[DenseMap] Introduce keys, values iterators (#138848)

Author: artagnon

llvm/include/llvm/ADT/DenseMap.h

@@ -17,6 +17,7 @@
 #include "llvm/ADT/ADL.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/EpochTracker.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/AlignOf.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MathExtras.h"
@@ -96,6 +97,24 @@ class DenseMapBase : public DebugEpochBase {
     return makeConstIterator(getBucketsEnd(), getBucketsEnd(), *this, true);
   }
 
+  // Return an iterator to iterate over keys in the map.
+  inline auto keys() {
+    return map_range(*this, [](const BucketT &P) { return P.getFirst(); });
+  }
+
+  // Return an iterator to iterate over values in the map.
+  inline auto values() {
+    return map_range(*this, [](const BucketT &P) { return P.getSecond(); });
+  }
+
+  inline auto keys() const {
+    return map_range(*this, [](const BucketT &P) { return P.getFirst(); });
+  }
+
+  inline auto values() const {
+    return map_range(*this, [](const BucketT &P) { return P.getSecond(); });
+  }
+
   [[nodiscard]] bool empty() const { return getNumEntries() == 0; }
   unsigned size() const { return getNumEntries(); }
 

llvm/unittests/ADT/DenseMapTest.cpp

@@ -10,6 +10,7 @@
 #include "CountCopyAndMove.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/DenseMapInfoVariant.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
@@ -359,6 +360,51 @@ TYPED_TEST(DenseMapTest, ConstIteratorTest) {
   EXPECT_TRUE(cit == cit2);
 }
 
+TYPED_TEST(DenseMapTest, KeysValuesIterator) {
+  SmallSet<typename TypeParam::key_type, 10> Keys;
+  SmallSet<typename TypeParam::mapped_type, 10> Values;
+  for (int I = 0; I < 10; ++I) {
+    auto K = this->getKey(I);
+    auto V = this->getValue(I);
+    Keys.insert(K);
+    Values.insert(V);
+    this->Map[K] = V;
+  }
+
+  SmallSet<typename TypeParam::key_type, 10> ActualKeys;
+  SmallSet<typename TypeParam::mapped_type, 10> ActualValues;
+  for (auto K : this->Map.keys())
+    ActualKeys.insert(K);
+  for (auto V : this->Map.values())
+    ActualValues.insert(V);
+
+  EXPECT_EQ(Keys, ActualKeys);
+  EXPECT_EQ(Values, ActualValues);
+}
+
+TYPED_TEST(DenseMapTest, ConstKeysValuesIterator) {
+  SmallSet<typename TypeParam::key_type, 10> Keys;
+  SmallSet<typename TypeParam::mapped_type, 10> Values;
+  for (int I = 0; I < 10; ++I) {
+    auto K = this->getKey(I);
+    auto V = this->getValue(I);
+    Keys.insert(K);
+    Values.insert(V);
+    this->Map[K] = V;
+  }
+
+  const TypeParam &ConstMap = this->Map;
+  SmallSet<typename TypeParam::key_type, 10> ActualKeys;
+  SmallSet<typename TypeParam::mapped_type, 10> ActualValues;
+  for (auto K : ConstMap.keys())
+    ActualKeys.insert(K);
+  for (auto V : ConstMap.values())
+    ActualValues.insert(V);
+
+  EXPECT_EQ(Keys, ActualKeys);
+  EXPECT_EQ(Values, ActualValues);
+}
+
 // Test initializer list construction.
 TEST(DenseMapCustomTest, InitializerList) {
   DenseMap<int, int> M({{0, 0}, {0, 1}, {1, 2}});