Incorrect bitfield aliasing with Tree SSA

[Richard Kenner]

> > you have the fields A and C conflicting, which is wrong.
> 
> Well, that is where structure-field aliasing comes in.  The two cannot
> even alias for addressable fields:

At tree level I'll take your word for it, but what about RTL level?
Is that nonconflicting status passed to RTL?  What *is* the problem
with just using the parent alias set?

I continue to strongly feel that the field type shouldn't be used
for ANYTHING!