Keep x86 tail call via jit helper as a virtual stub call.

src/coreclr/src/jit/assertionprop.cpp

@@ -2168,7 +2168,7 @@ void Compiler::optAssertionGen(GenTree* tree)
             // with a GTF_CALL_NULLCHECK flag set.
             // Ignore tail calls because they have 'this` pointer in the regular arg list and an implicit null check.
             GenTreeCall* const call = tree->AsCall();
-            if (call->NeedsNullCheck() || call->IsVirtual())
+            if (call->NeedsNullCheck() || (call->IsVirtual() && !call->IsTailCall()))
             {
                 //  Retrieve the 'this' arg.
                 GenTree* thisArg = gtGetThisArg(call);

src/coreclr/src/jit/morph.cpp

@@ -8435,6 +8435,10 @@ void Compiler::fgMorphTailCallViaJitHelper(GenTreeCall* call)
             thisPtr = objp;
         }
 
+        // TODO-Cleanup: we leave it as a virtual stub call to
+        // use logic in `LowerVirtualStubCall`, clear GTF_CALL_VIRT_KIND_MASK here
+        // and change `LowerCall` to recognize it as a direct call.
+
         // During rationalization tmp="this" and null check will
         // materialize as embedded stmts in right execution order.
         assert(thisPtr != nullptr);