DATA_ALIGNMENT vs. DECL_USER_ALIGNMENT

[Richard Kenner]

    Then it sounds like we need a way for the port to specify or the
    front-end to query the minimum alignment allowed for the target.  This
    would allow the front-end to statically know the alignment of the type
    while maintaining the target requirements.

The issue isn't *minimum*, but *exact*.  The front end needs to know what 
the alignment for a particular type will be.  Yes, it is possible for it
to make on-the-fly calls to the back end to lay out types incrementally, but
that's a very difficult thing to do due to dependencies of types on variables.
It's not clear it's worth it.