One reason for the Assembler's not having implemented a fuller set of
extended branch mnemonics is that once the original ("incomplete") set
wasprovided, many users implemented their own macro-based extensions.Given the decades-long lack of a mechanism to choose between a set of built-in assembler mnemonics and a wide variety of user-implemented mnemonics (not all of which were the same) it seemed safest to stay with the original set. It could be very risky for the assembler to provide built-in extended mnemonics that had slightly different branch masks from those a customer was already using, because programs could behave very differently with no warning or other indication. Regards... John Ehrman
