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

src/ast-value-factory.cc

Index: src/ast-value-factory.cc
diff --git a/src/ast-value-factory.cc b/src/ast-value-factory.cc
index 4df6ac01a03a7ddef1fa401c6b0707677bc1950b..0a1949a69cc2b05756aa1939e1d947ebffae2b12 100644
--- a/src/ast-value-factory.cc
+++ b/src/ast-value-factory.cc
@@ -330,13 +330,23 @@ const AstValue* AstValueFactory::NewSmi(int number) {
 }
 
 
+#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;
 }
 
 
@@ -352,35 +362,22 @@ const AstValue* AstValueFactory::NewStringList(
 
 
 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