[GetIsolate] Add a mixin for safe GetIsolate types

To avoid repeating code for the few places where we can call GetIsolate
and GetHeap safely.

Bug: v8:7786
Change-Id: I6c6de81488bfa79dca50cfd2b6356f432401b68e
Reviewed-on: https://chromium-review.googlesource.com/1104684
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53828}

src/contexts-inl.h

@@ -45,8 +45,6 @@ Context* Context::cast(Object* context) {
   return reinterpret_cast<Context*>(context);
 }
 
-Isolate* Context::GetIsolate() const { return GetHeap()->isolate(); }
-
 void Context::set_scope_info(ScopeInfo* scope_info) {
   set(SCOPE_INFO_INDEX, scope_info);
 }

src/contexts.h

@@ -434,13 +434,16 @@ class ScriptContextTable : public FixedArray {
 // Script contexts from all top-level scripts are gathered in
 // ScriptContextTable.
 
-class Context : public FixedArray {
+class Context : public FixedArray, public NeverReadOnlySpaceObject {
  public:
+  // Use the mixin methods over the HeapObject methods.
+  // TODO(v8:7786) Remove once the HeapObject methods are gone.
+  using NeverReadOnlySpaceObject::GetHeap;
+  using NeverReadOnlySpaceObject::GetIsolate;
+
   // Conversions.
   static inline Context* cast(Object* context);
 
-  inline Isolate* GetIsolate() const;
-
   // The default context slot layout; indices are FixedArray slot indices.
   enum Field {
     // These slots are in all contexts.

src/objects-inl.h

@@ -1016,7 +1016,19 @@ Isolate* HeapObject::GetIsolate() const {
   return GetHeap()->isolate();
 }
 
-Isolate* JSReceiver::GetIsolate() const { return GetHeap()->isolate(); }
+Heap* NeverReadOnlySpaceObject::GetHeap() const {
+  MemoryChunk* chunk =
+      MemoryChunk::FromAddress(reinterpret_cast<Address>(this));
+  // Make sure we are not accessing an object in RO space.
+  SLOW_DCHECK(chunk->owner()->identity() != RO_SPACE);
+  Heap* heap = chunk->heap();
+  SLOW_DCHECK(heap != nullptr);
+  return heap;
+}
+
+Isolate* NeverReadOnlySpaceObject::GetIsolate() const {
+  return GetHeap()->isolate();
+}
 
 Map* HeapObject::map() const {
   return map_word().ToMap();

src/objects.h

@@ -1809,14 +1809,14 @@ class HeapObject: public Object {
 
   // The Heap the object was allocated in. Used also to access Isolate.
 #ifdef DEPRECATE_GET_ISOLATE
-  [[deprecated("Pass Heap explicitly")]]
+  [[deprecated("Pass Heap explicitly or use a NeverReadOnlyHeapObject")]]
 #endif
       inline Heap*
       GetHeap() const;
 
 // Convenience method to get current isolate.
 #ifdef DEPRECATE_GET_ISOLATE
-  [[deprecated("Pass Isolate explicitly")]]
+  [[deprecated("Pass Isolate explicitly or use a NeverReadOnlyHeapObject")]]
 #endif
       inline Isolate*
       GetIsolate() const;
@@ -1953,6 +1953,17 @@ class HeapObject: public Object {
   DISALLOW_IMPLICIT_CONSTRUCTORS(HeapObject);
 };
 
+// Mixin class for objects that can never be in RO space.
+// TODO(leszeks): Add checks in the factory that we never allocate these objects
+// in RO space.
+class NeverReadOnlySpaceObject {
+ public:
+  // The Heap the object was allocated in. Used also to access Isolate.
+  inline Heap* GetHeap() const;
+
+  // Convenience method to get current isolate.
+  inline Isolate* GetIsolate() const;
+};
 
 template <int start_offset, int end_offset, int size>
 class FixedBodyDescriptor;
@@ -2096,13 +2107,16 @@ class PropertyArray : public HeapObject {
 
 // JSReceiver includes types on which properties can be defined, i.e.,
 // JSObject and JSProxy.
-class JSReceiver: public HeapObject {
+class JSReceiver : public HeapObject, public NeverReadOnlySpaceObject {
  public:
+  // Use the mixin methods over the HeapObject methods.
+  // TODO(v8:7786) Remove once the HeapObject methods are gone.
+  using NeverReadOnlySpaceObject::GetHeap;
+  using NeverReadOnlySpaceObject::GetIsolate;
+
   // Returns true if there is no slow (ie, dictionary) backing store.
   inline bool HasFastProperties() const;
 
-  inline Isolate* GetIsolate() const;
-
   // Returns the properties array backing store if it
   // exists. Otherwise, returns an empty_property_array when there's a
   // Smi (hash code) or an empty_fixed_array for a fast properties