Object pool with support for untagged entries.

runtime/vm/deopt_instructions.h

Index: runtime/vm/deopt_instructions.h
diff --git a/runtime/vm/deopt_instructions.h b/runtime/vm/deopt_instructions.h
index 68e92df1f668ffffb8713848a052dd20ea79e612..95206e77af9c442caba190359c51775e3cf35ca2 100644
--- a/runtime/vm/deopt_instructions.h
+++ b/runtime/vm/deopt_instructions.h
@@ -54,8 +54,8 @@ class DeoptContext {
   void SetCallerFp(intptr_t callers_fp);
 
   RawObject* ObjectAt(intptr_t index) const {
-    const Array& object_pool = Array::Handle(object_pool_);
-    return object_pool.At(index);
+    const ObjectPool& object_pool = ObjectPool::Handle(object_pool_);
+    return object_pool.ObjectAt(index);
   }
 
   intptr_t RegisterValue(Register reg) const {
@@ -205,7 +205,7 @@ class DeoptContext {
   }
 
   RawCode* code_;
-  RawArray* object_pool_;
+  RawObjectPool* object_pool_;
   RawTypedData* deopt_info_;
   bool dest_frame_is_allocated_;
   intptr_t* dest_frame_;
@@ -287,7 +287,7 @@ class DeoptInstr : public ZoneAllocated {
   // Get the code and return address which is encoded in this
   // kRetAfterAddress deopt instruction.
   static uword GetRetAddress(DeoptInstr* instr,
-                             const Array& object_pool,
+                             const ObjectPool& object_pool,
                              Code* code);
 
   // Return number of initialized fields in the object that will be