Remove the obsolete OverwriteMode optimization.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 6815838e2b0feac3a7df6c03e9c1b3eb134015ec..917764bd9a1af09f57ce06915156d43c313b36ed 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -1997,19 +1997,15 @@ void FullCodeGenerator::VisitAssignment(Assignment* expr) {
     __ Push(rax);  // Left operand goes on the stack.
     VisitForAccumulatorValue(expr->value());
 
-    OverwriteMode mode = expr->value()->ResultOverwriteAllowed()
-        ? OVERWRITE_RIGHT
-        : NO_OVERWRITE;
     SetSourcePosition(expr->position() + 1);
     AccumulatorValueContext context(this);
     if (ShouldInlineSmiCase(op)) {
       EmitInlineSmiBinaryOp(expr->binary_operation(),
                             op,
-                            mode,
                             expr->target(),
                             expr->value());
     } else {
-      EmitBinaryOp(expr->binary_operation(), op, mode);
+      EmitBinaryOp(expr->binary_operation(), op);
     }
     // Deoptimization point in case the binary operation may have side effects.
     PrepareForBailout(expr->binary_operation(), TOS_REG);
@@ -2389,7 +2385,6 @@ void FullCodeGenerator::EmitKeyedSuperPropertyLoad(Property* prop) {
 
 void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
                                               Token::Value op,
-                                              OverwriteMode mode,
                                               Expression* left,
                                               Expression* right) {
   // Do combined smi check of the operands. Left operand is on the
@@ -2404,7 +2399,7 @@ void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
 
   __ bind(&stub_call);
   __ movp(rax, rcx);
-  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op, mode).code();
+  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op).code();
   CallIC(code, expr->BinaryOperationFeedbackId());
   patch_site.EmitPatchInfo();
   __ jmp(&done, Label::kNear);
@@ -2504,11 +2499,9 @@ void FullCodeGenerator::EmitClassDefineProperties(ClassLiteral* lit) {
 }
 
 
-void FullCodeGenerator::EmitBinaryOp(BinaryOperation* expr,
-                                     Token::Value op,
-                                     OverwriteMode mode) {
+void FullCodeGenerator::EmitBinaryOp(BinaryOperation* expr, Token::Value op) {
   __ Pop(rdx);
-  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op, mode).code();
+  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op).code();
   JumpPatchSite patch_site(masm_);    // unbound, signals no inlined smi code.
   CallIC(code, expr->BinaryOperationFeedbackId());
   patch_site.EmitPatchInfo();
@@ -4799,8 +4792,8 @@ void FullCodeGenerator::VisitCountOperation(CountOperation* expr) {
   __ bind(&stub_call);
   __ movp(rdx, rax);
   __ Move(rax, Smi::FromInt(1));
-  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), expr->binary_op(),
-                                              NO_OVERWRITE).code();
+  Handle<Code> code =
+      CodeFactory::BinaryOpIC(isolate(), expr->binary_op()).code();
   CallIC(code, expr->CountBinOpFeedbackId());
   patch_site.EmitPatchInfo();
   __ bind(&done);