[Support] Recycler: Implement move constructor

llvm/include/llvm/Support/Recycler.h

@@ -60,6 +60,10 @@ class Recycler {
     // clear() before deleting the Recycler.
     assert(!FreeList && "Non-empty recycler deleted!");
   }
+  Recycler(const Recycler &) = delete;
+  Recycler(Recycler &&Other)
+      : FreeList(std::exchange(Other.FreeList, nullptr)) {}
+  Recycler() = default;
 
   /// clear - Release all the tracked allocations to the allocator. The
   /// recycler must be free of any tracked allocations before being

llvm/unittests/Support/CMakeLists.txt

@@ -69,6 +69,7 @@ add_llvm_unittest(SupportTests
   PerThreadBumpPtrAllocatorTest.cpp
   ProcessTest.cpp
   ProgramTest.cpp
+  RecyclerTest.cpp
   RegexTest.cpp
   ReverseIterationTest.cpp
   ReplaceFileTest.cpp

llvm/unittests/Support/RecyclerTest.cpp

@@ -0,0 +1,47 @@
+//===--- unittest/Support/RecyclerTest.cpp --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Recycler.h"
+#include "llvm/Support/AllocatorBase.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+struct Object8 {
+  char Data[8];
+};
+
+class DecoratedMallocAllocator : public MallocAllocator {
+public:
+  int DeallocCount = 0;
+
+  template <typename T> void Deallocate(T *Ptr) {
+    DeallocCount++;
+    MallocAllocator::Deallocate(Ptr);
+  }
+};
+
+TEST(RecyclerTest, MoveConstructor) {
+  DecoratedMallocAllocator Allocator;
+  Recycler<Object8> R;
+  Object8 *A1 = R.Allocate(Allocator);
+  Object8 *A2 = R.Allocate(Allocator);
+  R.Deallocate(Allocator, A1);
+  R.Deallocate(Allocator, A2);
+  Recycler<Object8> R2(std::move(R));
+  Object8 *A3 = R2.Allocate(Allocator);
+  R2.Deallocate(Allocator, A3);
+  R.clear(Allocator); // Should not deallocate anything as it was moved from.
+  EXPECT_EQ(Allocator.DeallocCount, 0);
+  R2.clear(Allocator);
+  EXPECT_EQ(Allocator.DeallocCount, 2);
+}
+
+} // end anonymous namespace