[MERGE #5121 @MSLaguana] Adding notion of weak reference regions, and concurrently marking those regions.

Merge pull request #5121 from MSLaguana:recyclerWeakReferenceRegion

Also adding new weak ref region dictionary to make use of this type.

Author: MSLaguana

lib/Common/CommonDefines.h

@@ -263,6 +263,9 @@
 #define RECYCLER_VISITED_HOST
 #endif
 
+
+#define ENABLE_WEAK_REFERENCE_REGIONS 1
+
 // JIT features
 
 #if DISABLE_JIT

lib/Common/DataStructures/BaseDictionary.h

@@ -102,6 +102,8 @@ namespace JsUtil
         Field(int) freeCount;
         Field(int) modFunctionIndex;
 
+        static const int FreeListSentinel = -2;
+
 #if PROFILE_DICTIONARY
         FieldNoBarrier(DictionaryStats*) stats;
 #endif
@@ -780,9 +782,9 @@ namespace JsUtil
 
         static bool IsFreeEntry(const EntryType &entry)
         {
-            // A free entry's next index will be (-2 - nextIndex), such that it is always <= -2, for fast entry iteration
+            // A free entry's next index will be (FreeListSentinel - nextIndex), such that it is always <= FreeListSentinel, for fast entry iteration
             // allowing for skipping over free entries. -1 is reserved for the end-of-chain marker for a used entry.
-            return entry.next <= -2;
+            return entry.next <= FreeListSentinel;
         }
 
         void SetNextFreeEntryIndex(EntryType &freeEntry, const int nextFreeEntryIndex)
@@ -791,15 +793,15 @@ namespace JsUtil
             Assert(nextFreeEntryIndex >= -1);
             Assert(nextFreeEntryIndex < count);
 
-            // The last entry in the free list chain will have a next of -2 to indicate that it is a free entry. The end of the
+            // The last entry in the free list chain will have a next of FreeListSentinel to indicate that it is a free entry. The end of the
             // free list chain is identified using freeCount.
-            freeEntry.next = nextFreeEntryIndex >= 0 ? -2 - nextFreeEntryIndex : -2;
+            freeEntry.next = nextFreeEntryIndex >= 0 ? FreeListSentinel - nextFreeEntryIndex : FreeListSentinel;
         }
 
         static int GetNextFreeEntryIndex(const EntryType &freeEntry)
         {
             Assert(IsFreeEntry(freeEntry));
-            return -2 - freeEntry.next;
+            return FreeListSentinel - freeEntry.next;
         }
 
         template <typename LookupType>
@@ -1327,8 +1329,8 @@ namespace JsUtil
                 bucketIndex(0u - 1)
             #if DBG
                 ,
-                previousEntryIndexInBucket(-2),
-                indexOfEntryAfterRemovedEntry(-2)
+                previousEntryIndexInBucket(FreeListSentinel),
+                indexOfEntryAfterRemovedEntry(FreeListSentinel)
             #endif
             {
                 if(dictionary.Count() != 0)
@@ -1345,9 +1347,9 @@ namespace JsUtil
                 Assert(this->entryIndex >= -1);
                 Assert(this->entryIndex < dictionary.count);
                 Assert(bucketIndex == 0u - 1 || bucketIndex <= bucketCount);
-                Assert(previousEntryIndexInBucket >= -2);
+                Assert(previousEntryIndexInBucket >= FreeListSentinel);
                 Assert(previousEntryIndexInBucket < dictionary.count);
-                Assert(indexOfEntryAfterRemovedEntry >= -2);
+                Assert(indexOfEntryAfterRemovedEntry >= FreeListSentinel);
                 Assert(indexOfEntryAfterRemovedEntry < dictionary.count);
 
                 return Base::IsValid() && this->entryIndex >= 0;

lib/Common/DataStructures/DictionaryEntry.h

@@ -118,11 +118,23 @@ namespace JsUtil
         TKey const& Key() const  { return key; }
     };
 
+    template <class TKey>
+    class BaseKeyEntry : public ValueEntry<TKey>
+    {
+    public:
+        TKey const& Key() const { return this->value; }
+    };
+
     template <class TKey, class TValue>
     class KeyValueEntry : public BaseKeyValueEntry<TKey, TValue>
     {
     };
 
+    template <class TKey>
+    class KeyEntry : public BaseKeyEntry<TKey>
+    {
+    };
+
     template <class TKey, class TValue>
     class KeyValueEntry<TKey*, TValue> : public BaseKeyValueEntry<TKey*, TValue>
     {
@@ -167,6 +179,28 @@ namespace JsUtil
         }
     };
 
+    template <class TKey, template <class K> class THashKeyEntry>
+    class DefaultHashedKeyEntry : public THashKeyEntry<TKey>
+    {
+    public:
+        template<typename Comparer, typename TLookup>
+        inline bool KeyEquals(TLookup const& otherKey, hash_t otherHashCode)
+        {
+            return Comparer::Equals(this->Key(), otherKey);
+        }
+
+        template<typename Comparer>
+        inline hash_t GetHashCode()
+        {
+            return ((Comparer::GetHashCode(this->Key()) & 0x7fffffff) << 1) | 1;
+        }
+
+        void Set(TKey const& key, int hashCode)
+        {
+            __super::Set(key);
+        }
+    };
+
     template <class TKey, class TValue, template <class K, class V> class THashEntry>
     class CacheHashedEntry : public THashEntry<TKey, TValue>
     {
@@ -234,4 +268,7 @@ namespace JsUtil
             return (weakReference == nullptr || weakReference->Get() == nullptr);
         }
     };
+
+    template <class TKey>
+    class SimpleDictionaryKeyEntry : public DefaultHashedKeyEntry<TKey, KeyEntry> {};
 }