[ADT]Add helper function to return a ArrayRef of MapVector's underlying vector (#138726)

mingmingl-llvm · web-flow · commit ad5b3e01fbc8 · 2025-05-06T11:26:53.000-07:00
SetVector currently has a [similar method](https://github.com/llvm/llvm-project/blob/c956ed06dc1c1b340d0c589c472c438b9220b36d/llvm/include/llvm/ADT/SetVector.h#L90), and #138170 has a use case to get an ArrayRef of MapVector's underlying vector.
diff --git a/llvm/include/llvm/ADT/MapVector.h b/llvm/include/llvm/ADT/MapVector.h
@@ -57,6 +57,9 @@ class MapVector {
     return std::move(Vector);
   }
 
+  /// Returns an array reference of the underlying vector.
+  ArrayRef<value_type> getArrayRef() const { return Vector; }
+
   size_type size() const { return Vector.size(); }
 
   /// Grow the MapVector so that it can contain at least \p NumEntries items
diff --git a/llvm/unittests/ADT/MapVectorTest.cpp b/llvm/unittests/ADT/MapVectorTest.cpp
@@ -7,7 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/iterator_range.h"
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <memory>
 #include <utility>
@@ -267,6 +269,29 @@ TEST(MapVectorTest, NonCopyable) {
   ASSERT_EQ(*MV.find(2)->second, 2);
 }
 
+TEST(MapVectorTest, GetArrayRef) {
+  MapVector<int, int> MV;
+
+  // The underlying vector is empty to begin with.
+  EXPECT_TRUE(MV.getArrayRef().empty());
+
+  // Test inserted element.
+  MV.insert(std::make_pair(100, 99));
+  EXPECT_TRUE(MV.getArrayRef().equals({std::pair(100, 99)}));
+
+  // Inserting a different element for an existing key won't change the
+  // underlying vector.
+  auto [Iter, Inserted] = MV.try_emplace(100, 98);
+  EXPECT_FALSE(Inserted);
+  EXPECT_EQ(Iter->second, 99);
+  EXPECT_TRUE(MV.getArrayRef().equals({std::pair(100, 99)}));
+
+  // Inserting a new element. Tests that elements are in order in the underlying
+  // array.
+  MV.insert(std::make_pair(99, 98));
+  EXPECT_TRUE(MV.getArrayRef().equals({std::pair(100, 99), std::pair(99, 98)}));
+}
+
 template <class IntType> struct MapVectorMappedTypeTest : ::testing::Test {
   using int_type = IntType;
 };

Original file line number	Diff line number	Diff line change
`@@ -57,6 +57,9 @@ class MapVector {`
`57`	`57`	`return std::move(Vector);`
`58`	`58`	`}`
`59`	`59`
	`60`	`+ /// Returns an array reference of the underlying vector.`
	`61`	`+ ArrayRef<value_type> getArrayRef() const { return Vector; }`
	`62`	`+`
`60`	`63`	`size_type size() const { return Vector.size(); }`
`61`	`64`
`62`	`65`	`/// Grow the MapVector so that it can contain at least \p NumEntries items`