[wasm] Use WeakFixedArray for list of instances sharing a WasmMemoryObject.

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/debug/debug.h"
 #include "src/debug/interface-types.h"
 #include "src/objects.h"
@@ skipping 11 matching lines @@
 namespace v8 {
 namespace internal {
 namespace wasm {
 class InterpretedFrame;
 class WasmInterpreter;
 }
 
 class WasmCompiledModule;
 class WasmDebugInfo;
 class WasmInstanceObject;
-class WasmInstanceWrapper;
 
 #define DECL_OOL_QUERY(type) static bool Is##type(Object* object);
 #define DECL_OOL_CAST(type) static type* cast(Object* object);
 
 #define DECL_GETTER(name, type) type* name();
 
 #define DECL_OPTIONAL_ACCESSORS(name, type) \
   INLINE(bool has_##name());                \
   DECL_ACCESSORS(name, type)
 
@@ skipping 63 matching lines @@
       Handle<FixedArray> function_table, Handle<FixedArray> signature_table);
 };
 
 // Representation of a WebAssembly.Memory JavaScript-level object.
 class WasmMemoryObject : public JSObject {
  public:
   DECL_CAST(WasmMemoryObject)
 
   DECL_ACCESSORS(array_buffer, JSArrayBuffer)
   DECL_INT_ACCESSORS(maximum_pages)
-  DECL_OPTIONAL_ACCESSORS(instances_link, WasmInstanceWrapper)
+  DECL_OPTIONAL_ACCESSORS(instances, WeakFixedArray)
 
   enum {  // --
     kArrayBufferIndex,
     kMaximumPagesIndex,
-    kInstancesLinkIndex,
+    kInstancesIndex,
     kFieldCount
   };
 
   DEF_SIZE(JSObject)
   DEF_OFFSET(ArrayBuffer)
   DEF_OFFSET(MaximumPages)
-  DEF_OFFSET(InstancesLink)
+  DEF_OFFSET(Instances)
 
-  void AddInstance(Isolate* isolate, Handle<WasmInstanceObject> object);
-  inline void ResetInstancesLink(Isolate* isolate);
+  // Add an instance to the internal (weak) list. amortized O(n).
+  static void AddInstance(Isolate* isolate, Handle<WasmMemoryObject> memory,
+                          Handle<WasmInstanceObject> object);
+  // Remove an instance from the internal (weak) list. O(n).
+  static void RemoveInstance(Isolate* isolate, Handle<WasmMemoryObject> memory,
+                             Handle<WasmInstanceObject> object);
   uint32_t current_pages();
   inline bool has_maximum_pages() { return maximum_pages() >= 0; }
 
   static Handle<WasmMemoryObject> New(Isolate* isolate,
                                       Handle<JSArrayBuffer> buffer,
                                       int32_t maximum);
 
   static int32_t Grow(Isolate*, Handle<WasmMemoryObject>, uint32_t pages);
 };
 
 // A WebAssembly.Instance JavaScript-level object.
 class WasmInstanceObject : public JSObject {
  public:
   DECL_CAST(WasmInstanceObject)
 
   DECL_ACCESSORS(compiled_module, WasmCompiledModule)
   DECL_OPTIONAL_ACCESSORS(memory_object, WasmMemoryObject)
   DECL_OPTIONAL_ACCESSORS(memory_buffer, JSArrayBuffer)
   DECL_OPTIONAL_ACCESSORS(globals_buffer, JSArrayBuffer)
   DECL_OPTIONAL_ACCESSORS(debug_info, WasmDebugInfo)
-  DECL_OPTIONAL_ACCESSORS(instance_wrapper, WasmInstanceWrapper)
   // FixedArray of all instances whose code was imported
   DECL_OPTIONAL_ACCESSORS(directly_called_instances, FixedArray)
 
   enum {  // --
     kCompiledModuleIndex,
     kMemoryObjectIndex,
     kMemoryBufferIndex,
     kGlobalsBufferIndex,
     kDebugInfoIndex,
-    kInstanceWrapperIndex,
     kDirectlyCalledInstancesIndex,
     kFieldCount
   };
 
   DEF_SIZE(JSObject)
   DEF_OFFSET(CompiledModule)
   DEF_OFFSET(MemoryObject)
   DEF_OFFSET(MemoryBuffer)
   DEF_OFFSET(GlobalsBuffer)
   DEF_OFFSET(DebugInfo)
-  DEF_OFFSET(InstanceWrapper)
   DEF_OFFSET(DirectlyCalledInstances)
 
   WasmModuleObject* module_object();
   V8_EXPORT_PRIVATE wasm::WasmModule* module();
 
   // Get the debug info associated with the given wasm object.
   // If no debug info exists yet, it is created automatically.
   static Handle<WasmDebugInfo> GetOrCreateDebugInfo(Handle<WasmInstanceObject>);
 
   static Handle<WasmInstanceObject> New(Isolate*, Handle<WasmCompiledModule>);
@@ skipping 477 matching lines @@
   // for the local scope. Both elements are JSArrays of size
   // ScopeIterator::kScopeDetailsSize and layout as described in debug-scopes.h.
   // The global scope contains information about globals and the memory.
   // The local scope contains information about parameters, locals, and stack
   // values.
   static Handle<JSArray> GetScopeDetails(Handle<WasmDebugInfo>,
                                          Address frame_pointer,
                                          int frame_index);
 };
 
-class WasmInstanceWrapper : public FixedArray {
- public:
-  enum {  // --
-    kWrapperInstanceObjectIndex,
-    kNextInstanceWrapperIndex,
-    kPreviousInstanceWrapperIndex,
-    kFieldCount
-  };
-
-  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(kWrapperInstanceObjectIndex)->IsWeakCell(); }
-  Handle<WasmInstanceObject> instance_object() {
-    Object* obj = get(kWrapperInstanceObjectIndex);
-    DCHECK(obj->IsWeakCell());
-    WeakCell* cell = WeakCell::cast(obj);
-    DCHECK(cell->value()->IsJSObject());
-    return handle(WasmInstanceObject::cast(cell->value()));
-  }
-  bool has_next() {
-    return IsWasmInstanceWrapper(get(kNextInstanceWrapperIndex));
-  }
-  bool has_previous() {
-    return IsWasmInstanceWrapper(get(kPreviousInstanceWrapperIndex));
-  }
-  void set_next_wrapper(Object* obj) {
-    DCHECK(IsWasmInstanceWrapper(obj));
-    set(kNextInstanceWrapperIndex, obj);
-  }
-  void set_previous_wrapper(Object* obj) {
-    DCHECK(IsWasmInstanceWrapper(obj));
-    set(kPreviousInstanceWrapperIndex, obj);
-  }
-  Handle<WasmInstanceWrapper> next_wrapper() {
-    Object* obj = get(kNextInstanceWrapperIndex);
-    DCHECK(IsWasmInstanceWrapper(obj));
-    return handle(WasmInstanceWrapper::cast(obj));
-  }
-  Handle<WasmInstanceWrapper> previous_wrapper() {
-    Object* obj = get(kPreviousInstanceWrapperIndex);
-    DCHECK(IsWasmInstanceWrapper(obj));
-    return handle(WasmInstanceWrapper::cast(obj));
-  }
-  void reset_next_wrapper() { set_undefined(kNextInstanceWrapperIndex); }
-  void reset_previous_wrapper() {
-    set_undefined(kPreviousInstanceWrapperIndex);
-  }
-  void reset() {
-    for (int kID = 0; kID < kFieldCount; kID++) set_undefined(kID);
-  }
-
-  static Handle<WasmInstanceWrapper> New(Isolate* isolate,
-                                         Handle<WasmInstanceObject> instance);
-};
-
 // TODO(titzer): these should be moved to wasm-objects-inl.h
 CAST_ACCESSOR(WasmInstanceObject)
 CAST_ACCESSOR(WasmMemoryObject)
 CAST_ACCESSOR(WasmModuleObject)
 CAST_ACCESSOR(WasmTableObject)
 
 // WasmModuleObject
 ACCESSORS(WasmModuleObject, compiled_module, WasmCompiledModule,
           kCompiledModuleOffset)
 
 // WasmTableObject
 ACCESSORS(WasmTableObject, functions, FixedArray, kFunctionsOffset)
 SMI_ACCESSORS(WasmTableObject, maximum_length, kMaximumLengthOffset)
 ACCESSORS(WasmTableObject, dispatch_tables, FixedArray, kDispatchTablesOffset)
 
 // WasmMemoryObject
 ACCESSORS(WasmMemoryObject, array_buffer, JSArrayBuffer, kArrayBufferOffset)
 SMI_ACCESSORS(WasmMemoryObject, maximum_pages, kMaximumPagesOffset)
-ACCESSORS(WasmMemoryObject, instances_link, WasmInstanceWrapper,
-          kInstancesLinkOffset)
+ACCESSORS(WasmMemoryObject, instances, WeakFixedArray, kInstancesOffset)
 
 // WasmInstanceObject
 ACCESSORS(WasmInstanceObject, compiled_module, WasmCompiledModule,
           kCompiledModuleOffset)
 ACCESSORS(WasmInstanceObject, memory_object, WasmMemoryObject,
           kMemoryObjectOffset)
 ACCESSORS(WasmInstanceObject, memory_buffer, JSArrayBuffer, kMemoryBufferOffset)
 ACCESSORS(WasmInstanceObject, globals_buffer, JSArrayBuffer,
           kGlobalsBufferOffset)
 ACCESSORS(WasmInstanceObject, debug_info, WasmDebugInfo, kDebugInfoOffset)
-ACCESSORS(WasmInstanceObject, instance_wrapper, WasmInstanceWrapper,
-          kInstanceWrapperOffset)
 ACCESSORS(WasmInstanceObject, directly_called_instances, FixedArray,
           kDirectlyCalledInstancesOffset)
 
 // WasmExportedFunction
 ACCESSORS(WasmExportedFunction, instance, WasmInstanceObject, kInstanceOffset)
 SMI_ACCESSORS(WasmExportedFunction, function_index, kFunctionIndexOffset)
 
 // WasmSharedModuleData
 ACCESSORS(WasmSharedModuleData, module_bytes, SeqOneByteString,
           kModuleBytesOffset)
 ACCESSORS(WasmSharedModuleData, script, Script, kScriptOffset)
 ACCESSORS(WasmSharedModuleData, asm_js_offset_table, ByteArray,
           kAsmJsOffsetTableOffset)
 ACCESSORS(WasmSharedModuleData, breakpoint_infos, FixedArray,
           kBreakPointInfosOffset)
 
 #define OPTIONAL_ACCESSOR(holder, name, offset)                  \
   bool holder::has_##name() {                                    \
     return !READ_FIELD(this, offset)->IsUndefined(GetIsolate()); \
   }
 
 OPTIONAL_ACCESSOR(WasmInstanceObject, debug_info, kDebugInfoOffset)
 OPTIONAL_ACCESSOR(WasmInstanceObject, memory_buffer, kMemoryBufferOffset)
 OPTIONAL_ACCESSOR(WasmInstanceObject, memory_object, kMemoryObjectOffset)
-OPTIONAL_ACCESSOR(WasmInstanceObject, instance_wrapper, kInstanceWrapperOffset)
 
-OPTIONAL_ACCESSOR(WasmMemoryObject, instances_link, kInstancesLinkOffset)
+OPTIONAL_ACCESSOR(WasmMemoryObject, instances, kInstancesOffset)
 
 OPTIONAL_ACCESSOR(WasmSharedModuleData, breakpoint_infos,
                   kBreakPointInfosOffset)
 OPTIONAL_ACCESSOR(WasmSharedModuleData, asm_js_offset_table,
                   kAsmJsOffsetTableOffset)
 OPTIONAL_ACCESSOR(WasmSharedModuleData, lazy_compilation_orchestrator,
                   kLazyCompilationOrchestratorOffset)
 
 ACCESSORS(WasmDebugInfo, locals_names, FixedArray, kLocalsNamesOffset)
 
 OPTIONAL_ACCESSOR(WasmDebugInfo, locals_names, kLocalsNamesOffset)
 
-inline void WasmMemoryObject::ResetInstancesLink(Isolate* isolate) {
-  // This has to be a raw access to bypass typechecking.
-  WRITE_FIELD(this, kInstancesLinkOffset, isolate->heap()->undefined_value());
-}
-
 #undef DECL_OOL_QUERY
 #undef DECL_OOL_CAST
 #undef DECL_GETTER
 #undef DECL_OPTIONAL_ACCESSORS
 #undef DECL_OPTIONAL_GETTER
 
 #include "src/objects/object-macros-undef.h"
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_OBJECTS_H_