Support string add in crankshaft:

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index e6511a788c5c97f2c633e175367518f8305a42c6..275e8e29a1ee5ca8072b0a3d3c310132005c0f09 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -446,6 +446,9 @@ void TypeRecordingBinaryOpStub::Generate(MacroAssembler* masm) {
     case TRBinaryOpIC::ODDBALL:
       GenerateOddballStub(masm);
       break;
+    case TRBinaryOpIC::BOTH_STRING:
+      GenerateBothStringStub(masm);
+      break;
     case TRBinaryOpIC::STRING:
       GenerateStringStub(masm);
       break;
@@ -909,6 +912,38 @@ void TypeRecordingBinaryOpStub::GenerateStringStub(MacroAssembler* masm) {
 }
 
 
+void TypeRecordingBinaryOpStub::GenerateBothStringStub(MacroAssembler* masm) {
+  Label call_runtime;
+  ASSERT(operands_type_ == TRBinaryOpIC::BOTH_STRING);
+  ASSERT(op_ == Token::ADD);
+  // If both arguments are strings, call the string add stub.
+  // Otherwise, do a transition.
+
+  // Registers containing left and right operands respectively.
+  Register left = edx;
+  Register right = eax;
+
+  // Test if left operand is a string.
+  __ test(left, Immediate(kSmiTagMask));
+  __ j(zero, &call_runtime);
+  __ CmpObjectType(left, FIRST_NONSTRING_TYPE, ecx);
+  __ j(above_equal, &call_runtime);
+
+  // Test if right operand is a string.
+  __ test(right, Immediate(kSmiTagMask));
+  __ j(zero, &call_runtime);
+  __ CmpObjectType(right, FIRST_NONSTRING_TYPE, ecx);
+  __ j(above_equal, &call_runtime);
+
+  StringAddStub string_add_stub(NO_STRING_CHECK_IN_STUB);
+  GenerateRegisterArgsPush(masm);
+  __ TailCallStub(&string_add_stub);
+
+  __ bind(&call_runtime);
+  GenerateTypeTransition(masm);
+}
+
+
 void TypeRecordingBinaryOpStub::GenerateInt32Stub(MacroAssembler* masm) {
   Label call_runtime;
   ASSERT(operands_type_ == TRBinaryOpIC::INT32);