+************************************************************************
+* performance issues
+************************************************************************
+
+Several areas can be cleaned up to make mandoc even faster. These are
+
+- cache `Bd' display types as `Bl' types are cached (this primarily
+ improves code-size by removing the a2disp type functions)
+
+- improve caching mechanism to handle other per-element arguments so
+ that they need not be recalculated between front- and back-ends (also
+ reduces code size and complexity)
+
+- improve hashing mechanism for macros (quite important: performance)
+
+- improve hashing mechanism for characters (not as important)