[ADT] Enable reverse iteration for DenseMap

Reviewers: mehdi_amini, dexonsmith, dblaikie, davide, chandlerc, davidxl, echristo, efriedma

Reviewed By: dblaikie

Subscribers: rsmith, mgorny, emaste, llvm-commits

Differential Revision: https://reviews.llvm.org/D35043

llvm-svn: 311730

1 files changed, 111 insertions, 0 deletions

diff --git a/llvm/unittests/Support/ReverseIterationTest.cpp b/llvm/unittests/Support/ReverseIterationTest.cpp
new file mode 100644
index 00000000000..486c928e47f
--- /dev/null
+++ b/llvm/unittests/Support/ReverseIterationTest.cpp
@@ -0,0 +1,111 @@
+//===- llvm/unittest/Support/ReverseIterationTest.cpp ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+//
+// Reverse Iteration unit tests.
+//
+//===---------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/ReverseIteration.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(ReverseIterationTest, DenseMapTest1) {
+  static_assert(detail::IsPointerLike<int *>::value,
+                "int * is pointer-like");
+  static_assert(detail::IsPointerLike<uintptr_t>::value,
+                "uintptr_t is pointer-like");
+  struct IncompleteType;
+  static_assert(detail::IsPointerLike<IncompleteType *>::value,
+                "incomplete * is pointer-like");
+
+  // Test reverse iteration for a DenseMap with pointer-like keys.
+  // DenseMap should reverse iterate if its keys are pointer-like.
+  DenseMap<int *, int> Map;
+  int a = 1, b = 2, c = 3, d = 4;
+  int *Keys[] = { &a, &b, &c, &d };
+
+  // Insert keys into the DenseMap.
+  for (auto *Key: Keys)
+    Map[Key] = 0;
+
+  // Note: This is the observed order of keys in the DenseMap.
+  // If there is any change in the behavior of the DenseMap, this order would
+  // need to be adjusted accordingly.
+  int *IterKeys[] = { &a, &b, &c, &d };
+  if (shouldReverseIterate<int *>())
+    std::reverse(&IterKeys[0], &IterKeys[4]);
+
+  // Check that the DenseMap is iterated in the expected order.
+  for (const auto &Tuple : zip(Map, IterKeys))
+    ASSERT_EQ(*(std::get<0>(Tuple).first), *(std::get<1>(Tuple)));
+
+  // Check operator++ (post-increment).
+  int i = 0;
+  for (auto iter = Map.begin(), end = Map.end(); iter != end; iter++, ++i)
+    ASSERT_EQ(iter->first, IterKeys[i]);
+}
+
+TEST(ReverseIterationTest, DenseMapTest2) {
+  static_assert(!detail::IsPointerLike<int>::value,
+                "int is not pointer-like");
+
+  // For a DenseMap with non-pointer-like keys, forward iteration equals
+  // reverse iteration.
+  DenseMap<int, int> Map;
+  int Keys[] = { 1, 2, 3, 4 };
+
+  // Insert keys into the DenseMap.
+  for (auto Key: Keys)
+    Map[Key] = 0;
+
+  // Note: This is the observed order of keys in the DenseMap.
+  // If there is any change in the behavior of the DenseMap, this order
+  // would need to be adjusted accordingly.
+  int IterKeys[] = { 2, 4, 1, 3 };
+
+  // Check that the DenseMap is iterated in the expected order.
+  for (const auto &Tuple : zip(Map, IterKeys))
+    ASSERT_EQ(std::get<0>(Tuple).first, std::get<1>(Tuple));
+
+  // Check operator++ (post-increment).
+  int i = 0;
+  for (auto iter = Map.begin(), end = Map.end(); iter != end; iter++, ++i)
+    ASSERT_EQ(iter->first, IterKeys[i]);
+}
+
+TEST(ReverseIterationTest, SmallPtrSetTest) {
+  static_assert(detail::IsPointerLike<void *>::value,
+                "void * is pointer-like");
+
+  SmallPtrSet<void *, 4> Set;
+  int a = 1, b = 2, c = 3, d = 4;
+  int *Ptrs[] = { &a, &b, &c, &d };
+
+  for (auto *Ptr: Ptrs)
+    Set.insert(Ptr);
+
+  // Note: This is the observed order of keys in the SmallPtrSet.
+  // If there is any change in the behavior of the SmallPtrSet, this order
+  // would need to be adjusted accordingly.
+  int *IterPtrs[] = { &a, &b, &c, &d };
+  if (shouldReverseIterate<int *>())
+    std::reverse(&IterPtrs[0], &IterPtrs[4]);
+
+  // Check that the SmallPtrSet is iterated in the expected order.
+  for (const auto &Tuple : zip(Set, IterPtrs))
+    ASSERT_EQ(std::get<0>(Tuple), std::get<1>(Tuple));
+
+  // Check operator++ (post-increment).
+  int i = 0;
+  for (auto iter = Set.begin(), end = Set.end(); iter != end; iter++, ++i)
+    ASSERT_EQ(*iter, IterPtrs[i]);
+}