// AddRestSource assigns []Args{{a, Source}} to p.RestArgs.
func (p *Prog) AddRestSource(a Addr) {
	p.RestArgs = append(p.RestArgs, AddrPos{a, Source})
}

// AddRestSourceReg calls p.AddRestSource with a register Addr containing reg.
func (p *Prog) AddRestSourceReg(reg int16) {
	p.AddRestSource(Addr{Type: TYPE_REG, Reg: reg})
}

// AddRestSourceConst calls p.AddRestSource with a const Addr containing off.