Optimize identical-comparisons based on propagated type information.

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 348 matching lines @@
   // Recompute compile type.
   virtual void Update() = 0;
 
  protected:
   explicit ConstrainedCompileType(const CompileType& type)
       : ZoneCompileType(type) { }
 };
 
 
 // NotNullConstrainedCompileType represents not-null constraint applied to
-// the source compile type. Result is non-nullable version of the incomming
+// the source compile type. Result is non-nullable version of the incoming
 // compile type. It is used to represent compile type propagated downwards
 // from strict comparison with the null constant.
 class NotNullConstrainedCompileType : public ConstrainedCompileType {
  public:
   explicit NotNullConstrainedCompileType(CompileType* source)
       : ConstrainedCompileType(source->CopyNonNullable()), source_(source) { }
 
   virtual void Update() {
     type_ = source_->CopyNonNullable();
   }
@@ skipping 119 matching lines @@
   // Assert if BindsToConstant() is false, otherwise returns the constant value.
   const Object& BoundConstant() const;
 
   // Compile time constants, Bool, Smi and Nulls do not need to update
   // the store buffer.
   bool NeedsStoreBuffer();
 
   bool Equals(Value* other) const;
 
  private:
+  friend class FlowGraphPrinter;
+
   Definition* definition_;
   Value* previous_use_;
   Value* next_use_;
   Instruction* instruction_;
   intptr_t use_index_;
 
   CompileType* reaching_type_;
 
   DISALLOW_COPY_AND_ASSIGN(Value);
 };
@@ skipping 1226 matching lines @@
 
   void SetReplacement(Definition* other) {
     ASSERT(ssa_temp_index_ >= 0);
     ASSERT(WasEliminated());
     ssa_temp_index_ = kReplacementMarker;
     temp_index_ = reinterpret_cast<intptr_t>(other);
   }
 
  protected:
   friend class RangeAnalysis;
+  friend class Value;
 
   Range* range_;
   CompileType* type_;
 
  private:
   intptr_t temp_index_;
   intptr_t ssa_temp_index_;
   Value* input_use_list_;
   Value* env_use_list_;
   UseKind use_kind_;
@@ skipping 5091 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_