Remove the obsolete OverwriteMode optimization.

src/arm64/full-codegen-arm64.cc

Index: src/arm64/full-codegen-arm64.cc
diff --git a/src/arm64/full-codegen-arm64.cc b/src/arm64/full-codegen-arm64.cc
index 9ffbf8862c8fbc439b4b8badeea14367fa09a3a0..c5a71b5199676a1db10d35f9d8d1829180af6223 100644
--- a/src/arm64/full-codegen-arm64.cc
+++ b/src/arm64/full-codegen-arm64.cc
@@ -2018,19 +2018,15 @@ void FullCodeGenerator::VisitAssignment(Assignment* expr) {
     __ Push(x0);  // 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.
@@ -2120,7 +2116,6 @@ void FullCodeGenerator::EmitKeyedSuperPropertyLoad(Property* prop) {
 
 void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
                                               Token::Value op,
-                                              OverwriteMode mode,
                                               Expression* left_expr,
                                               Expression* right_expr) {
   Label done, both_smis, stub_call;
@@ -2138,7 +2133,7 @@ void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
 
   __ Bind(&stub_call);
 
-  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op, mode).code();
+  Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), op).code();
   {
     Assembler::BlockPoolsScope scope(masm_);
     CallIC(code, expr->BinaryOperationFeedbackId());
@@ -2218,11 +2213,9 @@ void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
 }
 
 
-void FullCodeGenerator::EmitBinaryOp(BinaryOperation* expr,
-                                     Token::Value op,
-                                     OverwriteMode mode) {
+void FullCodeGenerator::EmitBinaryOp(BinaryOperation* expr, Token::Value op) {
   __ Pop(x1);
-  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.
   {
     Assembler::BlockPoolsScope scope(masm_);
@@ -4530,8 +4523,7 @@ void FullCodeGenerator::VisitCountOperation(CountOperation* expr) {
 
   {
     Assembler::BlockPoolsScope scope(masm_);
-    Handle<Code> code =
-        CodeFactory::BinaryOpIC(isolate(), Token::ADD, NO_OVERWRITE).code();
+    Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), Token::ADD).code();
     CallIC(code, expr->CountBinOpFeedbackId());
     patch_site.EmitPatchInfo();
   }