Merge 6095:6198 from bleeding_edge to experimental/gc.

src/heap.cc

Index: src/heap.cc
===================================================================
--- src/heap.cc	(revision 6170)
+++ src/heap.cc	(working copy)
@@ -2525,20 +2525,10 @@
   }
 
   // For small strings we check whether the resource contains only
-  // ascii characters.  If yes, we use a different string map.
-  bool is_ascii = true;
-  if (length >= static_cast<size_t>(String::kMinNonFlatLength)) {
-    is_ascii = false;
-  } else {
-    const uc16* data = resource->data();
-    for (size_t i = 0; i < length; i++) {
-      if (data[i] > String::kMaxAsciiCharCode) {
-        is_ascii = false;
-        break;
-      }
-    }
-  }
-
+  // ASCII characters.  If yes, we use a different string map.
+  static const size_t kAsciiCheckLengthLimit = 32;
+  bool is_ascii = length <= kAsciiCheckLengthLimit &&
+      String::IsAscii(resource->data(), static_cast<int>(length));
   Map* map = is_ascii ?
       Heap::external_string_with_ascii_data_map() : Heap::external_string_map();
   Object* result;
@@ -3283,8 +3273,8 @@
 }
 
 
-MaybeObject* Heap::AllocateStringFromUtf8(Vector<const char> string,
-                                          PretenureFlag pretenure) {
+MaybeObject* Heap::AllocateStringFromUtf8Slow(Vector<const char> string,
+                                              PretenureFlag pretenure) {
   // V8 only supports characters in the Basic Multilingual Plane.
   const uc32 kMaxSupportedChar = 0xFFFF;
   // Count the number of characters in the UTF-8 string and check if
@@ -3293,17 +3283,11 @@
       decoder(ScannerConstants::utf8_decoder());
   decoder->Reset(string.start(), string.length());
   int chars = 0;
-  bool is_ascii = true;
   while (decoder->has_more()) {
-    uc32 r = decoder->GetNext();
-    if (r > String::kMaxAsciiCharCode) is_ascii = false;
+    decoder->GetNext();
     chars++;
   }
 
-  // If the string is ascii, we do not need to convert the characters
-  // since UTF8 is backwards compatible with ascii.
-  if (is_ascii) return AllocateStringFromAscii(string, pretenure);
-
   Object* result;
   { MaybeObject* maybe_result = AllocateRawTwoByteString(chars, pretenure);
     if (!maybe_result->ToObject(&result)) return maybe_result;
@@ -3324,11 +3308,8 @@
 MaybeObject* Heap::AllocateStringFromTwoByte(Vector<const uc16> string,
                                              PretenureFlag pretenure) {
   // Check if the string is an ASCII string.
-  int i = 0;
-  while (i < string.length() && string[i] <= String::kMaxAsciiCharCode) i++;
-
   MaybeObject* maybe_result;
-  if (i == string.length()) {  // It's an ASCII string.
+  if (String::IsAscii(string.start(), string.length())) {
     maybe_result = AllocateRawAsciiString(string.length(), pretenure);
   } else {  // It's not an ASCII string.
     maybe_result = AllocateRawTwoByteString(string.length(), pretenure);
@@ -4007,6 +3988,36 @@
 }
 
 
+MaybeObject* Heap::LookupAsciiSymbol(Vector<const char> string) {
+  Object* symbol = NULL;
+  Object* new_table;
+  { MaybeObject* maybe_new_table =
+        symbol_table()->LookupAsciiSymbol(string, &symbol);
+    if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
+  }
+  // Can't use set_symbol_table because SymbolTable::cast knows that
+  // SymbolTable is a singleton and checks for identity.
+  roots_[kSymbolTableRootIndex] = new_table;
+  ASSERT(symbol != NULL);
+  return symbol;
+}
+
+
+MaybeObject* Heap::LookupTwoByteSymbol(Vector<const uc16> string) {
+  Object* symbol = NULL;
+  Object* new_table;
+  { MaybeObject* maybe_new_table =
+        symbol_table()->LookupTwoByteSymbol(string, &symbol);
+    if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
+  }
+  // Can't use set_symbol_table because SymbolTable::cast knows that
+  // SymbolTable is a singleton and checks for identity.
+  roots_[kSymbolTableRootIndex] = new_table;
+  ASSERT(symbol != NULL);
+  return symbol;
+}
+
+
 MaybeObject* Heap::LookupSymbol(String* string) {
   if (string->IsSymbol()) return string;
   Object* symbol = NULL;