Improve smi shift operations and avoid repeated deoptimizations.

runtime/vm/deopt_instructions.h

Index: runtime/vm/deopt_instructions.h
===================================================================
--- runtime/vm/deopt_instructions.h	(revision 14704)
+++ runtime/vm/deopt_instructions.h	(working copy)
@@ -7,6 +7,7 @@
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
+#include "vm/code_generator.h"
 #include "vm/growable_array.h"
 #include "vm/object.h"
 
@@ -24,7 +25,8 @@
   DeoptimizationContext(intptr_t* to_frame_start,
                         intptr_t to_frame_size,
                         const Array& object_table,
-                        intptr_t num_args);
+                        intptr_t num_args,
+                        DeoptReasonId deopt_reason);
 
   intptr_t* GetFromFrameAddressAt(intptr_t index) const {
     ASSERT((0 <= index) && (index < from_frame_size_));
@@ -62,6 +64,8 @@
 
   intptr_t from_frame_size() const { return from_frame_size_; }
 
+  DeoptReasonId deopt_reason() const { return deopt_reason_; }
+
  private:
   const Array& object_table_;
   intptr_t* to_frame_;
@@ -71,6 +75,7 @@
   intptr_t* registers_copy_;
   double* xmm_registers_copy_;
   const intptr_t num_args_;
+  const DeoptReasonId deopt_reason_;
   intptr_t caller_fp_;
   Isolate* isolate_;