Support string add in crankshaft:

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 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 3290 matching lines @@
 }
 
 
 void LCodeGen::DoStringLength(LStringLength* instr) {
   Register string = ToRegister(instr->string());
   Register result = ToRegister(instr->result());
   __ mov(result, FieldOperand(string, String::kLengthOffset));
 }
 
 
+void LCodeGen::DoStringAdd(LStringAdd* instr) {
+  if (instr->left()->IsConstantOperand()) {
+    __ push(ToImmediate(instr->left()));
+  } else {
+    __ push(ToOperand(instr->left()));
+  }
+  if (instr->right()->IsConstantOperand()) {
+    __ push(ToImmediate(instr->right()));
+  } else {
+    __ push(ToOperand(instr->right()));
+  }
+  StringAddStub stub(NO_STRING_CHECK_IN_STUB);
+  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr, RESTORE_CONTEXT);
+}
+
+
 void LCodeGen::DoInteger32ToDouble(LInteger32ToDouble* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister() || input->IsStackSlot());
   LOperand* output = instr->result();
   ASSERT(output->IsDoubleRegister());
   __ cvtsi2sd(ToDoubleRegister(output), ToOperand(input));
 }
 
 
 void LCodeGen::DoNumberTagI(LNumberTagI* instr) {
@@ skipping 856 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32