the MMTk port 20 hours of debugging.  Thank you
:)



On 10/13/06, Salikh Zakirov <Salikh.Zakirov@intel.com> wrote:
>
>
> Weldon Washburn wrote:
> >> I actually stumbled on this bug during bringup.  I replaced
> >> ...plus(arrayOffset)... with ...plus(12)...  Its a hack.  But now it
> >> looks
> >> like I simply set ARRAY_BASE_OFFSET to 12 during <clinit>.  Does this
> >> seem
> >> right??
>
> By the way, the array base offset may differ depending on the platform and
> array type.
> As as I know, currently on 32 bit platform (ia32) the array base offset
> is 12 for types of size <= 4.
> Double[] and long[] arrays have array base offset 16.
>
> on 64 bit platforms, if the vtable pointers are compressed (they are now),
> the array base offset is the same as on 32 bit platforms.
>
> Should someone disable vtable reference compression, the array base offset
> will be always 16 (8 bytes vptr + 4 bytes flags + 4 bytes array size).
>
>
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-- 
Weldon Washburn
Intel Middleware Products Division

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