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Re: SSA usage question
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, Richard Henderson <rth at redhat dot com>
- Date: Mon, 07 Jun 2004 12:35:22 -0400
- Subject: Re: SSA usage question
- Organization: Red Hat Canada
- References: <10406071632.AA10730@vlsi1.ultra.nyu.edu>
On Mon, 2004-06-07 at 12:32, Richard Kenner wrote:
> OK, but what's really important is that the computation needed to get
> 'v' and 'x' must be explicitly expanded in the GIMPLE code.
>
> Sure, but that's what gimplify_expr will do, right?
>
Yes. In theory, all you do is request a gimple_val in the 2nd and 3rd
operand to the ARRAY_REF.
> Even if it's simple enough to be trivially dead.
>
> It can't be dead.
>
> But it can be constant. Is it worth filling in these fields even in
> the constant case?
>
Yes, we do need the information. If the constants come from something
like:
x = 3
v = 8
... a[i,x,v]
...
x = 3
v = 8
a[j,x,v] ...
The dead assignments will be cleaned up by the optimizers.
Diego.