delegate().clear();
      }
    };
  }

  @Override
  public @Nullable Entry<K, V> firstEntry() {
    return delegate.firstEntry();
  }

  @Override
  public K firstKey() {
    return delegate.firstKey();
  }

  @Override
  public @Nullable Entry<K, V> floorEntry(K key) {
    return delegate.floorEntry(checkValid(key));
  }

  @Override
  public @Nullable K floorKey(K key) {

	// ARM64 register list follows ARM64 instruction decode schema
	// | 31 | 30 | ... | 15 - 12 | 11 - 10 | ... |
	// +----+----+-----+---------+---------+-----+
	// |    | Q  | ... | opcode  |   size  | ... |

	firstReg := int(list & 31)
	opcode := (list >> 12) & 15
	var regCnt int
	var t string
	switch opcode {
	case 0x7:
		regCnt = 1
	case 0xa:
		regCnt = 2
	case 0x6:
		regCnt = 3
	case 0x2:

        delegate().clear();
      }
    };
  }

  @Override
  public @Nullable Entry<K, V> firstEntry() {
    return delegate.firstEntry();
  }

  @Override
  public K firstKey() {
    return delegate.firstKey();
  }

  @Override
  public @Nullable Entry<K, V> floorEntry(K key) {
    return delegate.floorEntry(checkValid(key));
  }

  @Override
  public @Nullable K floorKey(K key) {

    @Nullable
    @Internal
    public T getFirstEnabled() {
        SortedMap<String, T> map = enabled.getAsMap();
        if (map.isEmpty()) {
            return null;
        } else {
            return map.get(map.firstKey());
        }
    }

    protected <N extends T> N add(Class<N> clazz, Object... constructionArgs) {
        N report = getInstantiator().newInstance(clazz, constructionArgs);
        String name = report.getName();

      return new TreeRow(rowKey, fromKey, upperBound);
    }

    @Override
    public C firstKey() {
      updateBackingRowMapField();
      if (backingRowMap == null) {
        throw new NoSuchElementException();
      }
      return ((SortedMap<C, V>) backingRowMap).firstKey();
    }

    @Override
    public C lastKey() {
      updateBackingRowMapField();

      return new TreeRow(rowKey, fromKey, upperBound);
    }

    @Override
    public C firstKey() {
      updateBackingRowMapField();
      if (backingRowMap == null) {
        throw new NoSuchElementException();
      }
      return ((SortedMap<C, V>) backingRowMap).firstKey();
    }

    @Override
    public C lastKey() {
      updateBackingRowMapField();

			}
		} else if rc.hasRegs() {
			firstReg := uint32(0)
			for i := 0; i < int(which); i++ {
				firstReg += uint32(len(aux.abiInfo.OutParam(i).Registers))
			}
			reg := int64(rc.nextSlice + Abi1RO(firstReg))
			a = makeOf(a, OpSelectN, []*Value{call})
			a.AuxInt = reg
		} else {

			ext := tok.String()
			curArrangement, err := arch.ARM64RegisterArrangement(reg, name, ext)
			if err != nil {
				p.errorf(err.Error())
			}
			if firstReg == -1 {
				// only record the first register and arrangement
				firstReg = int(reg)
				nextReg = firstReg
				arrangement = curArrangement
			} else if curArrangement != arrangement {
				p.errorf("inconsistent arrangement in ARM64 register list")

	// more than one of each per m, p, and goroutine.
	firstGen := traceNextGen(trace.lastNonZeroGen)

	// Reset GC sequencer.
	trace.seqGC = 1

	// Reset trace reader state.
	trace.headerWritten = false
	trace.readerGen.Store(firstGen)
	trace.flushedGen.Store(0)

	// Register some basic strings in the string tables.
	traceRegisterLabelsAndReasons(firstGen)

	// Stop the world.
	//

    return ImmutableSortedSet.copyOf(comparator, sortedDelegate.keySet());
  }

  public Comparator<? super K> comparator() {
    return comparator;
  }

  @CheckForNull
  public K firstKey() {
    return sortedDelegate.firstKey();
  }

  @CheckForNull
  public K lastKey() {
    return sortedDelegate.lastKey();
  }

  @CheckForNull
  K higher(K k) {