Track representations of fields

src/property-details.h

Index: src/property-details.h
diff --git a/src/property-details.h b/src/property-details.h
index 2aa6dcfa959421d8c6e285d3b731fccb6dbc4b31..3ac33b3d4690e6bcd2d9f08159c51740440fab1e 100644
--- a/src/property-details.h
+++ b/src/property-details.h
@@ -76,6 +76,23 @@ enum PropertyType {
 };
 
 
+enum StorageType {
+  TAGGED                    = 0,
+  SMI                       = 1,
+  DOUBLE                    = 2,
+  ANY                       = 3
+};
+
+
+inline bool IsMoreGeneralStorageType(StorageType first, StorageType second) {
+  ASSERT(second != ANY);
+  if (first == ANY) return false;
+  if (second == TAGGED) return false;
+  if (first == DOUBLE) return second == SMI;
+  return first != SMI;
+}
+
+
 // PropertyDetails captures type and attributes for a property.
 // They are used both in property dictionaries and instance descriptors.
 class PropertyDetails BASE_EMBEDDED {
@@ -84,6 +101,7 @@ class PropertyDetails BASE_EMBEDDED {
                   PropertyType type,
                   int index = 0) {
     value_ = TypeField::encode(type)
+        | StorageTypeField::encode(TAGGED)
         | AttributesField::encode(attributes)
         | DictionaryStorageField::encode(index);
 
@@ -96,6 +114,10 @@ class PropertyDetails BASE_EMBEDDED {
 
   PropertyDetails set_pointer(int i) { return PropertyDetails(value_, i); }
 
+  PropertyDetails set_storage_type(StorageType storage) {
+    return PropertyDetails(value_, storage);
+  }
+
   // Conversion for storing details as Object*.
   explicit inline PropertyDetails(Smi* smi);
   inline Smi* AsSmi();
@@ -114,6 +136,10 @@ class PropertyDetails BASE_EMBEDDED {
     return DescriptorStorageField::decode(value_);
   }
 
+  StorageType storage_type() {
+    return StorageTypeField::decode(value_);
+  }
+
   inline PropertyDetails AsDeleted();
 
   static bool IsValidIndex(int index) {
@@ -133,12 +159,16 @@ class PropertyDetails BASE_EMBEDDED {
   class DictionaryStorageField:   public BitField<uint32_t,           7, 24> {};
   class DescriptorStorageField:   public BitField<uint32_t,           7, 11> {};
   class DescriptorPointer:        public BitField<uint32_t,          18, 11> {};
+  class StorageTypeField:         public BitField<StorageType,       29,  2> {};
 
   static const int kInitialIndex = 1;
 
  private:
   PropertyDetails(int value, int pointer) {
-      value_ = DescriptorPointer::update(value, pointer);
+    value_ = DescriptorPointer::update(value, pointer);
+  }
+  PropertyDetails(int value, StorageType storage) {
+    value_ = StorageTypeField::update(value, storage);
   }
 
   uint32_t value_;