Reland: Improve smi shift operations and avoid repeated deoptimizations.

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 14713)
+++ runtime/vm/object.h	(working copy)
@@ -2570,6 +2570,8 @@
   uword GetDeoptBeforePcAtDeoptId(intptr_t deopt_id) const;
   uword GetDeoptAfterPcAtDeoptId(intptr_t deopt_id) const;
 
+  uword GetPcForDeoptId(intptr_t deopt_id, PcDescriptors::Kind kind) const;
+
   // Returns true if there is an object in the code between 'start_offset'
   // (inclusive) and 'end_offset' (exclusive).
   bool ObjectExistsInArea(intptr_t start_offest, intptr_t end_offset) const;
@@ -2626,7 +2628,6 @@
     *PointerOffsetAddrAt(index) = offset_in_instructions;
   }
 
-  uword GetPcForDeoptId(intptr_t deopt_id, PcDescriptors::Kind kind) const;
 
   // New is a private method as RawInstruction and RawCode objects should
   // only be created using the Code::FinalizeCode method. This method creates
@@ -2786,6 +2787,12 @@
     return raw_ptr()->deopt_id_;
   }
 
+  intptr_t deopt_reason() const {
+    return raw_ptr()->deopt_reason_;
+  }
+
+  void set_deopt_reason(intptr_t reason) const;
+
   intptr_t NumberOfChecks() const;
 
   static intptr_t InstanceSize() {