Add contexts.

runtime/vm/flow_graph_builder.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_BUILDER_H_
 #define VM_FLOW_GRAPH_BUILDER_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 
 namespace dart {
 
 class Instruction;
 class ParsedFunction;
 
 // Build a flow graph from a parsed function's AST.
 class FlowGraphBuilder: public ValueObject {
  public:
   explicit FlowGraphBuilder(const ParsedFunction& parsed_function)
       : parsed_function_(parsed_function),
         preorder_block_entries_(),
-        postorder_block_entries_() { }
+        postorder_block_entries_(),
+        context_level_(0) { }
 
   void BuildGraph();
 
   const ParsedFunction& parsed_function() const { return parsed_function_; }
 
   const GrowableArray<BlockEntryInstr*>& postorder_block_entries() const {
     return postorder_block_entries_;
   }
 
   void Bailout(const char* reason);
@@ skipping 103 matching lines @@
   // preparation of a constructor call.
   // May be called only if allocating an object of a parameterized class.
   void BuildConstructorTypeArguments(ConstructorCallNode* node,
                                      intptr_t start_index,
                                      ZoneGrowableArray<Value*>* args);
 
   // Returns the value of the type arguments of the instantiator.
   Value* BuildInstantiatorTypeArguments(intptr_t token_index,
                                         intptr_t start_index);
 
+  bool MustSaveRestoreContext(SequenceNode* node) const;
+
+  // Moves parent context into the context register.
+  void UnchainContext();
+
   void CloseFragment() { exit_ = NULL; }
   intptr_t AllocateTempIndex() { return temp_index_++; }
 
  private:
   // Specify a computation as the final result.  Adds a Do instruction to
   // the graph, but normally overridden in subclasses.
   virtual void ReturnComputation(Computation* computation) {
     AddInstruction(new DoInstr(computation));
   }
 
@@ skipping 113 matching lines @@
   }
 
   // Output parameters.
   TargetEntryInstr** true_successor_address_;
   TargetEntryInstr** false_successor_address_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_BUILDER_H_