Generate some intrinsics using our IR.

runtime/vm/flow_graph_compiler.h

Index: runtime/vm/flow_graph_compiler.h
===================================================================
--- runtime/vm/flow_graph_compiler.h	(revision 39909)
+++ runtime/vm/flow_graph_compiler.h	(working copy)
@@ -292,6 +292,10 @@
   bool CanOSRFunction() const;
   bool is_optimizing() const { return is_optimizing_; }
 
+  void EnterIntrinsicMode();
+  void ExitIntrinsicMode();
+  bool intrinsic_mode() const { return intrinsic_mode_; }
+
   bool ForceSlowPathForStackOverflow() const;
 
   const GrowableArray<BlockInfo*>& block_info() const { return block_info_; }
@@ -620,6 +624,9 @@
   const bool is_optimizing_;
   // Set to true if optimized code has IC calls.
   bool may_reoptimize_;
+  // True while emitting intrinsic code.
+  bool intrinsic_mode_;
+  Label intrinsic_deopt_label_;
 
   const Class& double_class_;
   const Class& mint_class_;