Re: [patch] for PR 18040

[Jason Merrill <jason@redhat.com>]

On Tue, 19 Oct 04 18:51:10 EDT, kenner@vlsi1.ultra.nyu.edu (Richard Kenner) wrote:

>     In fact, some people have argued that
>     we should be breaking up _all_ chains of dereference operations so
>     that the optimizers can see better.
>
> The problem, however, is that the SSA-based optimizations operate mostly
> on *scalars*, so making more aggregate temporaries, which is what
> happens when you break up those chains, creates things that are hard to
> remove under the present optimization environment.
>
> Moreover, some of those temporaries will be of variable-size, which
> we don't currently support.

I don't think anybody is suggesting that we break up reference chains in a
way that would introduce aggregate temporaries.  Only things that can be
expressed like

           t = &a.b;
a.b.c  =>    t->c

"t" here is a scalar temporary, so the optimizers should be able to do
useful things with it.

Jason