The Zimop extension defines 8 MOP instructions named MOP.RR.n, where n is an integer between 0 and 7, inclusive. Unless redefined by another extension, these instructions simply write 0 to X[xd]. Their encoding allows future extensions to define them to read X[xs1] and X[xs2], as well as write X[xd].
mop.rr.n xd, xs1, xs2Type: R