[heap] More accurate native context inference

This adds inference for general JSObjects to NativeContextInferrer in
the case when the object is going to be attributed to the shard context.

Bug: chromium:973627
Change-Id: I393e8dd16a1f8b615fb2f8dceb52f543bae33554
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1997133Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65736}

src/heap/concurrent-marking.cc

@@ -399,9 +399,10 @@ void ConcurrentMarking::Run(int task_id, TaskState* task_state) {
   NativeContextStats& native_context_stats = task_state->native_context_stats;
   double time_ms;
   size_t marked_bytes = 0;
+  Isolate* isolate = heap_->isolate();
   if (FLAG_trace_concurrent_marking) {
-    heap_->isolate()->PrintWithTimestamp(
-        "Starting concurrent marking task %d\n", task_id);
+    isolate->PrintWithTimestamp("Starting concurrent marking task %d\n",
+                                task_id);
   }
   bool ephemeron_marked = false;
 
@@ -439,10 +440,10 @@ void ConcurrentMarking::Run(int task_id, TaskState* task_state) {
             addr == new_large_object) {
           marking_worklists.PushOnHold(object);
         } else {
-          Map map = object.synchronized_map();
+          Map map = object.synchronized_map(isolate);
           if (is_per_context_mode) {
             Address context;
-            if (native_context_inferrer.Infer(map, object, &context)) {
+            if (native_context_inferrer.Infer(isolate, map, object, &context)) {
               marking_worklists.SwitchToContext(context);
             }
           }

src/heap/mark-compact.cc

@@ -1803,6 +1803,7 @@ size_t MarkCompactCollector::ProcessMarkingWorklist(size_t bytes_to_process) {
   HeapObject object;
   size_t bytes_processed = 0;
   bool is_per_context_mode = marking_worklists()->IsPerContextMode();
+  Isolate* isolate = heap()->isolate();
   while (marking_worklists()->Pop(&object) ||
          marking_worklists()->PopOnHold(&object)) {
     // Left trimming may result in grey or black filler objects on the marking
@@ -1827,10 +1828,10 @@ size_t MarkCompactCollector::ProcessMarkingWorklist(size_t bytes_to_process) {
                     kTrackNewlyDiscoveredObjects) {
       AddNewlyDiscovered(object);
     }
-    Map map = object.map();
+    Map map = object.map(isolate);
     if (is_per_context_mode) {
       Address context;
-      if (native_context_inferrer_.Infer(map, object, &context)) {
+      if (native_context_inferrer_.Infer(isolate, map, object, &context)) {
         marking_worklists()->SwitchToContext(context);
       }
     }

src/heap/marking-worklist.h

@@ -124,6 +124,8 @@ class V8_EXPORT_PRIVATE MarkingWorklistsHolder {
 // A thread-local view of the marking worklists.
 class V8_EXPORT_PRIVATE MarkingWorklists {
  public:
+  static const Address kSharedContext = 0;
+
   MarkingWorklists(int task_id, MarkingWorklistsHolder* holder);
 
   void Push(HeapObject object) {
@@ -179,7 +181,6 @@ class V8_EXPORT_PRIVATE MarkingWorklists {
   bool IsPerContextMode() { return is_per_context_mode_; }
 
  private:
-  const Address kSharedContext = 0;
   bool PopContext(HeapObject* object);
   Address SwitchToContextSlow(Address context);
   MarkingWorklist* shared_;

src/heap/memory-measurement-inl.h

@@ -14,7 +14,7 @@
 namespace v8 {
 namespace internal {
 
-bool NativeContextInferrer::Infer(Map map, HeapObject object,
+bool NativeContextInferrer::Infer(Isolate* isolate, Map map, HeapObject object,
                                   Address* native_context) {
   switch (map.visitor_id()) {
     case kVisitContext:
@@ -24,14 +24,15 @@ bool NativeContextInferrer::Infer(Map map, HeapObject object,
       *native_context = object.ptr();
       return true;
     case kVisitJSFunction:
-      return InferForJSFunction(map, JSFunction::cast(object), native_context);
+      return InferForJSFunction(JSFunction::cast(object), native_context);
     case kVisitJSApiObject:
     case kVisitJSArrayBuffer:
     case kVisitJSObject:
     case kVisitJSObjectFast:
     case kVisitJSTypedArray:
     case kVisitJSWeakCollection:
-      return InferForJSObject(map, JSObject::cast(object), native_context);
+      return InferForJSObject(isolate, map, JSObject::cast(object),
+                              native_context);
     default:
       return false;
   }

src/heap/memory-measurement.cc

@@ -8,6 +8,7 @@
 #include "src/execution/isolate.h"
 #include "src/heap/factory-inl.h"
 #include "src/heap/factory.h"
+#include "src/heap/marking-worklist.h"
 #include "src/objects/js-promise.h"
 
 namespace v8 {
@@ -76,7 +77,7 @@ Handle<JSPromise> MemoryMeasurement::EnqueueRequest(
   return promise;
 }
 
-bool NativeContextInferrer::InferForJSFunction(Map map, JSFunction function,
+bool NativeContextInferrer::InferForJSFunction(JSFunction function,
                                                Address* native_context) {
   if (function.has_context()) {
     *native_context = function.context().native_context().ptr();
@@ -85,16 +86,28 @@ bool NativeContextInferrer::InferForJSFunction(Map map, JSFunction function,
   return false;
 }
 
-bool NativeContextInferrer::InferForJSObject(Map map, JSObject object,
+bool NativeContextInferrer::InferForJSObject(Isolate* isolate, Map map,
+                                             JSObject object,
                                              Address* native_context) {
   if (map.instance_type() == JS_GLOBAL_OBJECT_TYPE) {
     Object maybe_context =
-        JSGlobalObject::cast(object).native_context_unchecked();
+        JSGlobalObject::cast(object).native_context_unchecked(isolate);
     if (maybe_context.IsNativeContext()) {
       *native_context = maybe_context.ptr();
       return true;
     }
   }
+  if (*native_context == MarkingWorklists::kSharedContext) {
+    // This lookup is expensive, so perform it only if the object is currently
+    // attributed to the shared context.
+    // The maximum number of steps to perform when looking for the context.
+    const int kMaxSteps = 3;
+    Object maybe_constructor = map.TryGetConstructor(isolate, kMaxSteps);
+    if (maybe_constructor.IsJSFunction()) {
+      return InferForJSFunction(JSFunction::cast(maybe_constructor),
+                                native_context);
+    }
+  }
   return false;
 }
 

src/heap/memory-measurement.h

@@ -29,12 +29,17 @@ class V8_EXPORT_PRIVATE MemoryMeasurement {
 // Infers the native context for some of the heap objects.
 class V8_EXPORT_PRIVATE NativeContextInferrer {
  public:
-  V8_INLINE bool Infer(Map map, HeapObject object, Address* native_context);
+  // The native_context parameter is both the input and output parameter.
+  // It should be initialized to the context that will be used for the object
+  // if the inference is not successful. The function performs more work if the
+  // context is the shared context.
+  V8_INLINE bool Infer(Isolate* isolate, Map map, HeapObject object,
+                       Address* native_context);
 
  private:
-  bool InferForJSFunction(Map map, JSFunction function,
+  bool InferForJSFunction(JSFunction function, Address* native_context);
+  bool InferForJSObject(Isolate* isolate, Map map, JSObject object,
                         Address* native_context);
-  bool InferForJSObject(Map map, JSObject object, Address* native_context);
 };
 
 // Maintains mapping from native contexts to their sizes.

src/objects/map-inl.h

@@ -765,6 +765,17 @@ DEF_GETTER(Map, GetConstructor, Object) {
   return maybe_constructor;
 }
 
+Object Map::TryGetConstructor(Isolate* isolate, int max_steps) {
+  Object maybe_constructor = constructor_or_backpointer(isolate);
+  // Follow any back pointers.
+  while (maybe_constructor.IsMap(isolate)) {
+    if (max_steps-- == 0) return Smi::FromInt(0);
+    maybe_constructor =
+        Map::cast(maybe_constructor).constructor_or_backpointer(isolate);
+  }
+  return maybe_constructor;
+}
+
 DEF_GETTER(Map, GetFunctionTemplateInfo, FunctionTemplateInfo) {
   Object constructor = GetConstructor(isolate);
   if (constructor.IsJSFunction(isolate)) {

src/objects/map.h

@@ -564,6 +564,10 @@ class Map : public HeapObject {
   DECL_GETTER(GetFunctionTemplateInfo, FunctionTemplateInfo)
   inline void SetConstructor(Object constructor,
                              WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
+  // Constructor getter that performs at most the given number of steps
+  // in the transition tree. Returns either the constructor or the map at
+  // which the walk has stopped.
+  inline Object TryGetConstructor(Isolate* isolate, int max_steps);
   // [back pointer]: points back to the parent map from which a transition
   // leads to this map. The field overlaps with the constructor (see above).
   DECL_GETTER(GetBackPointer, HeapObject)

test/cctest/heap/test-memory-measurement.cc

@@ -28,8 +28,8 @@ TEST(NativeContextInferrerGlobalObject) {
   Handle<JSGlobalObject> global =
       handle(native_context->global_object(), isolate);
   NativeContextInferrer inferrer;
-  Address inferred_context;
-  CHECK(inferrer.Infer(global->map(), *global, &inferred_context));
+  Address inferred_context = 0;
+  CHECK(inferrer.Infer(isolate, global->map(), *global, &inferred_context));
   CHECK_EQ(native_context->ptr(), inferred_context);
 }
 
@@ -42,8 +42,22 @@ TEST(NativeContextInferrerJSFunction) {
   Handle<Object> object = Utils::OpenHandle(*result);
   Handle<HeapObject> function = Handle<HeapObject>::cast(object);
   NativeContextInferrer inferrer;
-  Address inferred_context;
-  CHECK(inferrer.Infer(function->map(), *function, &inferred_context));
+  Address inferred_context = 0;
+  CHECK(inferrer.Infer(isolate, function->map(), *function, &inferred_context));
+  CHECK_EQ(native_context->ptr(), inferred_context);
+}
+
+TEST(NativeContextInferrerJSObject) {
+  LocalContext env;
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+  Handle<NativeContext> native_context = GetNativeContext(isolate, env.local());
+  v8::Local<v8::Value> result = CompileRun("({a : 10})");
+  Handle<Object> object = Utils::OpenHandle(*result);
+  Handle<HeapObject> function = Handle<HeapObject>::cast(object);
+  NativeContextInferrer inferrer;
+  Address inferred_context = 0;
+  CHECK(inferrer.Infer(isolate, function->map(), *function, &inferred_context));
   CHECK_EQ(native_context->ptr(), inferred_context);
 }