p.errorf("cannot reference %s without a symbol", name)
		}
		p.setPseudoRegister(a, name, false, prefix)
		return
	}
	a.Reg = r1
	if r2 != 0 {
		// TODO: Consistency in the encoding would be nice here.
		if p.arch.InFamily(sys.ARM, sys.ARM64) {
			// Special form
			// ARM: destination register pair (R1, R2).
			// ARM64: register pair (R1, R2) for LDP/STP.
			if prefix != 0 || scale != 0 {