diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index a0e990ccb0..f053c7942c 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -291,6 +291,17 @@ void ElementsTransitionAndStoreStub::InitializeInterfaceDescriptor(
 }
 
 
+void NewStringAddStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { a1, a0 };
+  descriptor->register_param_count_ = 2;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kStringAdd)->entry;
+}
+
+
 #define __ ACCESS_MASM(masm)
 
 
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index 38334d50dd..56c9240dc5 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -3740,11 +3740,20 @@ void FullCodeGenerator::EmitStringCharAt(CallRuntime* expr) {
 void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT_EQ(2, args->length());
-  VisitForStackValue(args->at(0));
-  VisitForStackValue(args->at(1));
+  if (FLAG_new_string_add) {
+    VisitForStackValue(args->at(0));
+    VisitForAccumulatorValue(args->at(1));
 
-  StringAddStub stub(STRING_ADD_CHECK_BOTH);
-  __ CallStub(&stub);
+    __ pop(a1);
+    NewStringAddStub stub(STRING_ADD_CHECK_BOTH, NOT_TENURED);
+    __ CallStub(&stub);
+  } else {
+    VisitForStackValue(args->at(0));
+    VisitForStackValue(args->at(1));
+
+    StringAddStub stub(STRING_ADD_CHECK_BOTH);
+    __ CallStub(&stub);
+  }
   context()->Plug(v0);
 }
 
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 5c2d636d0d..b1cf42cb31 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -4480,10 +4480,18 @@ void LCodeGen::DoTrapAllocationMemento(LTrapAllocationMemento* instr) {
 
 void LCodeGen::DoStringAdd(LStringAdd* instr) {
   ASSERT(ToRegister(instr->context()).is(cp));
-  __ push(ToRegister(instr->left()));
-  __ push(ToRegister(instr->right()));
-  StringAddStub stub(instr->hydrogen()->flags());
-  CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  if (FLAG_new_string_add) {
+    ASSERT(ToRegister(instr->left()).is(a1));
+    ASSERT(ToRegister(instr->right()).is(a0));
+    NewStringAddStub stub(instr->hydrogen()->flags(),
+                          isolate()->heap()->GetPretenureMode());
+    CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  } else {
+    __ push(ToRegister(instr->left()));
+    __ push(ToRegister(instr->right()));
+    StringAddStub stub(instr->hydrogen()->flags());
+    CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  }
 }
 
 
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index edb1206b01..943d9476f4 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2335,8 +2335,12 @@ LInstruction* LChunkBuilder::DoStoreNamedGeneric(HStoreNamedGeneric* instr) {
 
 LInstruction* LChunkBuilder::DoStringAdd(HStringAdd* instr) {
   LOperand* context = UseFixed(instr->context(), cp);
-  LOperand* left = UseRegisterAtStart(instr->left());
-  LOperand* right = UseRegisterAtStart(instr->right());
+  LOperand* left = FLAG_new_string_add
+      ? UseFixed(instr->left(), a1)
+      : UseRegisterAtStart(instr->left());
+  LOperand* right = FLAG_new_string_add
+      ? UseFixed(instr->right(), a0)
+      : UseRegisterAtStart(instr->right());
   return MarkAsCall(
       DefineFixed(new(zone()) LStringAdd(context, left, right), v0),
       instr);