Make one-ascii-character-string a symbol in its cache.

src/heap.cc

 // Copyright 2006-2008 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 1470 matching lines @@
   if (result->IsFailure()) return result;
 
   ExternalTwoByteString* external_string = ExternalTwoByteString::cast(result);
   external_string->set_length(length);
   external_string->set_resource(resource);
 
   return result;
 }
 
 
-Object* Heap:: LookupSingleCharacterStringFromCode(uint16_t code) {
+Object* Heap::LookupSingleCharacterStringFromCode(uint16_t code) {
   if (code <= String::kMaxAsciiCharCode) {
     Object* value = Heap::single_character_string_cache()->get(code);
     if (value != Heap::undefined_value()) return value;
-    Object* result = Heap::AllocateRawAsciiString(1);
+
+    char buffer[1];
+    buffer[0] = static_cast<char>(code);
+    Object* result = LookupSymbol(Vector<const char>(buffer, 1));
+
     if (result->IsFailure()) return result;
-    String::cast(result)->Set(0, code);
     Heap::single_character_string_cache()->set(code, result);
     return result;
   }
+
   Object* result = Heap::AllocateRawTwoByteString(1);

[iposva, 2008/10/21 04:33:46]

Is there a reason we do not symbolize one character two byte strings? Just no
frequent enough?

[Feng Qian, 2008/10/21 16:27:11]

I viewed single_character_string_cache is a cache on top of symbol table, and
two-byte chars are not cached, so I didn't feel strongly to symbolize it.

On 2008/10/21 04:33:46, iposva wrote:

   if (result->IsFailure()) return result;
   String::cast(result)->Set(0, code);
   return result;
 }
 
 
 Object* Heap::AllocateByteArray(int length) {
   int size = ByteArray::SizeFor(length);
   AllocationSpace space =
       size > MaxHeapObjectSize() ? LO_SPACE : NEW_SPACE;
@@ skipping 1597 matching lines @@
 #ifdef DEBUG
 bool Heap::GarbageCollectionGreedyCheck() {
   ASSERT(FLAG_gc_greedy);
   if (Bootstrapper::IsActive()) return true;
   if (disallow_allocation_failure()) return true;
   return CollectGarbage(0, NEW_SPACE);
 }
 #endif
 
 } }  // namespace v8::internal