Optimize function at its entry instead of at exit.

runtime/vm/flow_graph_compiler_ia32.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_IA32_H_
 #define VM_FLOW_GRAPH_COMPILER_IA32_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_ia32.h.
 #endif
@@ skipping 222 matching lines @@
 
   // Array/list element address computations.
   static FieldAddress ElementAddressForIntIndex(intptr_t cid,
                                                 Register array,
                                                 intptr_t offset);
   static FieldAddress ElementAddressForRegIndex(intptr_t cid,
                                                 Register array,
                                                 Register index);
 
  private:
+  void EmitFrameEntry();
+
   void AddStaticCallTarget(const Function& function);
 
   void GenerateDeferredCode();
 
   void EmitInstructionPrologue(Instruction* instr);
   void EmitInstructionEpilogue(Instruction* instr);
 
   // Emit code to load a Value into register 'dst'.
   void LoadValue(Register dst, Value* value);
 
@@ skipping 100 matching lines @@
   // that should be used when deoptimizing we store it in this variable.
   // In future AddDeoptStub should be moved out of the instruction template.
   Environment* pending_deoptimization_env_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_IA32_H_