[unittests] Add reverse iteration unit test for pointer-like keys

Reviewers: dblaikie, efriedma, mehdi_amini

Reviewed By: dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37241

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312574 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Support/ReverseIterationTest.cpp

@@ -53,3 +53,53 @@ TEST(ReverseIterationTest, DenseMapTest1) {
   for (auto iter = Map.begin(), end = Map.end(); iter != end; iter++, ++i)
     ASSERT_EQ(iter->first, IterKeys[i]);
 }
+
+// Define a pointer-like int.
+struct PtrLikeInt { int value; };
+
+template<> struct DenseMapInfo<PtrLikeInt *> {
+  static PtrLikeInt *getEmptyKey() {
+    static PtrLikeInt EmptyKey;
+    return &EmptyKey;
+  }
+
+  static PtrLikeInt *getTombstoneKey() {
+    static PtrLikeInt TombstoneKey;
+    return &TombstoneKey;
+  }
+
+  static int getHashValue(const PtrLikeInt *P) {
+    return P->value;
+  }
+
+  static bool isEqual(const PtrLikeInt *LHS, const PtrLikeInt *RHS) {
+    return LHS == RHS;
+  }
+};
+
+TEST(ReverseIterationTest, DenseMapTest2) {
+  static_assert(detail::IsPointerLike<PtrLikeInt *>::value,
+                "PtrLikeInt * is pointer-like");
+
+  PtrLikeInt a = {4}, b = {8}, c = {12}, d = {16};
+  PtrLikeInt *Keys[] = { &a, &b, &c, &d };
+
+  // Insert keys into the DenseMap.
+  DenseMap<PtrLikeInt *, int> Map;
+  for (auto *Key : Keys)
+    Map[Key] = Key->value;
+
+  // Note: If there is any change in the behavior of the DenseMap,
+  // the observed order of keys would need to be adjusted accordingly.
+  if (shouldReverseIterate<PtrLikeInt *>())
+    std::reverse(&Keys[0], &Keys[4]);
+
+  // Check that the DenseMap is iterated in the expected order.
+  for (const auto &Tuple : zip(Map, Keys))
+    ASSERT_EQ(std::get<0>(Tuple).second, std::get<1>(Tuple)->value);
+
+  // Check operator++ (post-increment).
+  int i = 0;
+  for (auto iter = Map.begin(), end = Map.end(); iter != end; iter++, ++i)
+    ASSERT_EQ(iter->second, Keys[i]->value);
+}