I don't recall having thought about this when providing IEABRC. But the conclusion that it's not going to get added is likely a correct one.
Without a complex macro (which definitely is not going to happen), changing NOP to JNOP for the cases Jonathan Scott mentioned will reject operands that are fully valid (avoiding RC=4 if you suppress ASMA212W Branch address alignment for <x> unfavorable). I believe his case is a very common one of using the operand of NOP for diagnostic purposes. While NOP perhaps isn't a branch (because it never goes anywhere), it is the conditional branch opcode so could have been a candidate for conversion. But functionally it is not necessary. Anyone who truly wants conversion of the operand for some reason could avoid using NOP and code a conditional branch with mask 0. That will get converted. Peter Relson z/OS Core Technology Design
