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Re: GCC 4.2.0 Status Report (2007-03-22)
> The lang hook is supposed to mark the variable as addressable.
> The lang hook should not be changing other things that have an affect
> on the *middle end*. No exceptions.
But how is it "supposed to mark the variable as addressable"? If this
just means setting TREE_ADDRESSABLE, what's the point of having the hook?
And if it does something *else*, how is the middle-end supposed to
know how to undo it?
I guess what I'm arguing for here is either the removal of the lang
hook or the addition of one to set a decl *non-addressable*. As far
as I'm concerned, I think the removal is better, but both are OK with me.
> > Moreover, what if what you're taking the address of is a COMPONENT_REF
> > or some such. Are we saying that's not allowed anymore? Some lang-hooks
> > look through them to set TREE_ADDRESSABLE on the underlying decl, but
> > your patch only calls it on a DECL_P.
> What are you talking about?
> The aliaser will remove tree addressable from DECL's if they do not
> have their address taken. This includes removing addressable from "a"
> if we had &a.b.c.d, it was the only address taking of a, and later
> eliminated it.
I'm talking about *setting* TREE_ADDRESSABLE on "a" in your example.
Exactly who will do that with your patch?
> > I think we need to step back a bit and get a definition we can all agree
> > on here first.
>
> A definition of what, exactly?
Of the precise relationship between TREE_ADDRESSABLE and the lang hook
and the issue of how to "undo" what the hook might have done.