Consistently use HStringAdd instead of HCallStub with CodeStub::StringAdd.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 903 matching lines @@
     case CodeStub::SubString: {
       SubStringStub stub;
       CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
       break;
     }
     case CodeStub::NumberToString: {
       NumberToStringStub stub;
       CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
       break;
     }
-    case CodeStub::StringAdd: {
-      StringAddStub stub(NO_STRING_ADD_FLAGS);
-      CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
     case CodeStub::StringCompare: {
       StringCompareStub stub;
       CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
       break;
     }
     case CodeStub::TranscendentalCache: {
       TranscendentalCacheStub stub(instr->transcendental_type(),
                                    TranscendentalCacheStub::TAGGED);
       CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
       break;
@@ skipping 3378 matching lines @@
   Register object = ToRegister(instr->object());
   Register temp = ToRegister(instr->temp());
   __ TestJSArrayForAllocationSiteInfo(object, temp);
   DeoptimizeIf(equal, instr->environment());
 }
 
 
 void LCodeGen::DoStringAdd(LStringAdd* instr) {
   EmitPushTaggedOperand(instr->left());
   EmitPushTaggedOperand(instr->right());
-  StringAddStub stub(NO_STRING_CHECK_IN_STUB);
+  StringAddStub stub(instr->hydrogen()->flags());
   CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
 }
 
 
 void LCodeGen::DoStringCharCodeAt(LStringCharCodeAt* instr) {
   class DeferredStringCharCodeAt: public LDeferredCode {
    public:
     DeferredStringCharCodeAt(LCodeGen* codegen, LStringCharCodeAt* instr)
         : LDeferredCode(codegen), instr_(instr) { }
     virtual void Generate() { codegen()->DoDeferredStringCharCodeAt(instr_); }
@@ skipping 1188 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64