Re: [Jikesrvm-researchers] objects layout

[Hezi A. <he...@cs...>]

After a little thought I've understood that moving the status field is not
desirable (as the scalar access to that field will be different from the
array access).

The new idea is to store the object-address in the raw-address
(that will give me the opposite mapping: from raw_address to
the object_address without knowing the object size), is it possible to add
another header at the beginning of the scalar object?

 high mem		          low mem
 +------+---+-----...----+-----------+
 |status|TIB|  fields    |obj_address|
 +------+---+-----...----+----+------+
 	   ^ 	              |      ^
 	  obj                 |     raw
           ^------------------+

--Hezi.

On Sun, 20 Jan 2002, Hezi Azatchi wrote:

>
> I want to change the objects layout.
>
> Can I move the status word of the scalar and array objects so it will be
> located at the raw address (lowest address of object at heap)?
> Or it might interfere something?
>
> For the scalars it means to put the status at the beginning of the object
> instead of at the end. For arrays it means to swap the order of the TIB
> and the status.
>
> i.e.
> instead of:
>
> high mem		low mem
> +------+---+-----...----+
> |status|TIB|          |
> +------+---+-----...----+
> 	^ 	     ^
> 	obj         raw
>
> the object layout for scalar:
>
> +---+-----....----+------+
> |TIB|           |status|
> +---+-----....----+------+
>  ^                    ^
> obj                  raw
>
>
> I think it will solve my previous problem (I'll be able to get to the
> status region via the BlockControl with almost zero knowledge about the
> object).
>
> Any help would be appreciated,
>
> --Hezi.
>
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