[PATCH] Make alias_sets_conflict_p less conservative

[Richard Kenner]

> > > This effectively makes a set with an alias-set zero child equivalent
> > > to alias-set zero itself, which doesn't make sense.
> > 
> > It's not equivalent, but close.
> 
> It _is_ equivalent to alias set zero, as every member in either set
> is a member of the other set.

This is a distinction without a difference.  Just because something
conflicts with all other alias sets doesn't mean that it *is* alias
set zero, just that it *acts* like it.

> Now, lets assume we don't want a alias set zero member to leak all its
> children.  

But why do you assume that?  It's wrong.  It's no more correct than
saying that it shouldn't "leak" a child of some other particular alias set.

> The question remains, in which practical cases we _do_ want the
> behavior that an alias set zero member makes the set itself effectively
> alias set zero. 

In any case where a member is alias set zero for a reason.

> (I can't think of a C structure where we want this behavior)

I can't either, but the fix is to not make 'char' alias set zero!