AstValueFactory: make true, false, null, undefined and "the hole" unique values.

src/ast-value-factory.cc

 // Copyright 2014 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 312 matching lines @@
   AstValue* value =
       new (zone_) AstValue(AstValue::SMI, number);
   if (isolate_) {
     value->Internalize(isolate_);
   }
   values_.Add(value);
   return value;
 }
 
 
+#define GENERATE_VALUE_GETTER(value, initializer) \
+  if (!value) {                                   \
+    value = new (zone_) AstValue(initializer);    \
+    if (isolate_) {                               \
+      value->Internalize(isolate_);               \
+    }                                             \
+    values_.Add(value);                           \
+  }                                               \
+  return value;
+
+
 const AstValue* AstValueFactory::NewBoolean(bool b) {
-  AstValue* value = new (zone_) AstValue(b);
-  if (isolate_) {
-    value->Internalize(isolate_);
+  if (b) {
+    GENERATE_VALUE_GETTER(true_value_, true);
+  } else {
+    GENERATE_VALUE_GETTER(false_value_, false);
   }
-  values_.Add(value);
-  return value;
 }
 
 
 const AstValue* AstValueFactory::NewStringList(
     ZoneList<const AstRawString*>* strings) {
   AstValue* value = new (zone_) AstValue(strings);
   if (isolate_) {
     value->Internalize(isolate_);
   }
   values_.Add(value);
   return value;
 }
 
 
 const AstValue* AstValueFactory::NewNull() {
-  AstValue* value = new (zone_) AstValue(AstValue::NULL_TYPE);
-  if (isolate_) {
-    value->Internalize(isolate_);
-  }
-  values_.Add(value);
-  return value;
+  GENERATE_VALUE_GETTER(null_value_, AstValue::NULL_TYPE);
 }
 
 
 const AstValue* AstValueFactory::NewUndefined() {
-  AstValue* value = new (zone_) AstValue(AstValue::UNDEFINED);
-  if (isolate_) {
-    value->Internalize(isolate_);
-  }
-  values_.Add(value);
-  return value;
+  GENERATE_VALUE_GETTER(undefined_value_, AstValue::UNDEFINED);
 }
 
 
 const AstValue* AstValueFactory::NewTheHole() {
-  AstValue* value = new (zone_) AstValue(AstValue::THE_HOLE);
-  if (isolate_) {
-    value->Internalize(isolate_);
-  }
-  values_.Add(value);
-  return value;
+  GENERATE_VALUE_GETTER(the_hole_value_, AstValue::THE_HOLE);
 }
 
 
+#undef GENERATE_VALUE_GETTER
+
 const AstRawString* AstValueFactory::GetString(
     uint32_t hash, bool is_one_byte, Vector<const byte> literal_bytes) {
   // literal_bytes here points to whatever the user passed, and this is OK
   // because we use vector_compare (which checks the contents) to compare
   // against the AstRawStrings which are in the string_table_. We should not
   // return this AstRawString.
   AstRawString key(is_one_byte, literal_bytes, hash);
   HashMap::Entry* entry = string_table_.Lookup(&key, hash, true);
   if (entry->value == NULL) {
     // Copy literal contents for later comparison.
     int length = literal_bytes.length();
     byte* new_literal_bytes = zone_->NewArray<byte>(length);
     memcpy(new_literal_bytes, literal_bytes.start(), length);
     AstRawString* new_string = new (zone_) AstRawString(
         is_one_byte, Vector<const byte>(new_literal_bytes, length), hash);
     entry->key = new_string;
     strings_.Add(new_string);
     if (isolate_) {
       new_string->Internalize(isolate_);
     }
     entry->value = reinterpret_cast<void*>(1);
   }
   return reinterpret_cast<AstRawString*>(entry->key);
 }
 
 
 } }  // namespace v8::internal