fix to swap all members in StringMapImpl::swap

[takuto.ikuta]

Nico, can I ask you to review this simple fix?

[davide]

Testcase?

[thakis]

I just found this and realized I missed it for a very long time. I tried adding a test case, but while doing so I think this change doesn't actually change behavior: StringMapImpl::swap is only used by StringMap<T>::operator=, which guarantees that lhs and rhs have the same T and the underlying StringMapImpls the same ItemSize for that reason.

Did this cause any issues in practice?

[takuto.ikuta]

Sorry, this is not important, let me abandon this.

llvm/include/llvm/ADT/StringMap.h

public:
   bool empty() const { return NumItems == 0; }
   unsigned size() const { return NumItems; }
 
   void swap(StringMapImpl &Other) {
     std::swap(TheTable, Other.TheTable);
     std::swap(NumBuckets, Other.NumBuckets);
     std::swap(NumItems, Other.NumItems);
     std::swap(NumTombstones, Other.NumTombstones);
+    std::swap(ItemSize, Other.ItemSize);
   }
 };
 
 /// StringMapEntry - This is used to represent one value that is inserted into
 /// a StringMap.  It contains the Value itself and the key: the string length
 /// and data.
 template<typename ValueTy>
 class StringMapEntry : public StringMapEntryBase {