Add an optional optimization to FoldingSet to allow ID values to be

stored rather than recomputed on each bucket traversal.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75480 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/include/llvm/ADT/FoldingSet.h b/include/llvm/ADT/FoldingSet.h
index 1bcff3d..1465d04 100644
--- a/include/llvm/ADT/FoldingSet.h
+++ b/include/llvm/ADT/FoldingSet.h
@@ -439,6 +439,20 @@ public:
 };
 
 //===----------------------------------------------------------------------===//
+/// FastFoldingSetNode - This is a subclass of FoldingSetNode which stores
+/// a FoldingSetNodeID value rather than requiring the node to recompute it
+/// each time it is needed. This trades space for speed (which can be
+/// significant if the ID is long), and it also permits nodes to drop
+/// information that would otherwise only be required for recomputing an ID.
+class FastFoldingSetNode : public FoldingSetNode {
+  FoldingSetNodeID FastID;
+protected:
+  explicit FastFoldingSetNode(const FoldingSetNodeID &ID) : FastID(ID) {}
+public:
+  void Profile(FoldingSetNodeID& ID) { ID = FastID; }
+};
+
+//===----------------------------------------------------------------------===//
 // Partial specializations of FoldingSetTrait.
 
 template<typename T> struct FoldingSetTrait<T*> {