prog.From = a[0]
			if a[1].Type == obj.TYPE_REG {
				prog.Reg = p.getRegister(prog, op, &a[1])
			} else {
				prog.AddRestSource(a[1])
			}
			prog.To = a[2]
		default:
			p.errorf("TODO: implement three-operand instructions for this architecture")
			return
		}
	case 4:
		if p.arch.Family == sys.ARM {
			if arch.IsARMBFX(op) {
				// a[0] and a[1] must be constants, a[2] and a[3] must be registers