Introduce locations based code generation.

runtime/vm/flow_graph_compiler_x64.h

Index: runtime/vm/flow_graph_compiler_x64.h
diff --git a/runtime/vm/flow_graph_compiler_x64.h b/runtime/vm/flow_graph_compiler_x64.h
index b72a62696bd5457e98b972932f3f0398282cf320..72a6d1d56c158a264b0897e69baeba1277a90e3d 100644
--- a/runtime/vm/flow_graph_compiler_x64.h
+++ b/runtime/vm/flow_graph_compiler_x64.h
@@ -40,6 +40,8 @@ class FlowGraphCompiler : public FlowGraphVisitor {
   void FinalizeExceptionHandlers(const Code& code);
   void FinalizeComments(const Code& code);
 
+  Assembler* assembler() const { return assembler_; }
+
  private:
   static const int kLocalsOffsetFromFP = (-1 * kWordSize);
 
@@ -77,6 +79,9 @@ class FlowGraphCompiler : public FlowGraphVisitor {
 #undef DECLARE_VISIT_COMPUTATION
 #undef DECLARE_VISIT_INSTRUCTION
 
+  void EmitInstructionPrologue(Instruction* instr);
+  void LoadInputs(LocationSummary* summary);
+
   // Emit code to load a Value into register 'dst'.
   void LoadValue(Register dst, Value* value);