[modules] Don't unnecessarily keep function alive after evaluation.

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 7949 matching lines @@
 };
 
 // A Module object is a mapping from export names to cells
 // This is still very much in flux.
 class Module : public Struct {
  public:
   DECLARE_CAST(Module)
   DECLARE_VERIFIER(Module)
   DECLARE_PRINTER(Module)
 
-  // The code representing this Module, either a SharedFunctionInfo or a
-  // JSFunction depending on whether it's been instantiated.
+  // The code representing this Module, or an abstraction thereof.
+  // This is either a SharedFunctionInfo or a JSFunction or a ModuleInfo
+  // depending on whether the module has been instantiated and evaluated.  See
+  // Module::ModuleVerify() for the precise invariant.
   DECL_ACCESSORS(code, Object)
 
+  // The export table.
   DECL_ACCESSORS(exports, ObjectHashTable)
 
   // The namespace object (or undefined).
   DECL_ACCESSORS(module_namespace, HeapObject)
 
   // [[RequestedModules]]: Modules imported or re-exported by this module.
   // Corresponds 1-to-1 to the module specifier strings in
   // ModuleInfo::module_requests.
   DECL_ACCESSORS(requested_modules, FixedArray)
 
-  // [[Evaluated]]: Whether this module has been evaluated. Modules
-  // are only evaluated a single time.
-  DECL_BOOLEAN_ACCESSORS(evaluated)
-
-  // Storage for [[Evaluated]].
-  DECL_INT_ACCESSORS(flags)
-
   // Hash for this object (a random non-zero Smi).
   DECL_INT_ACCESSORS(hash)
 
-  // Get the SharedFunctionInfo associated with the code.
-  inline SharedFunctionInfo* shared() const;
-
   // Get the ModuleInfo associated with the code.
   inline ModuleInfo* info() const;
 
+  inline bool instantiated() const;
+  inline bool evaluated() const;
+  inline void set_evaluated();
+
   // Implementation of spec operation ModuleDeclarationInstantiation.
   // Returns false if an exception occurred during instantiation, true
   // otherwise.
   static MUST_USE_RESULT bool Instantiate(Handle<Module> module,
                                           v8::Local<v8::Context> context,
                                           v8::Module::ResolveCallback callback);
 
   // Implementation of spec operation ModuleEvaluation.
   static MUST_USE_RESULT MaybeHandle<Object> Evaluate(Handle<Module> module);
 
   static Handle<Object> LoadExport(Handle<Module> module, Handle<String> name);
   static void StoreExport(Handle<Module> module, Handle<String> name,
                           Handle<Object> value);
 
   static Handle<Object> LoadImport(Handle<Module> module, Handle<String> name,
                                    int module_request);
 
   // Get the namespace object for [module_request] of [module].  If it doesn't
   // exist yet, it is created.
   static Handle<JSModuleNamespace> GetModuleNamespace(Handle<Module> module,
                                                       int module_request);
 
   static const int kCodeOffset = HeapObject::kHeaderSize;
   static const int kExportsOffset = kCodeOffset + kPointerSize;
   static const int kRequestedModulesOffset = kExportsOffset + kPointerSize;
-  static const int kFlagsOffset = kRequestedModulesOffset + kPointerSize;
-  static const int kEmbedderDataOffset = kFlagsOffset + kPointerSize;
+  static const int kEmbedderDataOffset = kRequestedModulesOffset + kPointerSize;

[adamk, 2016/10/14 18:01:02]

Looks like you'll need a merge here, as embedder data is no more.

   static const int kModuleNamespaceOffset = kEmbedderDataOffset + kPointerSize;
   static const int kHashOffset = kModuleNamespaceOffset + kPointerSize;
   static const int kSize = kHashOffset + kPointerSize;
 
  private:
   enum { kEvaluatedBit };
 
   static void CreateExport(Handle<Module> module, Handle<FixedArray> names);
   static void CreateIndirectExport(Handle<Module> module, Handle<String> name,
                                    Handle<ModuleInfoEntry> entry);
@@ skipping 3518 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_