[ADT] Teach FoldingSet to be movable.

This is a very minimal move support - it leaves the moved-from object in
a zombie state that is only valid for destruction and move assignment.
This seems fine to me, and leaving it in the default constructed state
would require adding more state to the object and potentially allocating
memory (!!!) and so seems like a Bad Idea.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245192 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/FoldingSet.h b/include/llvm/ADT/FoldingSet.h
index 42e2e612d561cdfb64aa9477b4b7264fecf40355..c9205396591b89bd3cc8d3141c20218cc9356c62 100644 (file)
--- a/include/llvm/ADT/FoldingSet.h
+++ b/include/llvm/ADT/FoldingSet.h
@@ -122,9 +122,10 @@ protected:
   /// is greater than twice the number of buckets.
   unsigned NumNodes;
 
-  ~FoldingSetImpl();
-
   explicit FoldingSetImpl(unsigned Log2InitSize = 6);
+  FoldingSetImpl(FoldingSetImpl &&Arg);
+  FoldingSetImpl &operator=(FoldingSetImpl &&RHS);
+  ~FoldingSetImpl();
 
 public:
   //===--------------------------------------------------------------------===//
@@ -391,6 +392,10 @@ DefaultContextualFoldingSetTrait<T, Ctx>::ComputeHash(T &X,
 /// implementation of the folding set to the node class T.  T must be a
 /// subclass of FoldingSetNode and implement a Profile function.
 ///
+/// Note that this set type is movable and move-assignable. However, its
+/// moved-from state is not a valid state for anything other than
+/// move-assigning and destroying. This is primarily to enable movable APIs
+/// that incorporate these objects.
 template <class T> class FoldingSet final : public FoldingSetImpl {
 private:
   /// GetNodeProfile - Each instantiatation of the FoldingSet needs to provide a
@@ -415,8 +420,13 @@ private:
 
 public:
   explicit FoldingSet(unsigned Log2InitSize = 6)
-  : FoldingSetImpl(Log2InitSize)
-  {}
+      : FoldingSetImpl(Log2InitSize) {}
+
+  FoldingSet(FoldingSet &&Arg) : FoldingSetImpl(std::move(Arg)) {}
+  FoldingSet &operator=(FoldingSet &&RHS) {
+    (void)FoldingSetImpl::operator=(std::move(RHS));
+    return *this;
+  }
 
   typedef FoldingSetIterator<T> iterator;
   iterator begin() { return iterator(Buckets); }

diff --git a/lib/Support/FoldingSet.cpp b/lib/Support/FoldingSet.cpp
index b8538ffe1f9fe08ba493a9a55401c282f8e4c3c5..bb0ec2defef9f1c761974484cf8cae2b09301281 100644 (file)
--- a/lib/Support/FoldingSet.cpp
+++ b/lib/Support/FoldingSet.cpp
@@ -232,9 +232,29 @@ FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) {
   Buckets = AllocateBuckets(NumBuckets);
   NumNodes = 0;
 }
+
+FoldingSetImpl::FoldingSetImpl(FoldingSetImpl &&Arg)
+    : Buckets(Arg.Buckets), NumBuckets(Arg.NumBuckets), NumNodes(Arg.NumNodes) {
+  Arg.Buckets = nullptr;
+  Arg.NumBuckets = 0;
+  Arg.NumNodes = 0;
+}
+
+FoldingSetImpl &FoldingSetImpl::operator=(FoldingSetImpl &&RHS) {
+  free(Buckets); // This may be null if the set is in a moved-from state.
+  Buckets = RHS.Buckets;
+  NumBuckets = RHS.NumBuckets;
+  NumNodes = RHS.NumNodes;
+  RHS.Buckets = nullptr;
+  RHS.NumBuckets = 0;
+  RHS.NumNodes = 0;
+  return *this;
+}
+
 FoldingSetImpl::~FoldingSetImpl() {
   free(Buckets);
 }
+
 void FoldingSetImpl::clear() {
   // Set all but the last bucket to null pointers.
   memset(Buckets, 0, NumBuckets*sizeof(void*));