add a repro test.

src/tests/JIT/Regression/JitBlue/Runtime_49780/Runtime_49780.cs

@@ -0,0 +1,36 @@
+// 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.Numerics;
+using System.Diagnostics;
+
+namespace Runtime_49489
+{
+    public class Program
+    {
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        static int Callee(float fltRef0, float fltRef1, float fltReg2, float fltReg3, float fltReg4, float fltReg5, float fltReg6, float fltReg7, Vector2 simd8)
+        {
+            const double eps = 1E-10;
+            Debug.Assert(Math.Abs(simd8.X) <= eps);
+            Debug.Assert(Math.Abs(simd8.Y - 1) <= eps);
+            return 100;
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        static int Caller()
+        {
+            Vector2 simd8;
+            simd8.X = 0;
+            simd8.Y = 1;
+            return Callee(0, 0, 0, 0, 0, 0, 0, 0, simd8);
+
+        }
+
+        static int Main(string[] args)
+        {
+            return Caller();
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_49780/Runtime_49780.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <CLRTestPriority>1</CLRTestPriority>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>