From: Andy Wingo <wingo@pobox.com>
To: ludo@gnu.org (Ludovic Courtès)
Cc: guile-user@gnu.org
Subject: Re: on coding a portable R6RS package supporting Guile and its FFI
Date: Wed, 06 Feb 2013 11:57:56 +0100 [thread overview]
Message-ID: <87k3qlemkr.fsf@pobox.com> (raw)
In-Reply-To: <87d2wee6kf.fsf@gnu.org> ("Ludovic Courtès"'s message of "Tue, 05 Feb 2013 23:31:28 +0100")
On Tue 05 Feb 2013 23:31, ludo@gnu.org (Ludovic Courtès) writes:
> This would be less of a problem if we had “immediate pointers” [0].
> Would the retagging in 2.1 allow this?
The tc3 itag allocation in wip-retagging is:
* tc3:
* 000: A heap object with a tag word on the heap
* 001: Some other immediate
* 010: A pair
* 011: Small integer (odd)
* 100: (Unallocated tc3.)
* 101: (Unallocated tc3.)
* 110: A struct
* 111: Small integer (even)
And SCM_IMP is:
#define SCM_IMP(x) (1 & SCM_UNPACK (x))
So perhaps 101 could be an immediate pointer. Dunno. Pretty nasty
stuff!
> (At FOSDEM, Luca Saiu rightfully noted that we could use 4-bit tags
> instead of 3-bit tags on 64-bit arches, which would give us the needed
> room here.)
GC_malloc still returns eight-byte aligned memory hunks on 64-bit, no?
Andy
--
http://wingolog.org/
next prev parent reply other threads:[~2013-02-06 10:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-17 10:53 on coding a portable R6RS package supporting Guile and its FFI Marco Maggi
2013-01-27 15:08 ` Ludovic Courtès
2013-01-28 3:00 ` Daniel Hartwig
2013-02-05 17:38 ` Andy Wingo
2013-02-05 19:29 ` Noah Lavine
2013-02-06 8:36 ` Andy Wingo
2013-02-06 13:25 ` Noah Lavine
2013-02-05 22:31 ` Ludovic Courtès
2013-02-06 10:57 ` Andy Wingo [this message]
2013-02-08 14:10 ` Ludovic Courtès
2013-02-08 14:37 ` Andy Wingo
2013-02-08 15:52 ` Ludovic Courtès
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