diff --git a/llvm/include/llvm/ADT/DenseSet.h b/llvm/include/llvm/ADT/DenseSet.h
--- a/llvm/include/llvm/ADT/DenseSet.h
+++ b/llvm/include/llvm/ADT/DenseSet.h
@@ -173,6 +173,11 @@
     return ConstIterator(TheMap.find(V));
   }
 
+  /// Check if the set contains the given element.
+  bool contains(const_arg_type_t<ValueT> V) const {
+    return TheMap.find(V) != TheMap.end();
+  }
+
   /// Alternative version of find() which allows a different, and possibly less
   /// expensive, key type.
   /// The DenseMapInfo is responsible for supplying methods
diff --git a/llvm/include/llvm/ADT/SetVector.h b/llvm/include/llvm/ADT/SetVector.h
--- a/llvm/include/llvm/ADT/SetVector.h
+++ b/llvm/include/llvm/ADT/SetVector.h
@@ -205,6 +205,11 @@
     return true;
   }
 
+  /// Check if the SetVector contains the given key.
+  bool contains(const key_type &key) const {
+    return set_.find(key) != set_.end();
+  }
+
   /// Count the number of elements of a given key in the SetVector.
   /// \returns 0 if the element is not in the SetVector, 1 if it is.
   size_type count(const key_type &key) const {
diff --git a/llvm/include/llvm/ADT/SmallPtrSet.h b/llvm/include/llvm/ADT/SmallPtrSet.h
--- a/llvm/include/llvm/ADT/SmallPtrSet.h
+++ b/llvm/include/llvm/ADT/SmallPtrSet.h
@@ -378,6 +378,9 @@
   iterator find(ConstPtrType Ptr) const {
     return makeIterator(find_imp(ConstPtrTraits::getAsVoidPointer(Ptr)));
   }
+  bool contains(ConstPtrType Ptr) const {
+    return find_imp(ConstPtrTraits::getAsVoidPointer(Ptr)) != EndPointer();
+  }
 
   template <typename IterT>
   void insert(IterT I, IterT E) {
diff --git a/llvm/include/llvm/ADT/SmallSet.h b/llvm/include/llvm/ADT/SmallSet.h
--- a/llvm/include/llvm/ADT/SmallSet.h
+++ b/llvm/include/llvm/ADT/SmallSet.h
@@ -232,6 +232,12 @@
     return {Set.end()};
   }
 
+  bool contains(const T &V) const {
+    if (isSmall())
+      return vfind(V) != Vector.end();
+    return Set.find(V) != Set.end();
+  }
+
 private:
   bool isSmall() const { return Set.empty(); }
 
diff --git a/llvm/include/llvm/ADT/SparseSet.h b/llvm/include/llvm/ADT/SparseSet.h
--- a/llvm/include/llvm/ADT/SparseSet.h
+++ b/llvm/include/llvm/ADT/SparseSet.h
@@ -229,11 +229,18 @@
     return const_cast<SparseSet*>(this)->findIndex(KeyIndexOf(Key));
   }
 
+  /// Check if the given key is present in the set.
+  ///
+  /// @param Key A valid key to find.
+  bool contains(const KeyT &Key) const {
+    return find(Key) == end() ? 0 : 1;
+  }
+
   /// count - Returns 1 if this set contains an element identified by Key,
   /// 0 otherwise.
   ///
   size_type count(const KeyT &Key) const {
-    return find(Key) == end() ? 0 : 1;
+    return contains(Key) ? 1 : 0;
   }
 
   /// insert - Attempts to insert a new element.
diff --git a/llvm/include/llvm/ADT/StringSet.h b/llvm/include/llvm/ADT/StringSet.h
--- a/llvm/include/llvm/ADT/StringSet.h
+++ b/llvm/include/llvm/ADT/StringSet.h
@@ -45,6 +45,10 @@
   insert(const StringMapEntry<ValueTy> &mapEntry) {
     return insert(mapEntry.getKey());
   }
+
+  bool contains(StringRef key) const {
+    return Base::FindKey(key) != -1;
+  }
 };
 
 } // end namespace llvm