[ADT] Add an initializer_list constructor to {Small,}DenseSet.

llvm/trunk/include/llvm/ADT/DenseSet.h

 // This file defines the DenseSet and SmallDenseSet classes.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ADT_DENSESET_H
 #define LLVM_ADT_DENSESET_H
 
 #include "llvm/ADT/DenseMap.h"
+#include <initializer_list>
 
 namespace llvm {
 
 namespace detail {
 struct DenseSetEmpty {};
 
 // Use the empty base class trick so we can create a DenseMap where the buckets
 // contain only a single item.

 
 public:
   typedef ValueT key_type;
   typedef ValueT value_type;
   typedef unsigned size_type;
 
   explicit DenseSetImpl(unsigned InitialReserve = 0) : TheMap(InitialReserve) {}
 
+  DenseSetImpl(std::initializer_list<ValueT> Elems)
+      : DenseSetImpl(Elems.size()) {
+    insert(Elems.begin(), Elems.end());
+  }
+
   bool empty() const { return TheMap.empty(); }
   size_type size() const { return TheMap.size(); }
   size_t getMemorySize() const { return TheMap.getMemorySize(); }
 
   /// Grow the DenseSet so that it has at least Size buckets. Will not shrink
   /// the Size of the set.
   void resize(size_t Size) { TheMap.resize(Size); }
 

llvm/trunk/unittests/ADT/DenseSetTest.cpp

typedef ::testing::Types<DenseSet<unsigned, TestDenseSetInfo>,
                          const DenseSet<unsigned, TestDenseSetInfo>,
                          SmallDenseSet<unsigned, 1, TestDenseSetInfo>,
                          SmallDenseSet<unsigned, 4, TestDenseSetInfo>,
                          const SmallDenseSet<unsigned, 4, TestDenseSetInfo>,
                          SmallDenseSet<unsigned, 64, TestDenseSetInfo>>
     DenseSetTestTypes;
 TYPED_TEST_CASE(DenseSetTest, DenseSetTestTypes);
 
+TYPED_TEST(DenseSetTest, InitializerList) {
+  TypeParam set({1, 2, 1, 4});
+  EXPECT_EQ(3u, set.size());
+  EXPECT_EQ(1u, set.count(1));
+  EXPECT_EQ(1u, set.count(2));
+  EXPECT_EQ(1u, set.count(4));
+  EXPECT_EQ(0u, set.count(3));
+}
+
+TYPED_TEST(DenseSetTest, EmptyInitializerList) {
+  TypeParam set({});
+  EXPECT_EQ(0u, set.size());
+  EXPECT_EQ(0u, set.count(0));
+}
+
 TYPED_TEST(DenseSetTest, FindAsTest) {
   auto &set = this->Set;
   // Size tests
   EXPECT_EQ(3u, set.size());
 
   // Normal lookup tests
   EXPECT_EQ(1u, set.count(1));
   EXPECT_EQ(0u, *set.find(0));