6953576: bottom_type for matched AddPNodes doesn't always agree with ideal
Summary:
Reviewed-by:

6715633 added an assert to make sure that the adr_type of nodes
doesn't change during matching. If the address pieces are matched
separately this assert can fail because the logic in
AddPNode::mach_bottom_type isn't the equivalent to
AddPNode::bottom_type. The fix is to simply capture the bottom_type
when transforming the nodes by making AddP matches inherit from
MachTypeNode. This was originally discovered in the ia64 port but I
reproduced it by disabling the use of complex addressing modes to
force the matching AddPs separately.