// fmt.Printf("%s %+v\n", op, a)
	prog := &obj.Prog{
		Ctxt: p.ctxt,
		Pos:  p.pos(),
		As:   op,
	}
	switch len(a) {
	case 0:
		// Nothing to do.
	case 1:
		if p.arch.UnaryDst[op] || op == obj.ARET || op == obj.AGETCALLERPC {
			// prog.From is no address.
			prog.To = a[0]
		} else {
			prog.From = a[0]
			// prog.To is no address.
		}