Fix incorrect behavior noted via asserts

src/coreclr/src/tools/Common/JitInterface/CorInfoImpl.cs

@@ -109,7 +109,7 @@ private IntPtr AllocException(Exception ex)
         [DllImport(JitSupportLibrary)]
         private extern static char* GetExceptionMessage(IntPtr obj);
 
-        private readonly UnboxingMethodDescFactory _unboxingThunkFactory;
+        private static readonly UnboxingMethodDescFactory _unboxingThunkFactory = new UnboxingMethodDescFactory();
 
         public static void Startup()
         {
@@ -125,8 +125,6 @@ public CorInfoImpl()
             }
 
             _unmanagedCallbacks = GetUnmanagedCallbacks(out _keepAlive);
-
-            _unboxingThunkFactory = new UnboxingMethodDescFactory();
         }
 
         public TextWriter Log

src/coreclr/src/tools/Common/JitInterface/UnboxingMethodDesc.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
 using Internal.TypeSystem;
@@ -79,17 +80,22 @@ protected override int CompareToImpl(MethodDesc other, TypeSystemComparer compar
 #endif
     }
 
-    internal class UnboxingMethodDescFactory : Dictionary<MethodDesc, UnboxingMethodDesc>
+    internal class UnboxingMethodDescFactory : ConcurrentDictionary<MethodDesc, UnboxingMethodDesc>
     {
-        public UnboxingMethodDesc GetUnboxingMethod(MethodDesc method)
+        private Func<MethodDesc, UnboxingMethodDesc> _factoryDelegate;
+        private UnboxingMethodDesc CreateUnboxingMethod(MethodDesc method)
         {
-            if (!TryGetValue(method, out UnboxingMethodDesc result))
-            {
-                result = new UnboxingMethodDesc(method, this);
-                Add(method, result);
-            }
+            return new UnboxingMethodDesc(method, this);
+        }
 
-            return result;
+        public UnboxingMethodDescFactory()
+        {
+            _factoryDelegate = CreateUnboxingMethod;
+        }
+
+        public UnboxingMethodDesc GetUnboxingMethod(MethodDesc method)
+        {
+            return GetOrAdd(method, _factoryDelegate);
         }
     }
 

src/coreclr/src/tools/crossgen2/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs

@@ -1882,7 +1882,7 @@ private void embedGenericHandle(ref CORINFO_RESOLVED_TOKEN pResolvedToken, bool
                             MethodDesc md = HandleToObject(pResolvedToken.hMethod);
                             TypeDesc td = HandleToObject(pResolvedToken.hClass);
 
-                            if (td.IsValueType)
+                            if ((td.IsValueType) && !md.Signature.IsStatic)
                             {
                                 md = _unboxingThunkFactory.GetUnboxingMethod(md);
                             }