harmony_scoping: Implement lexical bindings at top level

src/contexts.h

 // Copyright 2012 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_CONTEXTS_H_
 #define V8_CONTEXTS_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 
@@ skipping 165 matching lines @@
   V(NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE, JSFunction,                         \
     native_object_notifier_perform_change)                                     \
   V(SLOPPY_GENERATOR_FUNCTION_MAP_INDEX, Map, sloppy_generator_function_map)   \
   V(STRICT_GENERATOR_FUNCTION_MAP_INDEX, Map, strict_generator_function_map)   \
   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \
   V(ITERATOR_RESULT_MAP_INDEX, Map, iterator_result_map)                       \
   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
   V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map)                             \
   V(ITERATOR_SYMBOL_INDEX, Symbol, iterator_symbol)                            \
   V(UNSCOPABLES_SYMBOL_INDEX, Symbol, unscopables_symbol)                      \
-  V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)
+  V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)            \
+  V(GLOBAL_CONTEXT_TABLE_INDEX, GlobalContextTable, global_context_table)
+
+
+// A table of all global contexts. Every loaded top-level script with top-level
+// lexical declarations contributes its GlobalContext into this table.
+//
+// The table is a fixed array, its first slot is current size and the subsequent
+// slots 1..size contain GlobalContexts.
+class GlobalContextTable : public FixedArray {
+ public:
+  // Conversions.
+  static GlobalContextTable* cast(Object* context) {
+    DCHECK(context->IsGlobalContextTable());
+    return reinterpret_cast<GlobalContextTable*>(context);
+  }
+
+  struct LookupResult {
+    int context_index;
+    int slot_index;
+    VariableMode mode;
+    InitializationFlag init_flag;
+    MaybeAssignedFlag maybe_assigned_flag;
+  };
+
+  int size() const { return Smi::cast(get(kSizeSlot))->value(); }
+
+  static Handle<Context> GetContext(Handle<GlobalContextTable> table, int i) {
+    DCHECK(i < table->size());
+    return Handle<Context>::cast(FixedArray::get(table, i + 1));
+  }
+
+  // Lookup a variable `name` in a GlobalContextTable.
+  // If it returns true, the variable is found and `result` contains
+  // valid information about its location.
+  // If it returns false, `result` is untouched.
+  MUST_USE_RESULT
+  static bool Lookup(Handle<GlobalContextTable> table, Handle<String> name,
+                     LookupResult* result);
+
+  MUST_USE_RESULT
+  static Handle<GlobalContextTable> Extend(Handle<GlobalContextTable> table,
+                                           Handle<Context> global_context);
+
+ private:
+  static const int kSizeSlot = 0;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(GlobalContextTable);
+};
 
 // JSFunctions are pairs (context, function code), sometimes also called
 // closures. A Context object is used to represent function contexts and
 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak).
 //
 // At runtime, the contexts build a stack in parallel to the execution
 // stack, with the top-most context being the current context. All contexts
 // have the following slots:
 //
 // [ closure   ]  This is the current function. It is the same for all
@@ skipping 25 matching lines @@
 //                we always have a context pointer).
 //
 // In addition, function contexts may have statically allocated context slots
 // to store local variables/functions that are accessed from inner functions
 // (via static context addresses) or through 'eval' (dynamic context lookups).
 // The native context contains additional slots for fast access to native
 // properties.
 //
 // Finally, with Harmony scoping, the JSFunction representing a top level
 // script will have the GlobalContext rather than a FunctionContext.
+// Global contexts from all top-level scripts are gathered in
+// GlobalContextTable.
 
 class Context: public FixedArray {
  public:
   // Conversions.
   static Context* cast(Object* context) {
     DCHECK(context->IsContext());
     return reinterpret_cast<Context*>(context);
   }
 
   // The default context slot layout; indices are FixedArray slot indices.
@@ skipping 111 matching lines @@
     NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE,
     SLOPPY_GENERATOR_FUNCTION_MAP_INDEX,
     STRICT_GENERATOR_FUNCTION_MAP_INDEX,
     GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX,
     ITERATOR_RESULT_MAP_INDEX,
     MAP_ITERATOR_MAP_INDEX,
     SET_ITERATOR_MAP_INDEX,
     ITERATOR_SYMBOL_INDEX,
     UNSCOPABLES_SYMBOL_INDEX,
     ARRAY_VALUES_ITERATOR_INDEX,
+    GLOBAL_CONTEXT_TABLE_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.
     OPTIMIZED_FUNCTIONS_LIST,  // Weak.
     OPTIMIZED_CODE_LIST,       // Weak.
     DEOPTIMIZED_CODE_LIST,     // Weak.
     MAP_CACHE_INDEX,           // Weak.
     NEXT_CONTEXT_LINK,         // Weak.
 
     // Total number of slots.
@@ skipping 179 matching lines @@
   static bool IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object);
 #endif
 
   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_CONTEXTS_H_