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Re: Note on 109327

From: Dmitry Antipov
Subject: Re: Note on 109327
Date: Tue, 31 Jul 2012 17:50:43 +0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120713 Thunderbird/14.0

On 07/31/2012 05:33 PM, Tom Tromey wrote:

Dmitry> Yes. I'm always thinking about improving internal stuff, GC at first.
Dmitry> For me, the main motivation for BVAR, KVAR, FVAR etc. is the ability
Dmitry> to catch the moment when the pointer (e.g. Lisp_Object) within buffer,
Dmitry> or keyboard, of frame, etc. is read or written, which may be useful
Dmitry> to implement write barriers (see, for exmaple,
Dmitry> http://www.hoelzle.org/publications/write-barrier.pdf, but do not
Dmitry> get confused with http://en.wikipedia.org/wiki/Memory_barrier).

I think to do this well you will need separate macros for getting and

Sure, but it's almost impossible to do this at once. At the very beginning,
it's possible to "overestimate" barrier assuming that each XVAR (obj, field)
changes FIELD in OBJ; in the future, reads and writes may be separated, thus
giving a precise write barrier.


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