[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.

llvm-svn: 245192

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Support/FoldingSet.cpp b/llvm/lib/Support/FoldingSet.cpp
index b8538ffe1f9..bb0ec2defef 100644
--- a/llvm/lib/Support/FoldingSet.cpp
+++ b/llvm/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*));