[NativeAOT-LLVM] Fix missing helper info for CORINFO_UNBOX_TYPETEST (…

…dotnet#2659)

* Add a test

* Fix missing helper info for CORINFO_UNBOX_TYPETEST

src/coreclr/jit/llvm.cpp

@@ -326,7 +326,7 @@ bool Llvm::helperCallMayPhysicallyThrow(CorInfoHelpFunc helperFunc) const
         { FUNC(CORINFO_HELP_BOX) CORINFO_TYPE_CLASS, { CORINFO_TYPE_PTR, CORINFO_TYPE_BYREF }, HFIF_SS_ARG },
         { FUNC(CORINFO_HELP_BOX_NULLABLE) CORINFO_TYPE_CLASS, { CORINFO_TYPE_PTR, CORINFO_TYPE_BYREF }, HFIF_SS_ARG },
         { FUNC(CORINFO_HELP_UNBOX) CORINFO_TYPE_BYREF, { CORINFO_TYPE_PTR, CORINFO_TYPE_CLASS }, HFIF_SS_ARG },
-        { FUNC(CORINFO_HELP_UNBOX_TYPETEST) },
+        { FUNC(CORINFO_HELP_UNBOX_TYPETEST) CORINFO_TYPE_VOID, { CORINFO_TYPE_PTR, CORINFO_TYPE_PTR }, HFIF_SS_ARG },
         { FUNC(CORINFO_HELP_UNBOX_NULLABLE) CORINFO_TYPE_VOID, { CORINFO_TYPE_BYREF, CORINFO_TYPE_PTR, CORINFO_TYPE_CLASS }, HFIF_SS_ARG },
 
         // Implemented in "CoreLib\src\Internal\Runtime\CompilerHelpers\TypedReferenceHelpers.cs".

src/tests/nativeaot/SmokeTests/HelloWasm/HelloWasm.cs

@@ -417,6 +417,8 @@ private static unsafe int Main(string[] args)
 
         TestJitUseStruct();
 
+        TestStackAllocatedBox();
+
         TestMismatchedStructLocalFieldStore();
 
         TestUnsafe();
@@ -476,6 +478,25 @@ private unsafe static void TestJitUseStruct()
         EndTest(res.Index == structWithIndex.Index && res.Value == structWithIndex.Value);
     }
 
+    private static void TestStackAllocatedBox()
+    {
+        StartTest("Test a stack-allocated box");
+
+        // Step 1: allocate the box.
+        object box = DayOfWeek.Friday;
+        // Step 2: make sure it appears used to Roslyn, etc.
+        static void Use(ref object _) { }
+        Use(ref box);
+        // Step 3: unbox it as a different type to make sure the Jit
+        // uses the unbox type test helper.
+        if (Environment.GetEnvironmentVariable("NEVER") is "HIT")
+        {
+            _ = (long)box;
+        }
+        // Add in another tricky type test for good measure.
+        EndTest((int)box == (int)DayOfWeek.Friday);
+    }
+
     public struct StructWrapper
     {
         public readonly Guid WrappedStruct;