[wasm] WebAssembly.Memory object can be referenced by multiple Instance objects.

src/wasm/wasm-objects.h

 // Copyright 2016 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.
 
 #ifndef V8_WASM_OBJECTS_H_
 #define V8_WASM_OBJECTS_H_
 
 #include "src/objects-inl.h"
 #include "src/wasm/managed.h"
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 struct WasmModule;
 }
 
 class WasmCompiledModule;
 class WasmDebugInfo;
 class WasmInstanceObject;
+class WasmInstanceWrapper;
 
 #define DECLARE_CASTS(name)             \
   static bool Is##name(Object* object); \
   static name* cast(Object* object)
 
 #define DECLARE_ACCESSORS(name, type) \
   type* get_##name();                 \
   void set_##name(type* value)
 
 #define DECLARE_OPTIONAL_ACCESSORS(name, type) \
@@ skipping 42 matching lines @@
   static Handle<FixedArray> AddDispatchTable(
       Isolate* isolate, Handle<WasmTableObject> table,
       Handle<WasmInstanceObject> instance, int table_index,
       Handle<FixedArray> dispatch_table);
 };
 
 // Representation of a WebAssembly.Memory JavaScript-level object.
 class WasmMemoryObject : public JSObject {
  public:
   // TODO(titzer): add the brand as an internal field instead of a property.
-  enum Fields : uint8_t { kArrayBuffer, kMaximum, kInstance, kFieldCount };
+  enum Fields : uint8_t { kArrayBuffer, kMaximum, kInstancesLink, kFieldCount };
 
   DECLARE_CASTS(WasmMemoryObject);
   DECLARE_ACCESSORS(buffer, JSArrayBuffer);
+  DECLARE_OPTIONAL_ACCESSORS(instances_link, WasmInstanceWrapper);
 
-  void AddInstance(WasmInstanceObject* object);
+  void AddInstance(Isolate* isolate, Handle<WasmInstanceObject> object);
+  void ResetInstancesLink(Isolate* isolate);
   uint32_t current_pages();
   int32_t maximum_pages();  // returns < 0 if there is no maximum
 
   static Handle<WasmMemoryObject> New(Isolate* isolate,
                                       Handle<JSArrayBuffer> buffer,
                                       int maximum);
 
   static bool Grow(Handle<WasmMemoryObject> memory, uint32_t count);
 };
 
 // Representation of a WebAssembly.Instance JavaScript-level object.
 class WasmInstanceObject : public JSObject {
  public:
   // TODO(titzer): add the brand as an internal field instead of a property.
   enum Fields {
     kCompiledModule,
     kMemoryObject,
     kMemoryArrayBuffer,
     kGlobalsArrayBuffer,
     kDebugInfo,
+    kWasmMemInstanceWrapper,
     kFieldCount
   };
 
   DECLARE_CASTS(WasmInstanceObject);
 
   DECLARE_ACCESSORS(compiled_module, WasmCompiledModule);
   DECLARE_OPTIONAL_ACCESSORS(globals_buffer, JSArrayBuffer);
   DECLARE_OPTIONAL_ACCESSORS(memory_buffer, JSArrayBuffer);
   DECLARE_OPTIONAL_ACCESSORS(memory_object, WasmMemoryObject);
   DECLARE_OPTIONAL_ACCESSORS(debug_info, WasmDebugInfo);
+  DECLARE_OPTIONAL_ACCESSORS(instance_wrapper, WasmInstanceWrapper);
 
   WasmModuleObject* module_object();
   wasm::WasmModule* module();
 
   static Handle<WasmInstanceObject> New(
       Isolate* isolate, Handle<WasmCompiledModule> compiled_module);
 };
 
 // Representation of an exported WASM function.
 class WasmExportedFunction : public JSFunction {
@@ skipping 191 matching lines @@
   // column.
   static Handle<FixedArray> GetFunctionOffsetTable(
       Handle<WasmDebugInfo> debug_info, int func_index);
 
   // Get the asm.js source position from a byte offset.
   // Must only be called if the associated wasm object was created from asm.js.
   static int GetAsmJsSourcePosition(Handle<WasmDebugInfo> debug_info,
                                     int func_index, int byte_offset);
 };
 
+class WasmInstanceWrapper : public FixedArray {
+ public:
+  static Handle<WasmInstanceWrapper> New(Isolate* isolate,
+                                         Handle<WasmInstanceObject> instance);
+  static WasmInstanceWrapper* cast(Object* fixed_array) {
+    SLOW_DCHECK(IsWasmInstanceWrapper(fixed_array));
+    return reinterpret_cast<WasmInstanceWrapper*>(fixed_array);
+  }
+  static bool IsWasmInstanceWrapper(Object* obj);
+  bool has_instance() { return get(kWrapperInstanceObject)->IsWeakCell(); }
+  Handle<WasmInstanceObject> instance_object() {
+    Object* obj = get(kWrapperInstanceObject);
+    DCHECK(obj->IsWeakCell());
+    WeakCell* cell = WeakCell::cast(obj);
+    DCHECK(cell->value()->IsJSObject());
+    return handle(WasmInstanceObject::cast(cell->value()));
+  }
+  bool has_next() { return IsWasmInstanceWrapper(get(kNextInstanceWrapper)); }
+  bool has_previous() {
+    return IsWasmInstanceWrapper(get(kPreviousInstanceWrapper));
+  }
+  void set_instance_object(Handle<JSObject> instance, Isolate* isolate);
+  void set_next_wrapper(Object* obj) {
+    DCHECK(IsWasmInstanceWrapper(obj));
+    set(kNextInstanceWrapper, obj);
+  }
+  void set_previous_wrapper(Object* obj) {
+    DCHECK(IsWasmInstanceWrapper(obj));
+    set(kPreviousInstanceWrapper, obj);
+  }
+  Handle<WasmInstanceWrapper> next_wrapper() {
+    Object* obj = get(kNextInstanceWrapper);
+    DCHECK(IsWasmInstanceWrapper(obj));
+    return handle(WasmInstanceWrapper::cast(obj));
+  }
+  Handle<WasmInstanceWrapper> previous_wrapper() {
+    Object* obj = get(kPreviousInstanceWrapper);
+    DCHECK(IsWasmInstanceWrapper(obj));
+    return handle(WasmInstanceWrapper::cast(obj));
+  }
+  void reset_next_wrapper() { set_undefined(kNextInstanceWrapper); }
+  void reset_previous_wrapper() { set_undefined(kPreviousInstanceWrapper); }
+  void reset() {
+    for (int kID = 0; kID < kWrapperPropertyCount; kID++) set_undefined(kID);
+  }
+
+ private:
+  enum {
+    kWrapperInstanceObject,
+    kNextInstanceWrapper,
+    kPreviousInstanceWrapper,
+    kWrapperPropertyCount
+  };
+};
+
 #undef DECLARE_ACCESSORS
 #undef DECLARE_OPTIONAL_ACCESSORS
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_OBJECTS_H_