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Date: Thu, 16 Jul 2009 16:04:00 -0000
Message-ID: <cb9d34b20907160903m3d072f3eg6d17e3a09dab18a2@mail.gmail.com>
Subject: Re: How could I get alias set information from data_reference_p
From: Sebastian Pop <sebpop@gmail.com>
To: Daniel Berlin <dberlin@dberlin.org>
Cc: Li Feng <nemokingdom@gmail.com>, Richard Guenther <richard.guenther@gmail.com>,  	Tobias Grosser <grosser@fim.uni-passau.de>, gcc@gcc.gnu.org,  	gcc-graphite <gcc-graphite@googlegroups.com>
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On Thu, Jul 16, 2009 at 10:45, Daniel Berlin<dberlin@dberlin.org> wrote:
> So if i understand you right, it seems all you've done is inverted the
> existing alias/points-to sets.
> IE instead of saying A has B, C, D in it's alias set, you are saying B
> is in the alias set of A, C is in the alias set of A, D is in the
> alias set of A.
>
> Effectively,
>
> A -> {B, C, D}
> B -> {C, D, E}
> becomes
> B -> A
> C -> A, B
> D -> A ,B
> E -> B
>

Yes, this is correct.

> Then you are assigning numbers to the sets that appear on the RHS.

Correct.

> You still end up with bitmaps, and you still have to intersect them
> (or describe containment some other way and do containment queries).
>
> For a large program, this mapping is actually massive and quite
> expensive to compute

In the case of Graphite, the queries are limited to the data
references within a SCoP.  Usually a SCoP does not necessarily contain
huge amount of data references.  In the future, we may also set
restrictions on the number of data references that we allow in a SCoP.

Sebastian