From b3158f3da2f76f1596801c2729dd94aa80cc409a Mon Sep 17 00:00:00 2001
From: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
Date: Thu, 4 Aug 2022 14:08:23 +0100
Subject: [PATCH] Fix performance regression introduced in object
 deserialization

---
 .../Text/Json/Serialization/JsonConverterOfT.cs    | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs
index 02021bdc8eb9f2..7959c76f40f420 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs
@@ -216,6 +216,20 @@ internal bool TryRead(ref Utf8JsonReader reader, Type typeToConvert, JsonSeriali
             bool isContinuation = state.IsContinuation;
             bool success;
 
+            if (
+#if NETCOREAPP
+                !typeof(T).IsValueType &&
+#endif
+                CanBePolymorphic)
+            {
+                // Special case object converters since they don't
+                // require the expensive ReadStack.Push()/Pop() operations.
+                Debug.Assert(this is ObjectConverter);
+                success = OnTryRead(ref reader, typeToConvert, options, ref state, out value);
+                Debug.Assert(success);
+                return true;
+            }
+
 #if DEBUG
             // DEBUG: ensure push/pop operations preserve stack integrity
             JsonTypeInfo originalJsonTypeInfo = state.Current.JsonTypeInfo;