Don't flatten every time we call CharCodeAt

src/objects-inl.h

 // 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 160 matching lines @@
 
 
 bool Object::IsConsString() {
   if (!this->IsHeapObject()) return false;
   uint32_t type = HeapObject::cast(this)->map()->instance_type();
   return (type & (kIsNotStringMask | kStringRepresentationMask)) ==
          (kStringTag | kConsStringTag);
 }
 
 
+bool Object::IsFlatString() {
+  if (!this->IsHeapObject()) return false;
+  uint32_t type = HeapObject::cast(this)->map()->instance_type();
+  return (type & (kIsNotStringMask | kStringRepresentationMask)) == kStringTag;
+}
+
+
 bool Object::IsSeqString() {
   if (!IsString()) return false;
   return StringShape(String::cast(this)).IsSequential();
 }
 
 
 bool Object::IsSeqAsciiString() {
   if (!IsString()) return false;
   return StringShape(String::cast(this)).IsSequential() &&
          String::cast(this)->IsAsciiRepresentation();
@@ skipping 1677 matching lines @@
 CAST_ACCESSOR(DescriptorArray)
 CAST_ACCESSOR(DeoptimizationInputData)
 CAST_ACCESSOR(DeoptimizationOutputData)
 CAST_ACCESSOR(SymbolTable)
 CAST_ACCESSOR(JSFunctionResultCache)
 CAST_ACCESSOR(NormalizedMapCache)
 CAST_ACCESSOR(CompilationCacheTable)
 CAST_ACCESSOR(CodeCacheHashTable)
 CAST_ACCESSOR(MapCache)
 CAST_ACCESSOR(String)
+CAST_ACCESSOR(FlatString)
 CAST_ACCESSOR(SeqString)
 CAST_ACCESSOR(SeqAsciiString)
 CAST_ACCESSOR(SeqTwoByteString)
 CAST_ACCESSOR(ConsString)
 CAST_ACCESSOR(ExternalString)
 CAST_ACCESSOR(ExternalAsciiString)
 CAST_ACCESSOR(ExternalTwoByteString)
 CAST_ACCESSOR(JSObject)
 CAST_ACCESSOR(Smi)
 CAST_ACCESSOR(HeapObject)
@@ skipping 79 matching lines @@
 String* String::TryFlattenGetString(PretenureFlag pretenure) {
   MaybeObject* flat = TryFlatten(pretenure);
   Object* successfully_flattened;
   if (flat->ToObject(&successfully_flattened)) {
     return String::cast(successfully_flattened);
   }
   return this;
 }
 
 
+uint16_t FlatString::FlatStringGet(int index) {
+  ASSERT(index >= 0 && index < length());
+  switch (StringShape(this).full_representation_tag()) {
+    case kSeqStringTag | kAsciiStringTag:
+      return SeqAsciiString::cast(this)->SeqAsciiStringGet(index);
+    case kSeqStringTag | kTwoByteStringTag:
+      return SeqTwoByteString::cast(this)->SeqTwoByteStringGet(index);
+    case kExternalStringTag | kAsciiStringTag:
+      return ExternalAsciiString::cast(this)->ExternalAsciiStringGet(index);
+    case kExternalStringTag | kTwoByteStringTag:
+      return ExternalTwoByteString::cast(this)->ExternalTwoByteStringGet(index);
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return 0;
+}
+
+
 uint16_t String::Get(int index) {
   ASSERT(index >= 0 && index < length());
   switch (StringShape(this).full_representation_tag()) {
     case kSeqStringTag | kAsciiStringTag:
       return SeqAsciiString::cast(this)->SeqAsciiStringGet(index);
     case kSeqStringTag | kTwoByteStringTag:
       return SeqTwoByteString::cast(this)->SeqTwoByteStringGet(index);
     case kConsStringTag | kAsciiStringTag:
     case kConsStringTag | kTwoByteStringTag:
       return ConsString::cast(this)->ConsStringGet(index);
     case kExternalStringTag | kAsciiStringTag:
       return ExternalAsciiString::cast(this)->ExternalAsciiStringGet(index);
     case kExternalStringTag | kTwoByteStringTag:
       return ExternalTwoByteString::cast(this)->ExternalTwoByteStringGet(index);
     default:
       break;
   }
-
   UNREACHABLE();
   return 0;
 }
 
 
+MaybeObject* String::GetMayFlatten(int index) {
+  if (this->IsConsString()) {
+    return ConsString::cast(this)->ConsStringGetMayFlatten(index);
+  }
+  return Smi::FromInt(FlatString::cast(this)->FlatStringGet(index));
+}
+
+
 void String::Set(int index, uint16_t value) {
   ASSERT(index >= 0 && index < length());
   ASSERT(StringShape(this).IsSequential());
 
   return this->IsAsciiRepresentation()
       ? SeqAsciiString::cast(this)->SeqAsciiStringSet(index, value)
       : SeqTwoByteString::cast(this)->SeqTwoByteStringSet(index, value);
 }
 
 
@@ skipping 2195 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_