For nullable/double typed fields compare with null for deoptimization, else assume double.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 389 matching lines @@
         (ToAbstractType()->Equals(*other->ToAbstractType()));
   }
 
   bool IsNone() const {
     return (cid_ == kIllegalCid) && (type_ == NULL);
   }
 
   void PrintTo(BufferFormatter* f) const;
   const char* ToCString() const;
 
+  intptr_t cid() const { return cid_; }

[Vyacheslav Egorov (Google), 2014/05/02 00:39:24]

There is already ToNullableCid() getter, no need to add this one.

[srdjan, 2014/05/02 15:35:50]

Removed and replaced.

+
  private:
   bool CanComputeIsInstanceOf(const AbstractType& type,
                               bool is_nullable,
                               bool* is_instance);
 
   bool is_nullable_;
   intptr_t cid_;
   const AbstractType* type_;
 };
 
@@ skipping 7520 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_