switch {
			case arch.IsARM64STLXR(op):
				// ARM64 instructions with one input and two outputs.
				prog.From = a[0]
				prog.To = a[1]
				if a[2].Type != obj.TYPE_REG {
					p.errorf("invalid addressing modes for third operand to %s instruction, must be register", op)
					return
				}
				prog.RegTo2 = a[2].Reg
			case arch.IsARM64TBL(op):
				// one of its inputs does not fit into prog.Reg.
				prog.From = a[0]