cppgc: Enable concurrent marking/sweeping for unified heap

Bug: chromium:1056170
Change-Id: I010ab2ff2c55ce54b5dcc2df6fb7bbcd14b03e2a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2480568Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70599}

src/heap/cppgc-js/cpp-heap.cc

@@ -169,10 +169,13 @@ void CppHeap::RegisterV8References(
 }
 
 void CppHeap::TracePrologue(TraceFlags flags) {
+  // Finish sweeping in case it is still running.
+  sweeper_.FinishIfRunning();
+
   const UnifiedHeapMarker::MarkingConfig marking_config{
       UnifiedHeapMarker::MarkingConfig::CollectionType::kMajor,
       cppgc::Heap::StackState::kNoHeapPointers,
-      UnifiedHeapMarker::MarkingConfig::MarkingType::kIncremental};
+      UnifiedHeapMarker::MarkingConfig::MarkingType::kIncrementalAndConcurrent};
   marker_ =
       cppgc::internal::MarkerFactory::CreateAndStartMarking<UnifiedHeapMarker>(
           *isolate_.heap(), AsBase(), platform_.get(), marking_config);
@@ -210,7 +213,8 @@ void CppHeap::TraceEpilogue(TraceSummary* trace_summary) {
 #endif
   {
     NoGCScope no_gc(*this);
-    sweeper().Start(cppgc::internal::Sweeper::Config::kAtomic);
+    sweeper().Start(
+        cppgc::internal::Sweeper::Config::kIncrementalAndConcurrent);
   }
 }
 

src/heap/cppgc-js/cpp-snapshot.cc

@@ -580,6 +580,9 @@ void CppGraphBuilderImpl::VisitRootForGraphBuilding(
 }
 
 void CppGraphBuilderImpl::Run() {
+  // Sweeping from a previous GC might still be running, in which case not all
+  // pages have been returned to spaces yet.
+  cpp_heap_.sweeper().FinishIfRunning();
   // First pass: Figure out which objects should be included in the graph -- see
   // class-level comment on CppGraphBuilder.
   LiveObjectsForVisibilityIterator visitor(*this);

test/unittests/heap/unified-heap-unittest.cc

@@ -94,6 +94,8 @@ TEST_F(UnifiedHeapTest, FindingV8ToBlinkReference) {
   EXPECT_EQ(0u, Wrappable::destructor_callcount);
   ResetWrappableConnection(api_object);
   CollectGarbage(OLD_SPACE);
+  // Calling CollectGarbage twice to force the first GC to finish sweeping.
+  CollectGarbage(OLD_SPACE);
   EXPECT_EQ(1u, Wrappable::destructor_callcount);
 }