Null statement (NOP or CONTINUE)

[mister_e]

Well, it really depend on how the above is processed by the compiler, and on which architecture as well

Usually clearing a Variable would imply a simple asm line
CLRF _DUMMY

Or
MOVLW 0
MOVWF _DUMMY

BUT this assume you're on the right BANK... if BANK sensitive at all. Even though, there's several way to switch between BANK... and this still bring the idea of how they do it in background.

To me, NOP or GOTO $+1 (or GOTO $+2 for 18) are the best way, as they use a fixed instruction cycle and BANK insensitive AND you don't need any DUMMY variable AND you don't need to know the background process. But it's me