[userbinator]

I remember there was a "never" condition, which was present just for completeness; it turns out ARM eventually found that having 2^28 different NOPs would not be a good use of opcode space, so it's now a special extension for newer instructions...

[kybernetikos]

I seem to recall from my ARM Assembler coding days that there was also a noop instruction, which of course could be conditional itself, so if you didn't actually want to do the NOOP, you could do NOOP-NE, which wouldn't do anything twice over.

[talideon]

From my days coding ARM assembly on the Acorn Archimedes, NOP was typically an alias for MOV R0,R0 (which effectively did nothing) rather than being its own instruction.

[danellis]

And if you ever needed to manually patch in an easy-to-remember NOP, 0x00000000 was ANDEQ R0, R0, R0.