Ports often need to define similar patterns for two or more different modes. For example:
SFmodepatterns tend to be very similar to the
SImodepointers in one configuration and
DImodepointers in another, it will usually have very similar
DImodepatterns for manipulating pointers.
Mode macros allow several patterns to be instantiated from one
.md file template. They can be used with any type of
rtx-based construct, such as a