IL shift amount test

EmitTest.cs

using System;
using System.Reflection;
using System.Reflection.Emit;

namespace EmitTest
{
    class EmitTest
    {
        static void Main(string[] args)
        {
            var assembly = AssemblyBuilder.DefineDynamicAssembly(
                new AssemblyName("TestAssembly"),
                AssemblyBuilderAccess.Run
            );
            var module = assembly.DefineDynamicModule("TestModule");
            var cls = module.DefineType("TestClass", TypeAttributes.Public | TypeAttributes.Class);

            {
                // int64 TestNoConv(int64 a, int64 b);
                var method = cls.DefineMethod(
                    "TestNoConv",
                    MethodAttributes.Public | MethodAttributes.Static,
                    typeof(long),
                    new Type[] { typeof(long), typeof(long) }
                );
                var il = method.GetILGenerator();
                // return a << b;
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(OpCodes.Shl);
                il.Emit(OpCodes.Ret);
            }

            {
                // int64 TestInt32(int64 a, int64 b);
                var method = cls.DefineMethod(
                    "TestInt32",
                    MethodAttributes.Public | MethodAttributes.Static,
                    typeof(long),
                    new Type[] { typeof(long), typeof(long) }
                );
                var il = method.GetILGenerator();
                // return a << (int32)b;
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(OpCodes.Conv_I4);
                il.Emit(OpCodes.Shl);
                il.Emit(OpCodes.Ret);
            }

            {
                // int64 TestNativeInt(int64 a, int64 b);
                var method = cls.DefineMethod(
                    "TestNativeInt",
                    MethodAttributes.Public | MethodAttributes.Static,
                    typeof(long),
                    new Type[] { typeof(long), typeof(long) }
                );
                var il = method.GetILGenerator();
                // return a << (native int)b;
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(OpCodes.Conv_I);
                il.Emit(OpCodes.Shl);
                il.Emit(OpCodes.Ret);
            }

            var type = cls.CreateType();
            Test(type, "TestNoConv");
            Test(type, "TestInt32");
            Test(type, "TestNativeInt");
        }

        static void Test(Type type, string name)
        {
            Console.Write(name + ": ");
            try
            {
                var m = type.GetMethod(name);
                Console.WriteLine(m.Invoke(null, new object[] { (long)10, (long)1 }));
            }
            catch (Exception)
            {
                Console.WriteLine("Exception occured!");
            }
        }
    }
}

Result_mono6.12.0.107

TestNoConv: Exception occured!
TestInt32: 20
TestNativeInt: 20

Result_NetCore3.1

TestNoConv: 20
TestInt32: 20
TestNativeInt: 20