[modules] Maintain array of cells for imports and local exports.

src/ast/modules.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_AST_MODULES_H_
 #define V8_AST_MODULES_H_
 
 #include "src/parsing/scanner.h"  // Only for Scanner::Location.
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone/zone-containers.h"
@@ skipping 68 matching lines @@
     const AstRawString* local_name;
     const AstRawString* import_name;
 
     // The module_request value records the order in which modules are
     // requested. It also functions as an index into the ModuleInfo's array of
     // module specifiers and into the Module's array of requested modules.  A
     // negative value means no module request.
     int module_request;
 
     // Import/export entries that are associated with a MODULE-allocated
-    // variable use the cell_index value to encode the location of their cell.
-    // Negative values are used for imports and positive values for exports.
-    // For entries that are not associated with a MODULE-allocated variable,
-    // cell_index is 0.
+    // variable (i.e. regular_imports and regular_exports after Validate) use
+    // the cell_index value to encode the location of their cell.  During
+    // variable allocation, this will be be copied into the variable's index
+    // field.
+    // Entries that are not associated with a MODULE-allocated variable have
+    // cell_index_kind(cell_index) == kInvalid.
     int cell_index;
 
     // TODO(neis): Remove local_name component?
     explicit Entry(Scanner::Location loc)
         : location(loc),
           export_name(nullptr),
           local_name(nullptr),
           import_name(nullptr),
           module_request(-1),
           cell_index(0) {}
 
     // (De-)serialization support.
     // Note that the location value is not preserved as it's only needed by the
     // parser.  (A Deserialize'd entry has an invalid location.)
     Handle<ModuleInfoEntry> Serialize(Isolate* isolate) const;
     static Entry* Deserialize(Isolate* isolate, AstValueFactory* avfactory,
                               Handle<ModuleInfoEntry> entry);
   };
 
+  enum CellIndexKind { kInvalid, kExport, kImport };
+  static CellIndexKind cell_index_kind(int cell_index);

[adamk, 2016/11/03 18:30:45]

The underscore naming for a static method looks a little funny to me, maybe call
this GetCellIndexKind?

[neis, 2016/11/04 10:14:39]

Done.

+
   // Module requests.
   const ZoneMap<const AstRawString*, int>& module_requests() const {
     return module_requests_;
   }
 
   // Namespace imports.
   const ZoneList<const Entry*>& namespace_imports() const {
     return namespace_imports_;
   }
 
@@ skipping 91 matching lines @@
                   .insert(std::make_pair(specifier, module_requests_.size()))
                   .first;
     return it->second;
   }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_MODULES_H_