It might be a whimsical notion occurring too late in the game, but a complement-and-add with carry (CDC) or negate-and-add (NDD) instruction would obviate the need to swap arguments in some cases. I have plenty of opcode slots in my 65m32, so it will definitely have at least one of those before it's ready for prime-time. "Whimsical" and "late" are integral parts of my personal mantra.

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Got a kilobyte lying fallow in your 65xx's memory map? Sprinkle some VTL02C on it and see how it grows on you!

Mike B. (about me) (learning how to github)

When programming in assembly language, or perhaps using a non-recursive descent compiler without too much intelligence, it's fairly easy to set up the evaluation order of the operands for instructions like CMP and SUB/SBC where operand order is important. On the other hand, having done only a minimal amount of 8086 assembly language programming, I was surprised at how flexible some of the instructions are with respect to operand order.

So it's not a whimsical notion to contemplate about being able to support reverse operand order in your instruction set. The simple accumulator / memory architecture of the 6502/65C02 makes it difficult to easily swap operand order for instructions when it matters. A three register instruction set architecture makes it much easier to control operand order.

As always, Mike, I enjoy hearing from you. I would never have thought of naming the instructions in the manner you suggested. I just don't think that way.

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Michael A.