prog.To = a[2]
		case sys.AMD64:
			prog.From = a[0]
			prog.AddRestSource(a[1])
			prog.To = a[2]
		case sys.ARM64:
			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
				}