diff --git a/llvm/include/llvm/ADT/DenseMap.h b/llvm/include/llvm/ADT/DenseMap.h
--- a/llvm/include/llvm/ADT/DenseMap.h
+++ b/llvm/include/llvm/ADT/DenseMap.h
@@ -141,10 +141,15 @@
     setNumTombstones(0);
   }
 
+  /// Return true if the specified key is in the map, false otherwise.
+  bool contains(const_arg_type_t<KeyT> Val) const {
+    const BucketT *TheBucket;
+    return LookupBucketFor(Val, TheBucket);
+  }
+
   /// Return 1 if the specified key is in the map, 0 otherwise.
   size_type count(const_arg_type_t<KeyT> Val) const {
-    const BucketT *TheBucket;
-    return LookupBucketFor(Val, TheBucket) ? 1 : 0;
+    return contains(Val) ? 1 : 0;
   }
 
   iterator find(const_arg_type_t<KeyT> Val) {
diff --git a/llvm/include/llvm/ADT/MapVector.h b/llvm/include/llvm/ADT/MapVector.h
--- a/llvm/include/llvm/ADT/MapVector.h
+++ b/llvm/include/llvm/ADT/MapVector.h
@@ -140,10 +140,9 @@
     return std::make_pair(begin() + I, false);
   }
 
-  size_type count(const KeyT &Key) const {
-    typename MapType::const_iterator Pos = Map.find(Key);
-    return Pos == Map.end()? 0 : 1;
-  }
+  bool contains(const KeyT &Key) const { return Map.find(Key) != Map.end(); }
+
+  size_type count(const KeyT &Key) const { return contains(Key) ? 1 : 0; }
 
   iterator find(const KeyT &Key) {
     typename MapType::const_iterator Pos = Map.find(Key);
diff --git a/llvm/include/llvm/ADT/StringMap.h b/llvm/include/llvm/ADT/StringMap.h
--- a/llvm/include/llvm/ADT/StringMap.h
+++ b/llvm/include/llvm/ADT/StringMap.h
@@ -249,8 +249,11 @@
   /// if the key is not in the map.
   ValueTy &operator[](StringRef Key) { return try_emplace(Key).first->second; }
 
+  /// contains - Return true if the element is in the map, false otherwise.
+  bool contains(StringRef Key) const { return find(Key) != end(); }
+
   /// count - Return 1 if the element is in the map, 0 otherwise.
-  size_type count(StringRef Key) const { return find(Key) == end() ? 0 : 1; }
+  size_type count(StringRef Key) const { return contains(Key) ? 1 : 0; }
 
   template <typename InputTy>
   size_type count(const StringMapEntry<InputTy> &MapEntry) const {
diff --git a/llvm/unittests/ADT/DenseMapTest.cpp b/llvm/unittests/ADT/DenseMapTest.cpp
--- a/llvm/unittests/ADT/DenseMapTest.cpp
+++ b/llvm/unittests/ADT/DenseMapTest.cpp
@@ -122,6 +122,7 @@
 
   // Lookup tests
   EXPECT_FALSE(this->Map.count(this->getKey()));
+  EXPECT_FALSE(this->Map.contains(this->getKey()));
   EXPECT_TRUE(this->Map.find(this->getKey()) == this->Map.end());
   EXPECT_EQ(typename TypeParam::mapped_type(),
             this->Map.lookup(this->getKey()));
@@ -153,6 +154,7 @@
 
   // Lookup tests
   EXPECT_TRUE(this->Map.count(this->getKey()));
+  EXPECT_TRUE(this->Map.contains(this->getKey()));
   EXPECT_TRUE(this->Map.find(this->getKey()) == this->Map.begin());
   EXPECT_EQ(this->getValue(), this->Map.lookup(this->getKey()));
   EXPECT_EQ(this->getValue(), this->Map[this->getKey()]);
diff --git a/llvm/unittests/ADT/MapVectorTest.cpp b/llvm/unittests/ADT/MapVectorTest.cpp
--- a/llvm/unittests/ADT/MapVectorTest.cpp
+++ b/llvm/unittests/ADT/MapVectorTest.cpp
@@ -87,8 +87,10 @@
   MV.insert(std::make_pair(5, 6));
   ASSERT_EQ(MV.size(), 3u);
 
+  ASSERT_TRUE(MV.contains(1));
   MV.erase(MV.find(1));
   ASSERT_EQ(MV.size(), 2u);
+  ASSERT_FALSE(MV.contains(1));
   ASSERT_EQ(MV.find(1), MV.end());
   ASSERT_EQ(MV[3], 4);
   ASSERT_EQ(MV[5], 6);
diff --git a/llvm/unittests/ADT/StringMapTest.cpp b/llvm/unittests/ADT/StringMapTest.cpp
--- a/llvm/unittests/ADT/StringMapTest.cpp
+++ b/llvm/unittests/ADT/StringMapTest.cpp
@@ -41,6 +41,7 @@
     EXPECT_TRUE(testMap.begin() == testMap.end());
 
     // Lookup tests
+    EXPECT_FALSE(testMap.contains(testKey));
     EXPECT_EQ(0u, testMap.count(testKey));
     EXPECT_EQ(0u, testMap.count(StringRef(testKeyFirst, testKeyLength)));
     EXPECT_EQ(0u, testMap.count(testKeyStr));
@@ -64,6 +65,7 @@
     EXPECT_TRUE(it == testMap.end());
 
     // Lookup tests
+    EXPECT_TRUE(testMap.contains(testKey));
     EXPECT_EQ(1u, testMap.count(testKey));
     EXPECT_EQ(1u, testMap.count(StringRef(testKeyFirst, testKeyLength)));
     EXPECT_EQ(1u, testMap.count(testKeyStr));