Lower simplified StringAdd to stub call.

test/cctest/compiler/test-simplified-lowering.cc

 // Copyright 2014 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 <limits>
 
 #include "src/compiler/access-builder.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/generic-node-inl.h"
 #include "src/compiler/graph-visualizer.h"
@@ skipping 1033 matching lines @@
 
 
 TEST(LowerReferenceEqual_to_wordeq) {
   TestingGraph t(Type::Any(), Type::Any());
   IrOpcode::Value opcode =
       static_cast<IrOpcode::Value>(t.machine()->WordEqual()->opcode());
   t.CheckLoweringBinop(opcode, t.simplified()->ReferenceEqual(Type::Any()));
 }
 
 
-TEST(LowerStringOps_to_rtcalls) {
-  if (false) {  // TODO(titzer): lower StringOps to runtime calls
-    TestingGraph t(Type::String(), Type::String());
+TEST(LowerStringOps_to_calls) {
+  TestingGraph t(Type::String(), Type::String());
+  if (false) {  // TODO(titzer): lower StringOps to stub/runtime calls
     t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringEqual());
     t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringLessThan());
     t.CheckLoweringBinop(IrOpcode::kCall,
                          t.simplified()->StringLessThanOrEqual());
-    t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringAdd());
   }
+  t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringAdd());
 }
 
 
 void CheckChangeInsertion(IrOpcode::Value expected, MachineType from,
                           MachineType to) {
   TestingGraph t(Type::Any());
   Node* in = t.ExampleWithOutput(from);
   Node* use = t.Use(in, to);
   t.Return(use);
   t.Lower();
@@ skipping 335 matching lines @@
 
   Node* store = t.graph()->NewNode(t.simplified()->StoreField(access), t.p0,
                                    t.p1, t.start, t.start);
   t.Effect(store);
   t.Lower();
 
   CHECK_EQ(IrOpcode::kStore, store->opcode());
   CHECK_EQ(t.p0, store->InputAt(0));
   CheckChangeOf(IrOpcode::kChangeTaggedToFloat64, t.p1, store->InputAt(2));
 }