diff --git a/clang/test/SemaTemplate/temp-param-subst-linear.cpp b/clang/test/SemaTemplate/temp-param-subst-linear.cpp
new file mode 100644
index 0000000..fd93aa5
--- /dev/null
+++ b/clang/test/SemaTemplate/temp-param-subst-linear.cpp
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 -std=c++17 %s -verify
+// expected-no-diagnostics
+
+// This test attempts to ensure that the below template parameter pack
+// splitting technique executes in linear time in the number of template
+// parameters. The size of the list below is selected so as to execute
+// relatively quickly on a "good" compiler and to time out otherwise.
+
+template<typename...> struct TypeList;
+
+namespace detail {
+template<unsigned> using Unsigned = unsigned;
+template<typename T, T ...N> using ListOfNUnsignedsImpl = TypeList<Unsigned<N>...>;
+template<unsigned N> using ListOfNUnsigneds =
+  __make_integer_seq<ListOfNUnsignedsImpl, unsigned, N>;
+
+template<typename T> struct TypeWrapper {
+  template<unsigned> using AsTemplate = T;
+};
+
+template<typename ...N> struct Splitter {
+  template<template<N> class ...L,
+           template<unsigned> class ...R> struct Split {
+    using Left = TypeList<L<0>...>;
+    using Right = TypeList<R<0>...>;
+  };
+};
+}
+
+template<typename TypeList, unsigned N, typename = detail::ListOfNUnsigneds<N>>
+struct SplitAtIndex;
+
+template<typename ...T, unsigned N, typename ...NUnsigneds>
+struct SplitAtIndex<TypeList<T...>, N, TypeList<NUnsigneds...>> :
+  detail::Splitter<NUnsigneds...>::
+    template Split<detail::TypeWrapper<T>::template AsTemplate...> {};
+
+template<typename T, int N> struct Rep : Rep<typename Rep<T, N-1>::type, 1> {};
+template<typename ...T> struct Rep<TypeList<T...>, 1> { typedef TypeList<T..., T...> type; };
+
+using Ints = Rep<TypeList<int>, 14>::type;
+
+template<typename T> extern int Size;
+template<typename ...T> constexpr int Size<TypeList<T...>> = sizeof...(T);
+
+using Left = SplitAtIndex<Ints, Size<Ints> / 2>::Left;
+using Right = SplitAtIndex<Ints, Size<Ints> / 2>::Right;
+static_assert(Size<Left> == 8192);
+static_assert(Size<Right> == 8192);
+
+template<typename L, typename R> struct Concat;
+template<typename ...L, typename ...R> struct Concat<TypeList<L...>, TypeList<R...>> {
+  using type = TypeList<L..., R...>;
+};
+
+using Ints = Concat<Left, Right>::type;