Implement IsNullCheck for CheckClassInstr. If input is nullable expected type, then check for null …

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 6312 matching lines @@
   virtual bool CanDeoptimize() const { return true; }
 
   Value* value() const { return inputs_[0]; }
 
   const ICData& unary_checks() const { return unary_checks_; }
 
   virtual Instruction* Canonicalize(FlowGraph* flow_graph);
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  void set_null_check(bool flag) { null_check_ = flag; }
-
-  bool null_check() const { return null_check_; }
+  bool IsNullCheck() const;
 
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Effects() const { return EffectSet::None(); }
   virtual EffectSet Dependencies() const;
   virtual bool AttributesEqual(Instruction* other) const;
 
   virtual bool MayThrow() const { return false; }
 
  private:
   const ICData& unary_checks_;
 
-  bool null_check_;
-
   DISALLOW_COPY_AND_ASSIGN(CheckClassInstr);
 };
 
 
 class CheckSmiInstr : public TemplateInstruction<1> {
  public:
   CheckSmiInstr(Value* value, intptr_t original_deopt_id) {
     ASSERT(original_deopt_id != Isolate::kNoDeoptId);
     SetInputAt(0, value);
     deopt_id_ = original_deopt_id;
@@ skipping 283 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_