v8/test/unittests/heap/cppgc/write-barrier-unittest.cc

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "include/cppgc/internal/write-barrier.h"

#include <algorithm>
#include <initializer_list>
#include <vector>

#include "include/cppgc/heap-consistency.h"
#include "include/cppgc/internal/pointer-policies.h"
#include "src/base/logging.h"
#include "src/heap/cppgc/heap-object-header.h"
#include "src/heap/cppgc/marker.h"
#include "test/unittests/heap/cppgc/tests.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace cppgc {
namespace internal {

namespace {

class V8_NODISCARD IncrementalMarkingScope {
 public:
  explicit IncrementalMarkingScope(MarkerBase* marker) : marker_(marker) {}

  ~IncrementalMarkingScope() V8_NOEXCEPT {
    marker_->FinishMarking(kIncrementalConfig.stack_state);
  }

  static constexpr Marker::MarkingConfig kIncrementalConfig{
      Marker::MarkingConfig::CollectionType::kMajor,
      Marker::MarkingConfig::StackState::kNoHeapPointers,
      Marker::MarkingConfig::MarkingType::kIncremental};

 private:
  MarkerBase* marker_;
};

constexpr Marker::MarkingConfig IncrementalMarkingScope::kIncrementalConfig;

class V8_NODISCARD ExpectWriteBarrierFires final
    : private IncrementalMarkingScope {
 public:
  ExpectWriteBarrierFires(MarkerBase* marker,
                          std::initializer_list<void*> objects)
      : IncrementalMarkingScope(marker),
        marking_worklist_(
            marker->MutatorMarkingStateForTesting().marking_worklist()),
        write_barrier_worklist_(
            marker->MutatorMarkingStateForTesting().write_barrier_worklist()),
        retrace_marked_objects_worklist_(
            marker->MutatorMarkingStateForTesting()
                .retrace_marked_objects_worklist()),
        objects_(objects) {
    EXPECT_TRUE(marking_worklist_.IsGlobalEmpty());
    EXPECT_TRUE(write_barrier_worklist_.IsGlobalEmpty());
    for (void* object : objects) {
      headers_.push_back(&HeapObjectHeader::FromObject(object));
      EXPECT_FALSE(headers_.back()->IsMarked());
    }
  }

  ~ExpectWriteBarrierFires() V8_NOEXCEPT {
    {
      MarkingWorklists::MarkingItem item;
      while (marking_worklist_.Pop(&item)) {
        auto pos = std::find(objects_.begin(), objects_.end(),
                             item.base_object_payload);
        if (pos != objects_.end()) objects_.erase(pos);
      }
    }
    {
      HeapObjectHeader* item;
      while (write_barrier_worklist_.Pop(&item)) {
        auto pos =
            std::find(objects_.begin(), objects_.end(), item->ObjectStart());
        if (pos != objects_.end()) objects_.erase(pos);
      }
    }
    {
      HeapObjectHeader* item;
      while (retrace_marked_objects_worklist_.Pop(&item)) {
        auto pos =
            std::find(objects_.begin(), objects_.end(), item->ObjectStart());
        if (pos != objects_.end()) objects_.erase(pos);
      }
    }
    EXPECT_TRUE(objects_.empty());
    for (auto* header : headers_) {
      EXPECT_TRUE(header->IsMarked());
      header->Unmark();
    }
    EXPECT_TRUE(marking_worklist_.IsGlobalEmpty());
    EXPECT_TRUE(write_barrier_worklist_.IsGlobalEmpty());
  }

 private:
  MarkingWorklists::MarkingWorklist::Local& marking_worklist_;
  MarkingWorklists::WriteBarrierWorklist::Local& write_barrier_worklist_;
  MarkingWorklists::RetraceMarkedObjectsWorklist::Local&
      retrace_marked_objects_worklist_;
  std::vector<void*> objects_;
  std::vector<HeapObjectHeader*> headers_;
};

class V8_NODISCARD ExpectNoWriteBarrierFires final
    : private IncrementalMarkingScope {
 public:
  ExpectNoWriteBarrierFires(MarkerBase* marker,
                            std::initializer_list<void*> objects)
      : IncrementalMarkingScope(marker),
        marking_worklist_(
            marker->MutatorMarkingStateForTesting().marking_worklist()),
        write_barrier_worklist_(
            marker->MutatorMarkingStateForTesting().write_barrier_worklist()) {
    EXPECT_TRUE(marking_worklist_.IsGlobalEmpty());
    EXPECT_TRUE(write_barrier_worklist_.IsGlobalEmpty());
    for (void* object : objects) {
      auto* header = &HeapObjectHeader::FromObject(object);
      headers_.emplace_back(header, header->IsMarked());
    }
  }

  ~ExpectNoWriteBarrierFires() {
    EXPECT_TRUE(marking_worklist_.IsGlobalEmpty());
    EXPECT_TRUE(write_barrier_worklist_.IsGlobalEmpty());
    for (const auto& pair : headers_) {
      EXPECT_EQ(pair.second, pair.first->IsMarked());
    }
  }

 private:
  MarkingWorklists::MarkingWorklist::Local& marking_worklist_;
  MarkingWorklists::WriteBarrierWorklist::Local& write_barrier_worklist_;
  std::vector<std::pair<HeapObjectHeader*, bool /* was marked */>> headers_;
};

class GCed : public GarbageCollected<GCed> {
 public:
  GCed() = default;
  explicit GCed(GCed* next) : next_(next) {}

  void Trace(cppgc::Visitor* v) const { v->Trace(next_); }

  bool IsMarked() const {
    return HeapObjectHeader::FromObject(this).IsMarked();
  }

  void set_next(GCed* next) { next_ = next; }
  GCed* next() const { return next_; }
  Member<GCed>& next_ref() { return next_; }

 private:
  Member<GCed> next_ = nullptr;
};

}  // namespace

class WriteBarrierTest : public testing::TestWithHeap {
 public:
  WriteBarrierTest() : internal_heap_(Heap::From(GetHeap())) {
    DCHECK_NULL(GetMarkerRef().get());
    GetMarkerRef() =
        std::make_unique<Marker>(*internal_heap_, GetPlatformHandle().get(),
                                 IncrementalMarkingScope::kIncrementalConfig);
    marker_ = GetMarkerRef().get();
    marker_->StartMarking();
  }

  ~WriteBarrierTest() override {
    marker_->ClearAllWorklistsForTesting();
    GetMarkerRef().reset();
  }

  MarkerBase* marker() const { return marker_; }

 private:
  Heap* internal_heap_;
  MarkerBase* marker_;
};

class NoWriteBarrierTest : public testing::TestWithHeap {};

// =============================================================================
// Basic support. ==============================================================
// =============================================================================

TEST_F(WriteBarrierTest, EnableDisableIncrementalMarking) {
  {
    IncrementalMarkingScope scope(marker());
    EXPECT_TRUE(WriteBarrier::IsEnabled());
  }
}

TEST_F(WriteBarrierTest, TriggersWhenMarkingIsOn) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  {
    ExpectWriteBarrierFires scope(marker(), {object1});
    EXPECT_FALSE(object1->IsMarked());
    object2->set_next(object1);
    EXPECT_TRUE(object1->IsMarked());
  }
}

TEST_F(NoWriteBarrierTest, BailoutWhenMarkingIsOff) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  EXPECT_FALSE(object1->IsMarked());
  object2->set_next(object1);
  EXPECT_FALSE(object1->IsMarked());
}

TEST_F(WriteBarrierTest, BailoutIfMarked) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  EXPECT_TRUE(HeapObjectHeader::FromObject(object1).TryMarkAtomic());
  {
    ExpectNoWriteBarrierFires scope(marker(), {object1});
    object2->set_next(object1);
  }
}

TEST_F(WriteBarrierTest, MemberInitializingStoreNoBarrier) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  {
    ExpectNoWriteBarrierFires scope(marker(), {object1});
    auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
    HeapObjectHeader& object2_header = HeapObjectHeader::FromObject(object2);
    EXPECT_FALSE(object2_header.IsMarked());
  }
}

TEST_F(WriteBarrierTest, MemberReferenceAssignMember) {
  auto* obj = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* ref_obj = MakeGarbageCollected<GCed>(GetAllocationHandle());
  Member<GCed>& m2 = ref_obj->next_ref();
  Member<GCed> m3(obj);
  {
    ExpectWriteBarrierFires scope(marker(), {obj});
    m2 = m3;
  }
}

TEST_F(WriteBarrierTest, MemberSetSentinelValueNoBarrier) {
  auto* obj = MakeGarbageCollected<GCed>(GetAllocationHandle());
  Member<GCed>& m = obj->next_ref();
  {
    ExpectNoWriteBarrierFires scope(marker(), {});
    m = kSentinelPointer;
  }
}

TEST_F(WriteBarrierTest, MemberCopySentinelValueNoBarrier) {
  auto* obj1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  Member<GCed>& m1 = obj1->next_ref();
  m1 = kSentinelPointer;
  {
    ExpectNoWriteBarrierFires scope(marker(), {});
    auto* obj2 = MakeGarbageCollected<GCed>(GetAllocationHandle());
    obj2->next_ref() = m1;
  }
}

// =============================================================================
// Mixin support. ==============================================================
// =============================================================================

namespace {

class Mixin : public GarbageCollectedMixin {
 public:
  void Trace(cppgc::Visitor* visitor) const override { visitor->Trace(next_); }

  virtual void Bar() {}

 protected:
  Member<GCed> next_;
};

class ClassWithVirtual {
 protected:
  virtual void Foo() {}
};

class Child : public GarbageCollected<Child>,
              public ClassWithVirtual,
              public Mixin {
 public:
  Child() : ClassWithVirtual(), Mixin() {}
  ~Child() = default;

  void Trace(cppgc::Visitor* visitor) const override { Mixin::Trace(visitor); }

  void Foo() override {}
  void Bar() override {}
};

class ParentWithMixinPointer : public GarbageCollected<ParentWithMixinPointer> {
 public:
  ParentWithMixinPointer() = default;

  void set_mixin(Mixin* mixin) { mixin_ = mixin; }

  virtual void Trace(cppgc::Visitor* visitor) const { visitor->Trace(mixin_); }

 protected:
  Member<Mixin> mixin_;
};

}  // namespace

TEST_F(WriteBarrierTest, WriteBarrierOnUnmarkedMixinApplication) {
  ParentWithMixinPointer* parent =
      MakeGarbageCollected<ParentWithMixinPointer>(GetAllocationHandle());
  auto* child = MakeGarbageCollected<Child>(GetAllocationHandle());
  Mixin* mixin = static_cast<Mixin*>(child);
  EXPECT_NE(static_cast<void*>(child), static_cast<void*>(mixin));
  {
    ExpectWriteBarrierFires scope(marker(), {child});
    parent->set_mixin(mixin);
  }
}

TEST_F(WriteBarrierTest, NoWriteBarrierOnMarkedMixinApplication) {
  ParentWithMixinPointer* parent =
      MakeGarbageCollected<ParentWithMixinPointer>(GetAllocationHandle());
  auto* child = MakeGarbageCollected<Child>(GetAllocationHandle());
  EXPECT_TRUE(HeapObjectHeader::FromObject(child).TryMarkAtomic());
  Mixin* mixin = static_cast<Mixin*>(child);
  EXPECT_NE(static_cast<void*>(child), static_cast<void*>(mixin));
  {
    ExpectNoWriteBarrierFires scope(marker(), {child});
    parent->set_mixin(mixin);
  }
}

// =============================================================================
// Raw barriers. ===============================================================
// =============================================================================

using WriteBarrierParams = subtle::HeapConsistency::WriteBarrierParams;
using WriteBarrierType = subtle::HeapConsistency::WriteBarrierType;
using subtle::HeapConsistency;

TEST_F(NoWriteBarrierTest, WriteBarrierBailoutWhenMarkingIsOff) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
  {
    EXPECT_FALSE(object1->IsMarked());
    WriteBarrierParams params;
    const WriteBarrierType expected =
        Heap::From(GetHeap())->generational_gc_supported()
            ? WriteBarrierType::kGenerational
            : WriteBarrierType::kNone;
    EXPECT_EQ(expected, HeapConsistency::GetWriteBarrierType(
                            object2->next_ref().GetSlotForTesting(),
                            object2->next_ref().Get(), params));
    EXPECT_FALSE(object1->IsMarked());
  }
}

TEST_F(WriteBarrierTest, DijkstraWriteBarrierTriggersWhenMarkingIsOn) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
  {
    ExpectWriteBarrierFires scope(marker(), {object1});
    EXPECT_FALSE(object1->IsMarked());
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  object2->next_ref().GetSlotForTesting(),
                  object2->next_ref().Get(), params));
    HeapConsistency::DijkstraWriteBarrier(params, object2->next_ref().Get());
    EXPECT_TRUE(object1->IsMarked());
  }
}

TEST_F(WriteBarrierTest, DijkstraWriteBarrierBailoutIfMarked) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
  EXPECT_TRUE(HeapObjectHeader::FromObject(object1).TryMarkAtomic());
  {
    ExpectNoWriteBarrierFires scope(marker(), {object1});
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  object2->next_ref().GetSlotForTesting(),
                  object2->next_ref().Get(), params));
    HeapConsistency::DijkstraWriteBarrier(params, object2->next_ref().Get());
  }
}

namespace {

struct InlinedObject {
  void Trace(cppgc::Visitor* v) const { v->Trace(ref); }

  Member<GCed> ref;
};

class GCedWithInlinedArray : public GarbageCollected<GCedWithInlinedArray> {
 public:
  static constexpr size_t kNumReferences = 4;

  explicit GCedWithInlinedArray(GCed* value2) {
    new (&objects[2].ref) Member<GCed>(value2);
  }

  void Trace(cppgc::Visitor* v) const {
    for (size_t i = 0; i < kNumReferences; ++i) {
      v->Trace(objects[i]);
    }
  }

  InlinedObject objects[kNumReferences];
};

}  // namespace

TEST_F(WriteBarrierTest, DijkstraWriteBarrierRangeTriggersWhenMarkingIsOn) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCedWithInlinedArray>(
      GetAllocationHandle(), object1);
  {
    ExpectWriteBarrierFires scope(marker(), {object1});
    EXPECT_FALSE(object1->IsMarked());
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  object2->objects, params, [this]() -> HeapHandle& {
                    return GetHeap()->GetHeapHandle();
                  }));
    HeapConsistency::DijkstraWriteBarrierRange(
        params, object2->objects, sizeof(InlinedObject), 4,
        TraceTrait<InlinedObject>::Trace);
    EXPECT_TRUE(object1->IsMarked());
  }
}

TEST_F(WriteBarrierTest, DijkstraWriteBarrierRangeBailoutIfMarked) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCedWithInlinedArray>(
      GetAllocationHandle(), object1);
  EXPECT_TRUE(HeapObjectHeader::FromObject(object1).TryMarkAtomic());
  {
    ExpectNoWriteBarrierFires scope(marker(), {object1});
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  object2->objects, params, [this]() -> HeapHandle& {
                    return GetHeap()->GetHeapHandle();
                  }));
    HeapConsistency::DijkstraWriteBarrierRange(
        params, object2->objects, sizeof(InlinedObject), 4,
        TraceTrait<InlinedObject>::Trace);
  }
}

TEST_F(WriteBarrierTest, SteeleWriteBarrierTriggersWhenMarkingIsOn) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
  {
    ExpectWriteBarrierFires scope(marker(), {object1});
    EXPECT_TRUE(HeapObjectHeader::FromObject(object1).TryMarkAtomic());
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  &object2->next_ref(), object2->next_ref().Get(), params));
    HeapConsistency::SteeleWriteBarrier(params, object2->next_ref().Get());
  }
}

TEST_F(WriteBarrierTest, SteeleWriteBarrierBailoutIfNotMarked) {
  auto* object1 = MakeGarbageCollected<GCed>(GetAllocationHandle());
  auto* object2 = MakeGarbageCollected<GCed>(GetAllocationHandle(), object1);
  {
    ExpectNoWriteBarrierFires scope(marker(), {object1});
    WriteBarrierParams params;
    EXPECT_EQ(WriteBarrierType::kMarking,
              HeapConsistency::GetWriteBarrierType(
                  &object2->next_ref(), object2->next_ref().Get(), params));
    HeapConsistency::SteeleWriteBarrier(params, object2->next_ref().Get());
  }
}

}  // namespace internal
}  // namespace cppgc