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

runtime/vm/flow_graph_compiler_ia32.h

Index: runtime/vm/flow_graph_compiler_ia32.h
diff --git a/runtime/vm/flow_graph_compiler_ia32.h b/runtime/vm/flow_graph_compiler_ia32.h
index 00274b49ae8f8d018a5d1ae5dae030352c6dcdbb..3fab0877db428f7883e2ba6b7d37b0ebcfda5a6c 100644
--- a/runtime/vm/flow_graph_compiler_ia32.h
+++ b/runtime/vm/flow_graph_compiler_ia32.h
@@ -191,6 +191,8 @@ class FlowGraphCompiler : public ValueObject {
                       Register reg2 = kNoRegister,
                       Register reg3 = kNoRegister);
 
+  void AddSlowPathCode(SlowPathCode* slow_path);
+
   void FinalizeExceptionHandlers(const Code& code);
   void FinalizePcDescriptors(const Code& code);
   void FinalizeDeoptInfo(const Code& code);
@@ -206,6 +208,9 @@ class FlowGraphCompiler : public ValueObject {
     return &frame_register_allocator_;
   }
 
+  void SaveLiveRegisters(LocationSummary* locs);
+  void RestoreLiveRegisters(LocationSummary* locs);
+
   // Returns true if the compiled function has a finally clause.
   bool HasFinally() const;
 
@@ -305,6 +310,7 @@ class FlowGraphCompiler : public ValueObject {
   StackmapTableBuilder* stackmap_table_builder_;
   GrowableArray<BlockInfo*> block_info_;
   GrowableArray<DeoptimizationStub*> deopt_stubs_;
+  GrowableArray<SlowPathCode*> slow_path_code_;
   const GrowableObjectArray& object_table_;
   const bool is_optimizing_;
   const bool is_ssa_;