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Re: [PATCH][RFC][4.4] Add may-alias oracle, make SCCVN use it
On Thu, 6 Dec 2007, Eric Botcazou wrote:
> > the two references i[0] and i[1] have !refs_must_alias_p relationship,
> > while alias_sets_must_conflict_p returns true here. One could use
> > alias_sets_must_conflict_p as "early out" if that returns false, but
> > otherwise I don't see how this helps here.
>
> Yes, that's what I was thinking of, like in refs_may_alias_p.
Actually thinking about it we can only do
bool
refs_must_conflict_p (tree ref1, tree ref2)
{
if (!alias_sets_conflict_p (get_alias_set (ref1), get_alias_set (ref2)))
return false;
return operand_equal_p (ref1, ref2);
}
that is, we have to use may-alias for the early out. But I doubt this
makes the function any cheaper - in fact I think it makes it more
expensive.
Richard.