Add test

src/tests/JIT/Regression/JitBlue/Runtime_105721/Runtime_105721.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+using Xunit;
+
+public class Runtime_105721
+{
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        new Runtime_105721().Foo();
+    }
+
+    private short s_21 = -1;
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private void Foo()
+    {
+        Vector128<short> v1 = Vector128.CreateScalar<short>(s_21);
+        Vector128<int> v2 = Vector128.CreateScalar<int>(s_21);
+        Check(v1, v2);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private void Check(Vector128<short> v1, Vector128<int> v2)
+    {
+        Assert.Equal(-1, v1[0]);
+        Assert.Equal(-1, v2[0]);
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_105721/Runtime_105721.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>