alignment: store_one_arg vs emit_push_insn

[DJ Delorie]

> Clearly this is all confused.  There's no need to glean the value
> of the argument from a passed in "align" parameter.  If the value
> is in memory then MEM_ALIGN will contain the proper alignment.
> True, MEM_ALIGN did not exist when this routine was written, but
> that doesn't mean we can't clean this up now.

So, what would a minimal fix be?  Ignore align and read MEM_ALIGN from
the parameters?

> I think both move_by_pieces and emit_push_insn should be reorged
> and clarified that the alignment parameter applies only to the 
> stack (i.e. to==NULL in the move_by_pieces case).

move_by_pieces is fairly naive about mem-mem transfers.  It doesn't
look like it would be able to take advantage of knowing both
alignments without a large change.  Would it be sufficient if it just
chose the minimum of the available alignment?  If so, then most of the
"reorg" would just be commenting the new semantics.