Skeleton of a linear scan register allocator.

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 0577647532844c80853ff7b61ef75a90853f0ac0..926805a53ff9f39fca74df2f0e996f35bc618487 100644
--- a/runtime/vm/flow_graph_compiler_ia32.h
+++ b/runtime/vm/flow_graph_compiler_ia32.h
@@ -305,6 +305,7 @@ class DeoptimizationStub : public ZoneAllocated {
         try_index_(try_index),
         reason_(reason),
         registers_(2),
+        deoptimization_env_(NULL),
         entry_label_() {}
 
   void Push(Register reg) { registers_.Add(reg); }
@@ -319,6 +320,7 @@ class DeoptimizationStub : public ZoneAllocated {
   const intptr_t try_index_;
   const DeoptReasonId reason_;
   GrowableArray<Register> registers_;
+  const Environment* deoptimization_env_;
   Label entry_label_;
 
   DISALLOW_COPY_AND_ASSIGN(DeoptimizationStub);