protected static final int getSizeClass(VM_Address block)
protected static final int getSizeClass(EXTENT bytes)
  protected static final int getSizeClass(VM_Address block)     throws VM_PragmaInline {    int value = VM_Magic.getMemoryInt(block.add(FREE_LIST_OFFSET));    value = (value & SIZE_CLASS_MASK)>>SIZE_CLASS_SHIFT;    return value;  }