Implement basic support for deferred slow path code with calls that save and restore live registers.

runtime/vm/flow_graph_compiler.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_H_
 #define VM_FLOW_GRAPH_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
@@ skipping 154 matching lines @@
   const intptr_t deopt_id_;
   const intptr_t try_index_;
   const DeoptReasonId reason_;
   GrowableArray<Register> registers_;
   const Environment* deoptimization_env_;
   Label entry_label_;
 
   DISALLOW_COPY_AND_ASSIGN(DeoptimizationStub);
 };
 
+
+class SlowPathCode : public ZoneAllocated {
+ public:
+  SlowPathCode() : entry_label_(), exit_label_() { }
+
+  Label* entry_label() { return &entry_label_; }
+  Label* exit_label() { return &exit_label_; }
+
+  virtual void EmitNativeCode(FlowGraphCompiler* compiler) = 0;
+
+ private:
+  Label entry_label_;
+  Label exit_label_;
+
+  DISALLOW_COPY_AND_ASSIGN(SlowPathCode);
+};
+
+
 }  // namespace dart
 
 #if defined(TARGET_ARCH_IA32)
 #include "vm/flow_graph_compiler_ia32.h"
 #elif defined(TARGET_ARCH_X64)
 #include "vm/flow_graph_compiler_x64.h"
 #elif defined(TARGET_ARCH_ARM)
 #include "vm/flow_graph_compiler_arm.h"
 #else
 #error Unknown architecture.
 #endif
 
 #endif  // VM_FLOW_GRAPH_COMPILER_H_