Remove the obsolete OverwriteMode optimization.

src/ast.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_AST_H_
 #define V8_AST_H_
 
 #include "src/v8.h"
 
 #include "src/assembler.h"
@@ skipping 319 matching lines @@
 
   // Helpers for ToBoolean conversion.
   virtual bool ToBooleanIsTrue() const { return false; }
   virtual bool ToBooleanIsFalse() const { return false; }
 
   // Symbols that cannot be parsed as array indices are considered property
   // names.  We do not treat symbols that can be array indexes as property
   // names because [] for string objects is handled only by keyed ICs.
   virtual bool IsPropertyName() const { return false; }
 
-  // True iff the result can be safely overwritten (to avoid allocation).
-  // False for operations that can return one of their operands.
-  virtual bool ResultOverwriteAllowed() const { return false; }
-
   // True iff the expression is a literal represented as a smi.
   bool IsSmiLiteral() const;
 
   // True iff the expression is a string literal.
   bool IsStringLiteral() const;
 
   // True iff the expression is the null literal.
   bool IsNullLiteral() const;
 
   // True if we can prove that the expression is the undefined literal.
@@ skipping 1717 matching lines @@
 
   Token::Value op_;
   Expression* expression_;
 };
 
 
 class BinaryOperation FINAL : public Expression {
  public:
   DECLARE_NODE_TYPE(BinaryOperation)
 
-  bool ResultOverwriteAllowed() const OVERRIDE;
-
   Token::Value op() const { return static_cast<Token::Value>(op_); }
   Expression* left() const { return left_; }
   Expression* right() const { return right_; }
   Handle<AllocationSite> allocation_site() const { return allocation_site_; }
   void set_allocation_site(Handle<AllocationSite> allocation_site) {
     allocation_site_ = allocation_site;
   }
 
   // The short-circuit logical operations need an AST ID for their
   // right-hand subexpression.
@@ skipping 1465 matching lines @@
 
  private:
   Zone* zone_;
   AstValueFactory* ast_value_factory_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_