VM_Extent.fromInt(bitmapSets[sizeClass]<<(LOG_BYTES_IN_ADDRESS+LOG_SET_SIZE)));
VM_Extent.fromInt(bitmapSets[sizeClass]<<LOG_BYTES_IN_ADDRESS));
  protected final void postExpandSizeClass(VM_Address block, int sizeClass){    Memory.zeroSmall(block.add(BITMAP_BASE), 		     VM_Extent.fromInt(bitmapSets[sizeClass]<<(LOG_BYTES_IN_ADDRESS+LOG_SET_SIZE)));  };