[heap] Simplify visitation of weak next code link field.

R=ulan@chromium.org

Change-Id: I141daeffde426a75293ffa0565c867d73a81cbfc
Reviewed-on: https://chromium-review.googlesource.com/738776Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48968}

src/heap/mark-compact-inl.h

@@ -43,6 +43,15 @@ int MarkingVisitor<fixed_array_mode, retaining_path_mode,
   return size;
 }
 
+template <FixedArrayVisitationMode fixed_array_mode,
+          TraceRetainingPathMode retaining_path_mode, typename MarkingState>
+int MarkingVisitor<fixed_array_mode, retaining_path_mode, MarkingState>::
+    VisitCodeDataContainer(Map* map, CodeDataContainer* object) {
+  int size = CodeDataContainer::BodyDescriptorWeak::SizeOf(map, object);
+  CodeDataContainer::BodyDescriptorWeak::IterateBody(object, size, this);
+  return size;
+}
+
 template <FixedArrayVisitationMode fixed_array_mode,
           TraceRetainingPathMode retaining_path_mode, typename MarkingState>
 int MarkingVisitor<fixed_array_mode, retaining_path_mode,

src/heap/mark-compact.cc

@@ -1187,9 +1187,6 @@ class MarkCompactCollector::CustomRootBodyMarkingVisitor final
 
   // VisitEmbedderPointer is defined by ObjectVisitor to call VisitPointers.
 
-  // Skip the weak next code link for code objects.
-  void VisitNextCodeLink(CodeDataContainer* host, Object** p) override {}
-
  private:
   void MarkObject(HeapObject* host, Object* object) {
     if (!object->IsHeapObject()) return;

src/heap/mark-compact.h

@@ -1034,6 +1034,7 @@ class MarkingVisitor final
 
   V8_INLINE int VisitAllocationSite(Map* map, AllocationSite* object);
   V8_INLINE int VisitBytecodeArray(Map* map, BytecodeArray* object);
+  V8_INLINE int VisitCodeDataContainer(Map* map, CodeDataContainer* object);
   V8_INLINE int VisitFixedArray(Map* map, FixedArray* object);
   V8_INLINE int VisitJSApiObject(Map* map, JSObject* object);
   V8_INLINE int VisitJSFunction(Map* map, JSFunction* object);
@@ -1049,8 +1050,6 @@ class MarkingVisitor final
                                Object** end) final;
   V8_INLINE void VisitEmbeddedPointer(Code* host, RelocInfo* rinfo) final;
   V8_INLINE void VisitCodeTarget(Code* host, RelocInfo* rinfo) final;
-  // Skip weak next code link.
-  V8_INLINE void VisitNextCodeLink(CodeDataContainer* host, Object** p) final {}
 
  private:
   // Granularity in which FixedArrays are scanned if |fixed_array_mode|

src/objects-body-descriptors-inl.h

@@ -395,25 +395,6 @@ class Code::BodyDescriptor final : public BodyDescriptorBase {
   }
 };
 
-class CodeDataContainer::BodyDescriptor final : public BodyDescriptorBase {
- public:
-  static bool IsValidSlot(HeapObject* obj, int offset) { return true; }
-
-  template <typename ObjectVisitor>
-  static inline void IterateBody(HeapObject* obj, ObjectVisitor* v) {
-    v->VisitNextCodeLink(CodeDataContainer::cast(obj),
-                         HeapObject::RawField(obj, kNextCodeLinkOffset));
-  }
-
-  template <typename ObjectVisitor>
-  static inline void IterateBody(HeapObject* obj, int object_size,
-                                 ObjectVisitor* v) {
-    IterateBody(obj, v);
-  }
-
-  static inline int SizeOf(Map* map, HeapObject* obj) { return kSize; }
-};
-
 class SeqOneByteString::BodyDescriptor final : public BodyDescriptorBase {
  public:
   static bool IsValidSlot(HeapObject* obj, int offset) { return false; }

src/objects/code.h

@@ -532,7 +532,19 @@ class CodeDataContainer : public HeapObject {
   static const int kUnalignedSize = kKindSpecificFlagsOffset + kIntSize;
   static const int kSize = OBJECT_POINTER_ALIGN(kUnalignedSize);
 
-  class BodyDescriptor;
+  // During mark compact we need to take special care for weak fields.
+  static const int kPointerFieldsStrongEndOffset = kNextCodeLinkOffset;
+  static const int kPointerFieldsWeakEndOffset = kKindSpecificFlagsOffset;
+
+  // Ignores weakness.
+  typedef FixedBodyDescriptor<HeapObject::kHeaderSize,
+                              kPointerFieldsWeakEndOffset, kSize>
+      BodyDescriptor;
+
+  // Respects weakness.
+  typedef FixedBodyDescriptor<HeapObject::kHeaderSize,
+                              kPointerFieldsStrongEndOffset, kSize>
+      BodyDescriptorWeak;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(CodeDataContainer);

src/visitors.cc

@@ -20,9 +20,5 @@ const char* const VisitorSynchronization::kTagNames
     [VisitorSynchronization::kNumberOfSyncTags] = {ROOT_ID_LIST(DECLARE_TAG)};
 #undef DECLARE_TAG
 
-void ObjectVisitor::VisitNextCodeLink(CodeDataContainer* host, Object** p) {
-  VisitPointers(host, p, p + 1);
-}
-
 }  // namespace internal
 }  // namespace v8

src/visitors.h

@@ -92,11 +92,8 @@ class ObjectVisitor BASE_EMBEDDED {
     VisitPointers(host, p, p + 1);
   }
 
-  // Visit the weak next code link for code objects.
-  virtual void VisitNextCodeLink(CodeDataContainer* host, Object** p);
-
   // To allow lazy clearing of inline caches the visitor has
-  // a rich interface for iterating over Code objects..
+  // a rich interface for iterating over Code objects ...
 
   // Visits a code target in the instruction stream.
   virtual void VisitCodeTarget(Code* host, RelocInfo* rinfo);