There is no such thing as a DWIM.

DWIM = Do What I Mean

It's the classic "joke instruction" which illustrates why computers are so "unnatural" to mere humans : they can't do telepathy and they require clear, unambiguous and effective code sequences, using instructions that they already have, operating on data they can reasonably manage...

When creating an instruction set architecture, simplicity is the rule. Unless you design an application-specific processor (such as a DSP), stick to the very basics. Don't include an instruction that requires a logic diagram you can't easily draw on a napkin and find the lowest common denominator to prevent duplication.

If you're familiar with the RISC methodology, this sounds obvious, but most beginners (including me...) want to include "their instruction" because they don't know how to use the existing methods. Have a look at the Hackmem and similar "programming tricks" :-)