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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [DRLVM] what's the purpose to set NEXT_TO_HIGH_BIT_SET_MASK in object size?
Date Wed, 21 Mar 2007 11:59:46 GMT
If no one objects, I will try to remove this flag in DRLVM.


On 3/21/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> Hi, the source code for class preparation calls
> set_instance_data_size_constraint_bit() for three situations: special
> alignment requirement, having finalizer, and to be pinned. And the
> comments there say the constraint bit is for GC to understand.
> But current GC actually doesn't care about this bit, and simply masks
> it off. Does anybody know what are the situations for the size
> constraint bit to be set for allocation?
> I recall this kind of constraint bit was ORP legacy, when the
> intention was for gc_alloc_fast to be really fast, avoiding any
> special allocation treatment. So once the big flag is set,
> gc_alloc_fast will simply return NULL, and the VM will invoke gc_alloc
> to accomplish the allocation.
> Now DRLVM has different processing, and the GC doesn't use the flag in
> size for allocation. I wonder what is the real purpose of this size
> flag in allocation.
> Thanks,
> xiaofeng

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