[ADT] Add more useful methods to SmallSet API (#108601)

This patch adds useful methods to the SmallSet API:

 - Constructor that takes pair of iterators.
 - Constructor that takes a range.
 - Constructor that takes an initializer list.
 - Copy constructor.
 - Move constructor.
 - Copy assignment operator.
 - Move assignment operator.

Author: vhscampos

llvm/include/llvm/ADT/SmallSet.h

@@ -19,6 +19,7 @@
 #include "llvm/ADT/iterator.h"
 #include <cstddef>
 #include <functional>
+#include <initializer_list>
 #include <set>
 #include <utility>
 
@@ -147,6 +148,22 @@ class SmallSet {
   using const_iterator = SmallSetIterator<T, N, C>;
 
   SmallSet() = default;
+  SmallSet(const SmallSet &) = default;
+  SmallSet(SmallSet &&) = default;
+
+  template <typename IterT> SmallSet(IterT Begin, IterT End) {
+    insert(Begin, End);
+  }
+
+  template <typename RangeT>
+  explicit SmallSet(const iterator_range<RangeT> &R) {
+    insert(R.begin(), R.end());
+  }
+
+  SmallSet(std::initializer_list<T> L) { insert(L.begin(), L.end()); }
+
+  SmallSet &operator=(const SmallSet &) = default;
+  SmallSet &operator=(SmallSet &&) = default;
 
   [[nodiscard]] bool empty() const { return Vector.empty() && Set.empty(); }
 

llvm/unittests/ADT/SmallSetTest.cpp

@@ -12,11 +12,63 @@
 
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/STLExtras.h"
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <string>
 
 using namespace llvm;
 
+TEST(SmallSetTest, ConstructorIteratorPair) {
+  std::initializer_list<int> L = {1, 2, 3, 4, 5};
+  SmallSet<int, 4> S(std::begin(L), std::end(L));
+  EXPECT_THAT(S, testing::UnorderedElementsAreArray(L));
+}
+
+TEST(SmallSet, ConstructorRange) {
+  std::initializer_list<int> L = {1, 2, 3, 4, 5};
+
+  SmallSet<int, 4> S(llvm::make_range(std::begin(L), std::end(L)));
+  EXPECT_THAT(S, testing::UnorderedElementsAreArray(L));
+}
+
+TEST(SmallSet, ConstructorInitializerList) {
+  std::initializer_list<int> L = {1, 2, 3, 4, 5};
+  SmallSet<int, 4> S = {1, 2, 3, 4, 5};
+  EXPECT_THAT(S, testing::UnorderedElementsAreArray(L));
+}
+
+TEST(SmallSet, CopyConstructor) {
+  SmallSet<int, 4> S = {1, 2, 3};
+  SmallSet<int, 4> T = S;
+
+  EXPECT_THAT(S, testing::ContainerEq(T));
+}
+
+TEST(SmallSet, MoveConstructor) {
+  std::initializer_list<int> L = {1, 2, 3};
+  SmallSet<int, 4> S = L;
+  SmallSet<int, 4> T = std::move(S);
+
+  EXPECT_THAT(T, testing::UnorderedElementsAreArray(L));
+}
+
+TEST(SmallSet, CopyAssignment) {
+  SmallSet<int, 4> S = {1, 2, 3};
+  SmallSet<int, 4> T;
+  T = S;
+
+  EXPECT_THAT(S, testing::ContainerEq(T));
+}
+
+TEST(SmallSet, MoveAssignment) {
+  std::initializer_list<int> L = {1, 2, 3};
+  SmallSet<int, 4> S = L;
+  SmallSet<int, 4> T;
+  T = std::move(S);
+
+  EXPECT_THAT(T, testing::UnorderedElementsAreArray(L));
+}
+
 TEST(SmallSetTest, Insert) {
 
   SmallSet<int, 4> s1;