Fix bad optimization of instance-of with uninstantiated types (issue 5216).

runtime/vm/intermediate_language.h

 // Copyright (c) 2012, 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 71 matching lines @@
 
   Value* Copy() { return new Value(definition_); }
 
   RawAbstractType* CompileType() const;
   intptr_t ResultCid() const;
 
   void PrintTo(BufferFormatter* f) const;
 
   const char* DebugName() const { return "Value"; }
 
-  // Returns true if the value represents a constant.
+  // Return true if the value represents a constant.
   bool BindsToConstant() const;
 
-  // Returns true if the value represents the constant null.
+  // Return true if the value represents the constant null.
   bool BindsToConstantNull() const;
 
   // Assert if BindsToConstant() is false, otherwise returns the constant value.
   const Object& BoundConstant() const;
 
-  // Reminder: The type of the constant null is the bottom type, which is more
-  // specific than any type.
-  bool CompileTypeIsMoreSpecificThan(const AbstractType& dst_type) const;
+  // Compute a run-time null test at compile-time and set result in is_null.
+  // Return false if the computation is not possible at compile time.
+  bool CanComputeIsNull(bool* is_null) const;
+
+  // Compute a run-time type test at compile-time and set result in is_instance.
+  // Return false if the computation is not possible at compile time.
+  bool CanComputeIsInstanceOf(const AbstractType& type,
+                              bool* is_instance) const;
 
   // Compile time constants, Bool, Smi and Nulls do not need to update
   // the store buffer.
   bool NeedsStoreBuffer() const;
 
   bool Equals(Value* other) const;
 
   void set_reaching_cid(intptr_t cid) { reaching_cid_ = cid; }
   intptr_t reaching_cid() const { return reaching_cid_; }
 
@@ skipping 3554 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_