ARM: Implement native substring copying.

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 4f56c84fc21c89bf768cfe3873fc82c77d6bac41..5673052265bb1f879393dfa1679c93473ed3e5b8 100644
--- a/src/arm/codegen-arm.h
+++ b/src/arm/codegen-arm.h
@@ -529,6 +529,55 @@ class GenericBinaryOpStub : public CodeStub {
 };
 
 
+class StringStubBase: public CodeStub {
+ public:
+  // Generate code for copying characters using a simple loop. This should only
+  // 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.
+  void GenerateCopyCharacters(MacroAssembler* masm,
+                              Register dest,
+                              Register src,
+                              Register count,
+                              Register scratch,
+                              bool ascii);
+
+  // 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.
+  void GenerateCopyCharactersLong(MacroAssembler* masm,
+                                  Register dest,
+                                  Register src,
+                                  Register count,
+                                  Register scratch1,
+                                  Register scratch2,
+                                  Register scratch3,
+                                  Register scratch4,
+                                  Register scratch5,
+                                  int flags);
+};
+
+
+// Flag that indicates how to generate code for the stub StringAddStub.
+enum StringAddFlags {
+  NO_STRING_ADD_FLAGS = 0,
+  NO_STRING_CHECK_IN_STUB = 1 << 0  // Omit string check in stub.
+};
+
+
+class SubStringStub: public StringStubBase {
+ public:
+  SubStringStub() {}
+
+ private:
+  Major MajorKey() { return SubString; }
+  int MinorKey() { return 0; }
+
+  void Generate(MacroAssembler* masm);
+};
+
+
+
 class StringCompareStub: public CodeStub {
  public:
   StringCompareStub() { }