// return the first source operand in p.RestArgs.
// In combination with Prog.From and Prog.To it makes common 3 operand
// case easier to use.
func (p *Prog) GetFrom3() *Addr {
	for i := range p.RestArgs {
		if p.RestArgs[i].Pos == Source {
			return &p.RestArgs[i].Addr
		}
	}
	return nil
}

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

		// Should not happen but might as well show it if it does.
		fmt.Fprintf(w, "%s%v", sep, Rconv(int(p.Reg)))
		sep = ", "
	}
	for i := range p.RestArgs {
		if p.RestArgs[i].Pos == Source {
			io.WriteString(w, sep)
			WriteDconv(w, p, &p.RestArgs[i].Addr)
			sep = ", "
		}
	}

	if p.As == ATEXT {
		// If there are attributes, print them. Otherwise, skip the comma.

	//                                "ADDEX R3, R4, $3, R5"
	case AVSHASIGMAW, AVSHASIGMAD, AADDEX, AXXSLDWI, AXXPERMDI:
		if len(p.RestArgs) == 2 && p.Reg == 0 && p.RestArgs[0].Addr.Type == obj.TYPE_CONST && p.RestArgs[1].Addr.Type == obj.TYPE_REG {
			p.Reg = p.RestArgs[1].Addr.Reg
			p.RestArgs = p.RestArgs[:1]
		}
	}

	if c.ctxt.Headtype == objabi.Haix {
		c.rewriteToUseTOC(p)
	} else if c.ctxt.Flag_dynlink {

					return
				}
				// For ARM64 CASP-like instructions, its 2nd destination operand is register pair(Rt, Rt+1) that can
				// not fit into prog.RegTo2, so save it to the prog.RestArgs.
				prog.AddRestDest(a[2])
			default:
				prog.From = a[0]
				prog.Reg = p.getRegister(prog, op, &a[1])
				prog.To = a[2]
			}
		case sys.I386:
			prog.From = a[0]
			prog.AddRestSource(a[1])