First step toward an optimizing compiler:

runtime/vm/flow_graph_compiler_x64.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_COMPILER_X64_H_
 #define VM_FLOW_GRAPH_COMPILER_X64_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
 #endif
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/code_descriptors.h"
 #include "vm/code_generator.h"
 #include "vm/intermediate_language.h"
 
 namespace dart {
 
 class Code;
+class DeoptimizationStub;
 class ExceptionHandlerList;
 template <typename T> class GrowableArray;
 class ParsedFunction;
 
 class FlowGraphCompiler : public FlowGraphVisitor {
  public:
   FlowGraphCompiler(Assembler* assembler,
                     const ParsedFunction& parsed_function,
                     const GrowableArray<BlockEntryInstr*>& block_order,
                     bool is_optimizing);
 
   virtual ~FlowGraphCompiler();
 
   void CompileGraph();
 
   // Infrastructure copied from class CodeGenerator or stubbed out.
   void FinalizePcDescriptors(const Code& code);
   void FinalizeStackmaps(const Code& code);
   void FinalizeVarDescriptors(const Code& code);
   void FinalizeExceptionHandlers(const Code& code);
   void FinalizeComments(const Code& code);
 
   Assembler* assembler() const { return assembler_; }
 
+  Label* AddDeoptStub(intptr_t deopt_id,
+                      intptr_t deopt_token_index,
+                      intptr_t try_index_,
+                      DeoptReasonId reason,
+                      Register reg1,
+                      Register reg2);
+
  private:
+  friend class DeoptimizationStub;
+
   // TODO(fschneider): Clean up friend-class declarations once all code
   // generator templates have been moved to intermediate_language_x64.cc.
 #define DECLARE_FRIEND(ShortName, ClassName) friend class ClassName;
   FOR_EACH_COMPUTATION(DECLARE_FRIEND)
 #undef DECLARE_FRIEND
 
   static const int kLocalsOffsetFromFP = (-1 * kWordSize);
 
   // Constructor is lighweight, major initialization work should occur here.
   // This makes it easier to measure time spent in the compiler.
@@ skipping 117 matching lines @@
 
   void CopyParameters();
 
   intptr_t StackSize() const;
 
   bool TryIntrinsify();
   void IntrinsifyGetter();
   void IntrinsifySetter();
   static bool CanOptimize();
 
+  void GenerateDeferredCode();
+
   Assembler* assembler_;
   const ParsedFunction& parsed_function_;
 
   // Compiler specific per-block state.  Indexed by postorder block number
   // for convenience.  This is not the block's index in the block order,
   // which is reverse postorder.
   GrowableArray<BlockInfo*> block_info_;
   BlockEntryInstr* current_block_;
   DescriptorList* pc_descriptors_list_;
   ExceptionHandlerList* exception_handlers_list_;
+  GrowableArray<DeoptimizationStub*> deopt_stubs_;
   const bool is_optimizing_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_X64_H_