no requirement on the part of the developer to even know that it is
performing parallel dynamically-partitioned operations.
+nmigen 32-bit Signal:
+
+ a : .... .... .... .... (32 bits)
+
+Dynamically-partitioned 32-bit Signal subdivided into 4 by 3 partition bits:
+
+ partition: P P P (3 bits)
+ a : .... .... .... .... (32 bits)
+ exp-a : ....P....P....P.... (32+3 bits, P=1 if no partition)
+
Links:
* <https://bugs.libre-soc.org/show_bug.cgi?id=458> m.If/Switch