L4 removes RRPV array, will not support cross-predictor reuse, will use out-line predictcount and map count array, will not use inline predict count.

StgSharp.Common/HighPerformance/Memory/L4.Exceptions.cs

@@ -42,4 +42,16 @@ namespace StgSharp.HighPerformance.Memory
             : base($"L4 predictor with id {id} is null. Maybe it has been unregistered.") { }
 
     }
+
+    public sealed class L4PredictConflictException : Exception
+    {
+
+        public L4PredictConflictException(
+               nuint basePtr,
+               ushort policy,
+               int current
+        )
+            : base($"L4 predictor with id {current} has already registered a cache line with base pointer {basePtr} and policy {policy}.") { }
+
+    }
 }

StgSharp.Common/HighPerformance/Memory/L4.Prefetch.cs

@@ -93,16 +93,15 @@ namespace StgSharp.HighPerformance.Memory
                         // This branch performs resident-line adoption rather than a simple policy
                         // equality check. Returning true means the current predictor can keep using
                         // the existing cache bytes without a write-back plus re-prefetch cycle.
-                        if (predict.IsSamePolicy(head->Profile, belong))
+                        if (!ReferenceEquals(predict, belong))
                         {
-                            head->Predictor = (short)predictIndex;
+                            throw new L4PredictConflictException(head->Origin, head->Profile, predictId);
                         } else
                         {
                             // Compatibility failed, so the old owner must first flush its view of
                             // the line before the new predictor rematerializes the cache bytes.
-                            belong.WriteBack(head->Origin, head->Profile, new ReadOnlySpan<byte>((byte*)head->Address, (int)head->Size));
+
-                            head->Profile = pHandle.MapPolicy;
+                            _ = Interlocked.Increment(ref head->RemainingPredictionCount);
-                            predict.Prefetch(head->Origin, head->Profile, new Span<byte>((byte*)head->Address, (int)head->Size));
                         }
 
                         #endregion