Remove the obsolete OverwriteMode optimization.

src/full-codegen.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/ast-numbering.h"
 #include "src/code-factory.h"
 #include "src/codegen.h"
@@ skipping 1034 matching lines @@
   VisitInDuplicateContext(right);
   __ bind(&done);
 }
 
 
 void FullCodeGenerator::VisitArithmeticExpression(BinaryOperation* expr) {
   Token::Value op = expr->op();
   Comment cmnt(masm_, "[ ArithmeticExpression");
   Expression* left = expr->left();
   Expression* right = expr->right();
-  OverwriteMode mode =
-      left->ResultOverwriteAllowed()
-      ? OVERWRITE_LEFT
-      : (right->ResultOverwriteAllowed() ? OVERWRITE_RIGHT : NO_OVERWRITE);
 
   VisitForStackValue(left);
   VisitForAccumulatorValue(right);
 
   SetSourcePosition(expr->position());
   if (ShouldInlineSmiCase(op)) {
-    EmitInlineSmiBinaryOp(expr, op, mode, left, right);
+    EmitInlineSmiBinaryOp(expr, op, left, right);
   } else {
-    EmitBinaryOp(expr, op, mode);
+    EmitBinaryOp(expr, op);
   }
 }
 
 
 void FullCodeGenerator::VisitBlock(Block* stmt) {
   Comment cmnt(masm_, "[ Block");
   NestedBlock nested_block(this, stmt);
   SetStatementPosition(stmt);
 
   {
@@ skipping 750 matching lines @@
   }
   codegen_->PrepareForBailoutForId(exit_id_, NO_REGISTERS);
   codegen_->scope_ = saved_scope_;
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal