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Re: RFC: GIMPLE tuples. Design and implementation proposal
- From: Andi Kleen <andi at firstfloor dot org>
- To: Richard Henderson <rth at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: 11 Apr 2007 13:53:15 +0200
- Subject: Re: RFC: GIMPLE tuples. Design and implementation proposal
- References: <461B175A.1050407@redhat.com.suse.lists.egcs> <m3mz1gnllz.fsf@localhost.localdomain.suse.lists.egcs> <20070411010342.GB25174@redhat.com.suse.lists.egcs>
Richard Henderson <rth@redhat.com> writes:
> On Tue, Apr 10, 2007 at 11:13:44AM -0700, Ian Lance Taylor wrote:
> > The obvious way to make the proposed tuples position independent would
> > be to use array offsets rather than pointers.
>
> I suggest instead, if we want something like this, that we make
> the references be pc-relative. So something like
If you go this way (and require special GC/debugger support) you
could as well xor next/prev too and save another field.
Adding a xor is basically free and much cheaper than any cache miss
from larger data structures.
The only thing that wouldn't work is that when you have a pointer
to an arbitary element (without starting from beginning/end first)
you couldn't get previous or next.
-Andi