Added back some utf8 optimizations

R=yangguo@chromium.org
BUG=https://code.google.com/p/v8/issues/detail?id=2551

Review URL: https://codereview.chromium.org/12390057

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13842 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects-inl.h

@@ -2648,6 +2648,32 @@ void String::Visit(
 }
 
 
+// TODO(dcarney): Remove this class after conversion to VisitFlat.
+class ConsStringCaptureOp {
+ public:
+  inline ConsStringCaptureOp() : cons_string_(NULL) {}
+  inline String* Operate(String* string, unsigned*, int32_t*, unsigned*) {
+    cons_string_ = ConsString::cast(string);
+    return NULL;
+  }
+  ConsString* cons_string_;
+};
+
+
+template<class Visitor>
+ConsString* String::VisitFlat(Visitor* visitor,
+                              String* string,
+                              int offset,
+                              int length,
+                              int32_t type) {
+  ASSERT(length >= 0 && length == string->length());
+  ASSERT(offset >= 0 && offset <= length);
+  ConsStringCaptureOp op;
+  Visit(string, offset, *visitor, op, type, static_cast<unsigned>(length));
+  return op.cons_string_;
+}
+
+
 uint16_t SeqOneByteString::SeqOneByteStringGet(int index) {
   ASSERT(index >= 0 && index < length());
   return READ_BYTE_FIELD(this, kHeaderSize + index * kCharSize);

src/objects.h

@@ -7337,6 +7337,8 @@ class Symbol: public Name {
 };
 
 
+class ConsString;
+
 // The String abstract class captures JavaScript string values:
 //
 // Ecma-262:
@@ -7615,6 +7617,7 @@ class String: public Name {
     return NonOneByteStart(chars, length) >= length;
   }
 
+  // TODO(dcarney): Replace all instances of this with VisitFlat.
   template<class Visitor, class ConsOp>
   static inline void Visit(String* string,
                            unsigned offset,
@@ -7623,6 +7626,21 @@ class String: public Name {
                            int32_t type,
                            unsigned length);
 
+  template<class Visitor>
+  static inline ConsString* VisitFlat(Visitor* visitor,
+                                      String* string,
+                                      int offset,
+                                      int length,
+                                      int32_t type);
+
+  template<class Visitor>
+  static inline ConsString* VisitFlat(Visitor* visitor,
+                                      String* string,
+                                      int offset = 0) {
+    int32_t type = string->map()->instance_type();
+    return VisitFlat(visitor, string, offset, string->length(), type);
+  }
+
  private:
   friend class Name;