ARM native string addition.

src/arm/codegen-arm.h

Index: src/arm/codegen-arm.h
diff --git a/src/arm/codegen-arm.h b/src/arm/codegen-arm.h
index 6eb7c964d36e7bedf7c24d59db348a796dfec7bf..2578a398c774b2e9a48026dd7c1f524629cf3c3a 100644
--- a/src/arm/codegen-arm.h
+++ b/src/arm/codegen-arm.h
@@ -537,6 +537,7 @@ class StringStubBase: public CodeStub {
   // be used in places where the number of characters is small and the
   // additional setup and checking in GenerateCopyCharactersLong adds too much
   // overhead. Copying of overlapping regions is not supported.
+  // Dest register ends at the position after the last character written.
   void GenerateCopyCharacters(MacroAssembler* masm,
                               Register dest,
                               Register src,
@@ -547,6 +548,7 @@ class StringStubBase: public CodeStub {
   // Generate code for copying a large number of characters. This function
   // is allowed to spend extra time setting up conditions to make copying
   // faster. Copying of overlapping regions is not supported.
+  // Dest register ends at the position after the last character written.
   void GenerateCopyCharactersLong(MacroAssembler* masm,
                                   Register dest,
                                   Register src,
@@ -567,6 +569,23 @@ enum StringAddFlags {
 };
 
 
+class StringAddStub: public StringStubBase {
+ public:
+  explicit StringAddStub(StringAddFlags flags) {
+    string_check_ = ((flags & NO_STRING_CHECK_IN_STUB) == 0);
+  }
+
+ private:
+  Major MajorKey() { return StringAdd; }
+  int MinorKey() { return string_check_ ? 0 : 1; }
+
+  void Generate(MacroAssembler* masm);
+
+  // Should the stub check whether arguments are strings?
+  bool string_check_;
+};
+
+
 class SubStringStub: public StringStubBase {
  public:
   SubStringStub() {}