diff --git a/Eigen/src/Core/arch/GPU/Tuple.h b/Eigen/src/Core/arch/GPU/Tuple.h
index bbcdf64ff..97c54e5b0 100644
--- a/Eigen/src/Core/arch/GPU/Tuple.h
+++ b/Eigen/src/Core/arch/GPU/Tuple.h
@@ -165,8 +165,8 @@ struct tuple_cat_impl<NTuples, TupleImpl<N1, Args1...>, TupleImpl<N2, Args2...>,
   // then recursively calls again.
   template<typename Tuple1, size_t... I1s, typename Tuple2, size_t... I2s, typename... MoreTuples>
   static EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
-  ReturnType run(Tuple1&& tuple1, index_sequence<I1s...>,
-                 Tuple2&& tuple2, index_sequence<I2s...>,
+  ReturnType run(Tuple1&& tuple1, std::index_sequence<I1s...>,
+                 Tuple2&& tuple2, std::index_sequence<I2s...>,
                  MoreTuples&&... tuples) {
     return tuple_cat_impl<NTuples-1, MergedTupleType, Tuples...>::run(
         MergedTupleType(tuple_get_impl<I1s, Args1...>::run(std::forward<Tuple1>(tuple1))...,
@@ -178,8 +178,8 @@ struct tuple_cat_impl<NTuples, TupleImpl<N1, Args1...>, TupleImpl<N2, Args2...>,
   template<typename Tuple1, typename Tuple2, typename... MoreTuples>
   static EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   ReturnType run(Tuple1&& tuple1, Tuple2&& tuple2, MoreTuples&&... tuples) {
-    return run(std::forward<Tuple1>(tuple1), make_index_sequence<N1>{},
-               std::forward<Tuple2>(tuple2), make_index_sequence<N2>{},
+    return run(std::forward<Tuple1>(tuple1), std::make_index_sequence<N1>{},
+               std::forward<Tuple2>(tuple2), std::make_index_sequence<N2>{},
                std::forward<MoreTuples>(tuples)...);
   }
 };
diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index 62566eec9..fe7386c23 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -681,16 +681,6 @@
 #endif
 #endif
 
-// Does the compiler support result_of?
-// result_of was deprecated in c++17 and removed in c++ 20
-#ifndef EIGEN_HAS_STD_RESULT_OF
-#if EIGEN_COMP_CXXVER < 17
-#define EIGEN_HAS_STD_RESULT_OF 1
-#else
-#define EIGEN_HAS_STD_RESULT_OF 0
-#endif
-#endif
-
 // Does the compiler support std::hash?
 #ifndef EIGEN_HAS_STD_HASH
 // The std::hash struct is defined in C++11 but is not labelled as a __device__
@@ -710,28 +700,7 @@
 #endif
 #endif
 
-// Does the compiler fully support const expressions? (as in c++14)
-#ifndef EIGEN_HAS_CONSTEXPR
-  #if defined(EIGEN_CUDACC)
-  // Const expressions are supported provided that c++11 is enabled and we're using either clang or nvcc 7.5 or above
-    #if (EIGEN_COMP_CLANG || EIGEN_COMP_NVCC >= 70500)
-      #define EIGEN_HAS_CONSTEXPR 1
-    #endif
-  #else
-    #define EIGEN_HAS_CONSTEXPR 1
-  #endif
-
-  #ifndef EIGEN_HAS_CONSTEXPR
-    #define EIGEN_HAS_CONSTEXPR 0
-  #endif
-
-#endif // EIGEN_HAS_CONSTEXPR
-
-#if EIGEN_HAS_CONSTEXPR
 #define EIGEN_CONSTEXPR constexpr
-#else
-#define EIGEN_CONSTEXPR
-#endif
 
 // Does the compiler support C++11 math?
 // Let's be conservative and enable the default C++11 implementation only if we are sure it exists
@@ -760,7 +729,7 @@
 #endif
 #endif
 
-#if defined(EIGEN_CUDACC) && EIGEN_HAS_CONSTEXPR
+#if defined(EIGEN_CUDACC)
   // While available already with c++11, this is useful mostly starting with c++14 and relaxed constexpr rules
   #if defined(__NVCC__)
     // nvcc considers constexpr functions as __host__ __device__ with the option --expt-relaxed-constexpr
diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index 39b87edf3..67ec8c939 100755
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -243,17 +243,12 @@ EIGEN_CONSTEXPR auto index_list_size(T&& x) {
 /** \internal
   * Convenient struct to get the result type of a nullary, unary, binary, or
   * ternary functor.
-  * 
-  * Pre C++11:
-  * Supports both a Func::result_type member and templated
-  * Func::result<Func(ArgTypes...)>::type member.
-  * 
-  * If none of these members is provided, then the type of the first
-  * argument is returned.
-  * 
-  * Post C++11:
+  *
+  * Pre C++17:
   * This uses std::result_of. However, note the `type` member removes
   * const and converts references/pointers to their corresponding value type.
+  *
+  * Post C++17: Uses std::invoke_result
   */
 #if EIGEN_HAS_STD_INVOKE_RESULT
 template<typename T> struct result_of;
@@ -263,179 +258,34 @@ struct result_of<F(ArgTypes...)> {
   typedef typename std::invoke_result<F, ArgTypes...>::type type1;
   typedef typename remove_all<type1>::type type;
 };
-#elif EIGEN_HAS_STD_RESULT_OF
-template<typename T> struct result_of {
-  typedef typename std::result_of<T>::type type1;
-  typedef typename remove_all<type1>::type type;
-};
-#else
-template<typename T> struct result_of { };
 
-struct has_none {int a[1];};
-struct has_std_result_type {int a[2];};
-struct has_tr1_result {int a[3];};
-
-template<typename Func, int SizeOf>
-struct nullary_result_of_select {};
-
-template<typename Func>
-struct nullary_result_of_select<Func, sizeof(has_std_result_type)> {typedef typename Func::result_type type;};
-
-template<typename Func>
-struct nullary_result_of_select<Func, sizeof(has_tr1_result)> {typedef typename Func::template result<Func()>::type type;};
-
-template<typename Func>
-struct result_of<Func()> {
-    template<typename T>
-    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
-    template<typename T>
-    static has_tr1_result         testFunctor(T const *, typename T::template result<T()>::type const * = 0);
-    static has_none               testFunctor(...);
-
-    // note that the following indirection is needed for gcc-3.3
-    enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
-    typedef typename nullary_result_of_select<Func, FunctorType>::type type;
-};
-
-template<typename Func, typename ArgType, int SizeOf=sizeof(has_none)>
-struct unary_result_of_select {typedef typename internal::remove_all<ArgType>::type type;};
-
-template<typename Func, typename ArgType>
-struct unary_result_of_select<Func, ArgType, sizeof(has_std_result_type)> {typedef typename Func::result_type type;};
-
-template<typename Func, typename ArgType>
-struct unary_result_of_select<Func, ArgType, sizeof(has_tr1_result)> {typedef typename Func::template result<Func(ArgType)>::type type;};
-
-template<typename Func, typename ArgType>
-struct result_of<Func(ArgType)> {
-    template<typename T>
-    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
-    template<typename T>
-    static has_tr1_result         testFunctor(T const *, typename T::template result<T(ArgType)>::type const * = 0);
-    static has_none               testFunctor(...);
-
-    // note that the following indirection is needed for gcc-3.3
-    enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
-    typedef typename unary_result_of_select<Func, ArgType, FunctorType>::type type;
-};
-
-template<typename Func, typename ArgType0, typename ArgType1, int SizeOf=sizeof(has_none)>
-struct binary_result_of_select {typedef typename internal::remove_all<ArgType0>::type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1>
-struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_std_result_type)>
-{typedef typename Func::result_type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1>
-struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_tr1_result)>
-{typedef typename Func::template result<Func(ArgType0,ArgType1)>::type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1>
-struct result_of<Func(ArgType0,ArgType1)> {
-    template<typename T>
-    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
-    template<typename T>
-    static has_tr1_result         testFunctor(T const *, typename T::template result<T(ArgType0,ArgType1)>::type const * = 0);
-    static has_none               testFunctor(...);
-
-    // note that the following indirection is needed for gcc-3.3
-    enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
-    typedef typename binary_result_of_select<Func, ArgType0, ArgType1, FunctorType>::type type;
-};
-
-template<typename Func, typename ArgType0, typename ArgType1, typename ArgType2, int SizeOf=sizeof(has_none)>
-struct ternary_result_of_select {typedef typename internal::remove_all<ArgType0>::type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1, typename ArgType2>
-struct ternary_result_of_select<Func, ArgType0, ArgType1, ArgType2, sizeof(has_std_result_type)>
-{typedef typename Func::result_type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1, typename ArgType2>
-struct ternary_result_of_select<Func, ArgType0, ArgType1, ArgType2, sizeof(has_tr1_result)>
-{typedef typename Func::template result<Func(ArgType0,ArgType1,ArgType2)>::type type;};
-
-template<typename Func, typename ArgType0, typename ArgType1, typename ArgType2>
-struct result_of<Func(ArgType0,ArgType1,ArgType2)> {
-    template<typename T>
-    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
-    template<typename T>
-    static has_tr1_result         testFunctor(T const *, typename T::template result<T(ArgType0,ArgType1,ArgType2)>::type const * = 0);
-    static has_none               testFunctor(...);
-
-    // note that the following indirection is needed for gcc-3.3
-    enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
-    typedef typename ternary_result_of_select<Func, ArgType0, ArgType1, ArgType2, FunctorType>::type type;
-};
-
-#endif
-
-#if EIGEN_HAS_STD_INVOKE_RESULT
 template<typename F, typename... ArgTypes>
 struct invoke_result {
   typedef typename std::invoke_result<F, ArgTypes...>::type type1;
   typedef typename remove_all<type1>::type type;
 };
 #else
-template<typename F, typename... ArgTypes>
-struct invoke_result {
-  typedef typename result_of<F(ArgTypes...)>::type type1;
+template<typename T> struct result_of {
+  typedef typename std::result_of<T>::type type1;
   typedef typename remove_all<type1>::type type;
 };
-#endif
 
-// C++14 integer/index_sequence.
-#if defined(__cpp_lib_integer_sequence) && __cpp_lib_integer_sequence >= 201304L
-
-using std::integer_sequence;
-using std::make_integer_sequence;
-
-using std::index_sequence;
-using std::make_index_sequence;
-
-#else 
-
-template <typename T, T... Ints>
-struct integer_sequence {
-  static EIGEN_CONSTEXPR size_t size() EIGEN_NOEXCEPT { return sizeof...(Ints); }
+template<typename F, typename... ArgTypes>
+struct invoke_result {
+    typedef typename result_of<F(ArgTypes...)>::type type1;
+    typedef typename remove_all<type1>::type type;
 };
-
-template <typename T, typename Sequence, T N>
-struct append_integer;
-
-template<typename T, T... Ints, T N>
-struct append_integer<T, integer_sequence<T, Ints...>, N> {
-  using type = integer_sequence<T, Ints..., N>;
-};
-
-template<typename T, size_t N>
-struct generate_integer_sequence {
-  using type = typename append_integer<T, typename generate_integer_sequence<T, N-1>::type, N-1>::type;
-};
-
-template<typename T>
-struct generate_integer_sequence<T, 0> {
-  using type = integer_sequence<T>;
-};
-
-template <typename T, size_t N>
-using make_integer_sequence = typename generate_integer_sequence<T, N>::type;
-
-template<size_t... Ints>
-using index_sequence = integer_sequence<size_t, Ints...>;
-
-template<size_t N>
-using make_index_sequence = make_integer_sequence<size_t, N>;
-
 #endif
 
 // Reduces a sequence of bools to true if all are true, false otherwise.
 template<bool... values>
-using reduce_all = std::is_same<integer_sequence<bool, values..., true>, integer_sequence<bool, true, values...> >;
+using reduce_all = std::is_same<std::integer_sequence<bool, values..., true>,
+    std::integer_sequence<bool, true, values...> >;
 
 // Reduces a sequence of bools to true if any are true, false if all false.
 template<bool... values>
 using reduce_any = std::integral_constant<bool,
-    !std::is_same<integer_sequence<bool, values..., false>, integer_sequence<bool, false, values...> >::value>;
+    !std::is_same<std::integer_sequence<bool, values..., false>, std::integer_sequence<bool, false, values...> >::value>;
 
 struct meta_yes { char a[1]; };
 struct meta_no  { char a[2]; };
diff --git a/bench/tensors/tensor_benchmarks.h b/bench/tensors/tensor_benchmarks.h
index 0e8339e15..1a7a0fef5 100644
--- a/bench/tensors/tensor_benchmarks.h
+++ b/bench/tensors/tensor_benchmarks.h
@@ -219,14 +219,8 @@ template <typename Device, typename T> class BenchmarkSuite {
     size_b[1] = m_;
     TensorMap<Tensor<T, 2>, Eigen::Aligned> B(b_, size_b);
 
-#if defined(EIGEN_HAS_INDEX_LIST)
     Eigen::IndexPairList<Eigen::type2indexpair<0, 0>,
                          Eigen::type2indexpair<2, 1> > paddings;
-#else
-    Eigen::array<Eigen::IndexPair<TensorIndex>, 2> paddings;
-    paddings[0] = Eigen::IndexPair<TensorIndex>(0, 0);
-    paddings[1] = Eigen::IndexPair<TensorIndex>(2, 1);
-#endif
 #ifdef EIGEN_USE_SYCL // warmup for sycl
     for (int iter = 0; iter < 10; ++iter) {
       B.device(device_) = A.pad(paddings);
@@ -251,15 +245,7 @@ template <typename Device, typename T> class BenchmarkSuite {
     size_b[1] = k_/2;
     TensorMap<Tensor<T, 2>, Eigen::Aligned> B(b_, size_b);
 
-#ifndef EIGEN_HAS_INDEX_LIST
-    Eigen::array<TensorIndex, 2> strides;
-    strides[0] = 1;
-    strides[1] = 2;
-#else
-    // Take advantage of cxx11 to give the compiler information it can use to
-    // optimize the code.
     Eigen::IndexList<Eigen::type2index<1>, Eigen::type2index<2> > strides;
-#endif
 
 #ifdef EIGEN_USE_SYCL // warmup for sycl
     for (int iter = 0; iter < 10; ++iter) {
@@ -284,17 +270,8 @@ template <typename Device, typename T> class BenchmarkSuite {
     size_c[0] = m_;
     size_c[1] = n_;
     TensorMap<Tensor<T, 2>, Eigen::Aligned> C(c_, size_c);
-
-#ifndef EIGEN_HAS_INDEX_LIST
-    Eigen::array<int, 2> broadcast;
-    broadcast[0] = 1;
-    broadcast[1] = n_;
-#else
-    // Take advantage of cxx11 to give the compiler information it can use to
-    // optimize the code.
     Eigen::IndexList<Eigen::type2index<1>, int> broadcast;
     broadcast.set(1, n_);
-#endif
 
 #ifdef EIGEN_USE_SYCL // warmup for sycl
     for (int iter = 0; iter < 10; ++iter) {
@@ -385,15 +362,7 @@ for (int iter = 0; iter < 10; ++iter) {
     Eigen::array<TensorIndex, 1> output_size;
     output_size[0] = n_;
     TensorMap<Tensor<T, 1, 0, TensorIndex>, Eigen::Aligned> C(c_, output_size);
-
-#ifndef EIGEN_HAS_INDEX_LIST
-    Eigen::array<TensorIndex, 1> sum_along_dim;
-    sum_along_dim[0] = 0;
-#else
-    // Take advantage of cxx11 to give the compiler information it can use to
-    // optimize the code.
     Eigen::IndexList<Eigen::type2index<0>> sum_along_dim;
-#endif
 #ifdef EIGEN_USE_SYCL // warmup for sycl
   for (int iter = 0; iter < 10; ++iter) {
     C.device(device_) = B.sum(sum_along_dim);
diff --git a/doc/PreprocessorDirectives.dox b/doc/PreprocessorDirectives.dox
index 5a98539ee..4d232878e 100644
--- a/doc/PreprocessorDirectives.dox
+++ b/doc/PreprocessorDirectives.dox
@@ -65,7 +65,6 @@ functions by defining EIGEN_HAS_C99_MATH=1.
  - \b EIGEN_HAS_C99_MATH - controls the usage of C99 math functions such as erf, erfc, lgamma, etc.
  - \b EIGEN_HAS_CXX11_MATH - controls the implementation of some functions such as round, logp1, isinf, isnan, etc.
  - \b EIGEN_HAS_STD_RESULT_OF - defines whether std::result_of is supported
- - \b EIGEN_HAS_CONSTEXPR - defines whether relaxed const expression are supported
  - \b EIGEN_NO_IO - Disables any usage and support for `<iostreams>`.
 
 \section TopicPreprocessorDirectivesAssertions Assertions
diff --git a/test/gpu_test_helper.h b/test/gpu_test_helper.h
index d7649f93b..2c5a46b18 100644
--- a/test/gpu_test_helper.h
+++ b/test/gpu_test_helper.h
@@ -59,7 +59,7 @@ struct extract_output_indices_helper;
  * \tparam Ts the remaining types.
  */
 template<size_t N, size_t Idx, size_t... OutputIndices, typename T1, typename... Ts>
-struct extract_output_indices_helper<N, Idx, index_sequence<OutputIndices...>, T1, Ts...> {
+struct extract_output_indices_helper<N, Idx, std::index_sequence<OutputIndices...>, T1, Ts...> {
   using type = typename
     extract_output_indices_helper<
       N - 1, Idx + 1,
@@ -67,21 +67,21 @@ struct extract_output_indices_helper<N, Idx, index_sequence<OutputIndices...>, T
         // If is a non-const l-value reference, append index.
         std::is_lvalue_reference<T1>::value 
           && !std::is_const<typename std::remove_reference<T1>::type>::value,
-        index_sequence<OutputIndices..., Idx>,
-        index_sequence<OutputIndices...> >::type,
+        std::index_sequence<OutputIndices..., Idx>,
+        std::index_sequence<OutputIndices...> >::type,
       Ts...>::type;
 };
 
 // Base case.
 template<size_t Idx, size_t... OutputIndices>
-struct extract_output_indices_helper<0, Idx, index_sequence<OutputIndices...> > {
-  using type = index_sequence<OutputIndices...>;
+struct extract_output_indices_helper<0, Idx, std::index_sequence<OutputIndices...> > {
+  using type = std::index_sequence<OutputIndices...>;
 };
 
 // Extracts a set of indices into Types... that correspond to non-const
 // l-value references.
 template<typename... Types>
-using extract_output_indices = typename extract_output_indices_helper<sizeof...(Types), 0, index_sequence<>, Types...>::type;
+using extract_output_indices = typename extract_output_indices_helper<sizeof...(Types), 0, std::index_sequence<>, Types...>::type;
 
 // Helper struct for dealing with Generic functors that may return void.
 struct void_helper {
@@ -134,7 +134,7 @@ struct void_helper {
 // output_buffer_size is populated.
 template<typename Kernel, typename... Args, size_t... Indices, size_t... OutputIndices>
 EIGEN_DEVICE_FUNC
-void run_serialized(index_sequence<Indices...>, index_sequence<OutputIndices...>,
+void run_serialized(std::index_sequence<Indices...>, std::index_sequence<OutputIndices...>,
                     Kernel kernel, uint8_t* buffer, size_t capacity) {
   using test_detail::get;
   using test_detail::make_tuple;
@@ -175,7 +175,7 @@ void run_serialized(index_sequence<Indices...>, index_sequence<OutputIndices...>
 template<typename Kernel, typename... Args>
 EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 void run_serialized(Kernel kernel, uint8_t* buffer, size_t capacity) {
-  run_serialized<Kernel, Args...> (make_index_sequence<sizeof...(Args)>{},
+  run_serialized<Kernel, Args...> (std::make_index_sequence<sizeof...(Args)>{},
                                    extract_output_indices<Args...>{},
                                    kernel, buffer, capacity);
 }
@@ -206,8 +206,8 @@ void run_serialized_on_gpu_meta_kernel(const Kernel kernel, uint8_t* buffer, siz
 // buffer is not large enough to hold the outputs.
 template<typename Kernel, typename... Args, size_t... Indices, size_t... OutputIndices>
 auto run_serialized_on_gpu(size_t buffer_capacity_hint,
-                           index_sequence<Indices...>, 
-                           index_sequence<OutputIndices...>,
+                           std::index_sequence<Indices...>,
+                           std::index_sequence<OutputIndices...>,
                            Kernel kernel, Args&&... args) -> decltype(kernel(args...)) {  
   // Compute the required serialization buffer capacity.
   // Round up input size to next power of two to give a little extra room
@@ -323,7 +323,7 @@ template<typename Kernel, typename... Args>
 auto run_on_gpu(Kernel kernel, Args&&... args) -> decltype(kernel(args...)){  
   return internal::run_serialized_on_gpu<Kernel, Args...>(
       /*buffer_capacity_hint=*/ 0,
-      internal::make_index_sequence<sizeof...(Args)>{},
+      std::make_index_sequence<sizeof...(Args)>{},
       internal::extract_output_indices<Args...>{},
       kernel, std::forward<Args>(args)...);
 }
@@ -347,7 +347,7 @@ auto run_on_gpu_with_hint(size_t buffer_capacity_hint,
     Kernel kernel, Args&&... args) -> decltype(kernel(args...)){  
   return internal::run_serialized_on_gpu<Kernel, Args...>(
       buffer_capacity_hint,
-      internal::make_index_sequence<sizeof...(Args)>{},
+      std::make_index_sequence<sizeof...(Args)>{},
       internal::extract_output_indices<Args...>{},
       kernel, std::forward<Args>(args)...);
 }
diff --git a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
index 6a4124519..b57b14c8d 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
@@ -388,7 +388,6 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
       // Nothing to do: rank 0 tensors have fixed size
     }
 
-#ifdef EIGEN_HAS_INDEX_LIST
     template <typename FirstType, typename... OtherTypes>
     EIGEN_DEVICE_FUNC
     void resize(const Eigen::IndexList<FirstType, OtherTypes...>& dimensions) {
@@ -398,7 +397,6 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
       }
       resize(dims);
     }
-#endif
 
     /** Custom Dimension */
     template<typename CustomDimension,
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensionList.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensionList.h
index ed827c1f8..c58838e65 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensionList.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensionList.h
@@ -45,8 +45,6 @@ template<DenseIndex n, typename Index, std::size_t Rank> const Index array_get(c
   return n;
 }
 
-
-#if EIGEN_HAS_CONSTEXPR
 template <typename Index, std::size_t Rank>
 struct index_known_statically_impl<DimensionList<Index, Rank> > {
   EIGEN_DEVICE_FUNC static constexpr bool run(const DenseIndex) {
@@ -138,99 +136,6 @@ struct index_statically_lt_impl<const DimensionList<Index, Rank> > {
   }
 };
 
-#else
-template <typename Index, std::size_t Rank>
-struct index_known_statically_impl<DimensionList<Index, Rank> > {
-  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE bool run(const DenseIndex) {
-    return true;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct index_known_statically_impl<const DimensionList<Index, Rank> > {
-  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE bool run(const DenseIndex) {
-    return true;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct all_indices_known_statically_impl<DimensionList<Index, Rank> > {
-  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE bool run() {
-    return true;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct all_indices_known_statically_impl<const DimensionList<Index, Rank> > {
-  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE bool run() {
-    return true;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct indices_statically_known_to_increase_impl<DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run() {
-    return true;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct indices_statically_known_to_increase_impl<const DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run() {
-    return true;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct index_statically_eq_impl<DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct index_statically_eq_impl<const DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct index_statically_ne_impl<DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex){
-    return false;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct index_statically_ne_impl<const DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct index_statically_gt_impl<DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct index_statically_gt_impl<const DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-
-template <typename Index, std::size_t Rank>
-struct index_statically_lt_impl<DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-template <typename Index, std::size_t Rank>
-struct index_statically_lt_impl<const DimensionList<Index, Rank> > {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const DenseIndex, const DenseIndex) {
-    return false;
-  }
-};
-#endif
-
 }  // end namespace internal
 }  // end namespace Eigen
 
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
index 84ae848e1..d44ab4c5b 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
@@ -297,7 +297,6 @@ struct DSizes : array<DenseIndex, NumDims> {
     }
   }
 
-#ifdef EIGEN_HAS_INDEX_LIST
   template <typename FirstType, typename... OtherTypes>
   EIGEN_DEVICE_FUNC
   explicit DSizes(const Eigen::IndexList<FirstType, OtherTypes...>& dimensions) {
@@ -305,7 +304,6 @@ struct DSizes : array<DenseIndex, NumDims> {
       (*this)[i] = dimensions[i];
     }
   }
-#endif
 
 #ifndef EIGEN_EMULATE_CXX11_META_H
   template <typename std::ptrdiff_t... Indices>
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h b/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
index e5030e965..0e9c7e59c 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
@@ -12,10 +12,6 @@
 
 #include "./InternalHeaderCheck.h"
 
-#if EIGEN_HAS_CONSTEXPR
-
-#define EIGEN_HAS_INDEX_LIST
-
 namespace Eigen {
 
 /** \internal
@@ -609,81 +605,6 @@ struct index_pair_second_statically_eq_impl<const IndexPairList<FirstType, Other
 }  // end namespace internal
 }  // end namespace Eigen
 
-#else
-
-namespace Eigen {
-namespace internal {
-
-template <typename T>
-struct index_known_statically_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(const Index) {
-    return false;
-  }
-};
-
-template <typename T>
-struct all_indices_known_statically_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run() {
-    return false;
-  }
-};
-
-template <typename T>
-struct indices_statically_known_to_increase_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run() {
-    return false;
-  }
-};
-
-template <typename T>
-struct index_statically_eq_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-template <typename T>
-struct index_statically_ne_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-template <typename T>
-struct index_statically_gt_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-template <typename T>
-struct index_statically_lt_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-template <typename Tx>
-struct index_pair_first_statically_eq_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-template <typename Tx>
-struct index_pair_second_statically_eq_impl {
-  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool run(Index, Index) {
-    return false;
-  }
-};
-
-
-
-}  // end namespace internal
-}  // end namespace Eigen
-
-#endif
-
 
 namespace Eigen {
 namespace internal {
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h b/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
index ba79907ea..e4426fe9c 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
@@ -109,13 +109,9 @@ struct TensorEvaluator<const TensorReshapingOp<NewDimensions, ArgType>, Device>
 
   // clang-format off
   static const ReshapingKind kind =
-#if defined(EIGEN_HAS_INDEX_LIST)
         (NumOutputDims == 2 && internal::index_statically_eq<NewDimensions>(/*index=*/0, /*value=*/1)) ? OneByN
       : (NumOutputDims == 2 && internal::index_statically_eq<NewDimensions>(/*index=*/1, /*value=*/1)) ? NByOne
       : Runtime;
-#else
-        Runtime;
-#endif
   // clang-format on
 
   enum {
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorPadding.h b/unsupported/Eigen/CXX11/src/Tensor/TensorPadding.h
index a9706dac8..d111d80a3 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorPadding.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorPadding.h
@@ -512,35 +512,20 @@ struct TensorEvaluator<const TensorPaddingOp<PaddingDimensions, ArgType>, Device
 
   EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool isPaddingAtIndexForDim(
       Index index, int dim_index) const {
-#if defined(EIGEN_HAS_INDEX_LIST)
     return (!internal::index_pair_first_statically_eq<PaddingDimensions>(dim_index, 0) &&
             index < m_padding[dim_index].first) ||
         (!internal::index_pair_second_statically_eq<PaddingDimensions>(dim_index, 0) &&
          index >= m_dimensions[dim_index] - m_padding[dim_index].second);
-#else
-    return (index < m_padding[dim_index].first) ||
-           (index >= m_dimensions[dim_index] - m_padding[dim_index].second);
-#endif
   }
 
   EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool isLeftPaddingCompileTimeZero(
       int dim_index) const {
-#if defined(EIGEN_HAS_INDEX_LIST)
     return internal::index_pair_first_statically_eq<PaddingDimensions>(dim_index, 0);
-#else
-    EIGEN_UNUSED_VARIABLE(dim_index);
-    return false;
-#endif
   }
 
   EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool isRightPaddingCompileTimeZero(
       int dim_index) const {
-#if defined(EIGEN_HAS_INDEX_LIST)
     return internal::index_pair_second_statically_eq<PaddingDimensions>(dim_index, 0);
-#else
-    EIGEN_UNUSED_VARIABLE(dim_index);
-    return false;
-#endif
   }
 
 
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h b/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
index 034252874..8bbe49edc 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
@@ -108,7 +108,6 @@ struct preserve_inner_most_dims {
   static const bool value = false;
 };
 
-#if EIGEN_HAS_CONSTEXPR
 template <typename ReducedDims, int NumTensorDims>
 struct are_inner_most_dims<ReducedDims, NumTensorDims, ColMajor>{
   static const bool tmp1 = indices_statically_known_to_increase<ReducedDims>();
@@ -137,7 +136,6 @@ struct preserve_inner_most_dims<ReducedDims, NumTensorDims, RowMajor>{
   static const bool tmp2 = index_statically_lt<ReducedDims>(array_size<ReducedDims>::value - 1, NumTensorDims - 1);
   static const bool value = tmp1 & tmp2;
 };
-#endif
 
 
 template <int DimIndex, typename Self, typename Op>
diff --git a/unsupported/test/cxx11_tensor_argmax_sycl.cpp b/unsupported/test/cxx11_tensor_argmax_sycl.cpp
index 7ac71286e..41ea3cf7b 100644
--- a/unsupported/test/cxx11_tensor_argmax_sycl.cpp
+++ b/unsupported/test/cxx11_tensor_argmax_sycl.cpp
@@ -16,7 +16,6 @@
 
 #define EIGEN_DEFAULT_DENSE_INDEX_TYPE int64_t
 #define EIGEN_USE_SYCL
-#define EIGEN_HAS_CONSTEXPR 1
 
 #include "main.h"
 
diff --git a/unsupported/test/cxx11_tensor_broadcasting.cpp b/unsupported/test/cxx11_tensor_broadcasting.cpp
index 1523657de..2da35e4af 100644
--- a/unsupported/test/cxx11_tensor_broadcasting.cpp
+++ b/unsupported/test/cxx11_tensor_broadcasting.cpp
@@ -116,15 +116,7 @@ static void test_static_broadcasting()
   Tensor<float, 3, DataLayout> tensor(8,3,5);
   tensor.setRandom();
 
-#if defined(EIGEN_HAS_INDEX_LIST)
   Eigen::IndexList<Eigen::type2index<2>, Eigen::type2index<3>, Eigen::type2index<4>> broadcasts;
-#else
-  Eigen::array<int, 3> broadcasts;
-  broadcasts[0] = 2;
-  broadcasts[1] = 3;
-  broadcasts[2] = 4;
-#endif
-
   Tensor<float, 3, DataLayout> broadcast;
   broadcast = tensor.broadcast(broadcasts);
 
diff --git a/unsupported/test/cxx11_tensor_index_list.cpp b/unsupported/test/cxx11_tensor_index_list.cpp
index 2166532c8..e8e101f3d 100644
--- a/unsupported/test/cxx11_tensor_index_list.cpp
+++ b/unsupported/test/cxx11_tensor_index_list.cpp
@@ -11,8 +11,6 @@
 
 #include <Eigen/CXX11/Tensor>
 
-#ifdef EIGEN_HAS_INDEX_LIST
-
 static void test_static_index_list()
 {
   Tensor<float, 4> tensor(2,3,5,7);
@@ -370,16 +368,12 @@ static void test_dim_check()
 }
 
 
-#endif
-
 EIGEN_DECLARE_TEST(cxx11_tensor_index_list)
 {
-#ifdef EIGEN_HAS_INDEX_LIST
   CALL_SUBTEST(test_static_index_list());
   CALL_SUBTEST(test_type2index_list());
   CALL_SUBTEST(test_type2indexpair_list());
   CALL_SUBTEST(test_dynamic_index_list());
   CALL_SUBTEST(test_mixed_index_list());
   CALL_SUBTEST(test_dim_check());
-#endif
 }
diff --git a/unsupported/test/cxx11_tensor_morphing.cpp b/unsupported/test/cxx11_tensor_morphing.cpp
index ed5d5ade3..d039a7e6b 100644
--- a/unsupported/test/cxx11_tensor_morphing.cpp
+++ b/unsupported/test/cxx11_tensor_morphing.cpp
@@ -43,7 +43,6 @@ static void test_simple_reshape()
 
 template <typename>
 static void test_static_reshape() {
-#if defined(EIGEN_HAS_INDEX_LIST)
   using Eigen::type2index;
 
   Tensor<float, 5> tensor(2, 3, 1, 7, 1);
@@ -60,7 +59,6 @@ static void test_static_reshape() {
       }
     }
   }
-#endif
 }
 
 template <typename>
diff --git a/unsupported/test/cxx11_tensor_reduction.cpp b/unsupported/test/cxx11_tensor_reduction.cpp
index 9648b9c8b..a090e4a8f 100644
--- a/unsupported/test/cxx11_tensor_reduction.cpp
+++ b/unsupported/test/cxx11_tensor_reduction.cpp
@@ -370,13 +370,7 @@ static void test_static_dims() {
   Tensor<float, 2, DataLayout> out(72, 97);
   in.setRandom();
 
-#if !EIGEN_HAS_CONSTEXPR
-  array<int, 2> reduction_axis;
-  reduction_axis[0] = 1;
-  reduction_axis[1] = 3;
-#else
   Eigen::IndexList<Eigen::type2index<1>, Eigen::type2index<3> > reduction_axis;
-#endif
 
   out = in.maximum(reduction_axis);
 
@@ -400,14 +394,8 @@ static void test_innermost_last_dims() {
   in.setRandom();
 
 // Reduce on the innermost dimensions.
-#if !EIGEN_HAS_CONSTEXPR
-  array<int, 2> reduction_axis;
-  reduction_axis[0] = 0;
-  reduction_axis[1] = 1;
-#else
   // This triggers the use of packets for ColMajor.
   Eigen::IndexList<Eigen::type2index<0>, Eigen::type2index<1> > reduction_axis;
-#endif
 
   out = in.maximum(reduction_axis);
 
@@ -431,14 +419,8 @@ static void test_innermost_first_dims() {
   in.setRandom();
 
 // Reduce on the innermost dimensions.
-#if !EIGEN_HAS_CONSTEXPR
-  array<int, 2> reduction_axis;
-  reduction_axis[0] = 2;
-  reduction_axis[1] = 3;
-#else
   // This triggers the use of packets for RowMajor.
   Eigen::IndexList<Eigen::type2index<2>, Eigen::type2index<3>> reduction_axis;
-#endif
 
   out = in.maximum(reduction_axis);
 
@@ -462,14 +444,8 @@ static void test_reduce_middle_dims() {
   in.setRandom();
 
 // Reduce on the innermost dimensions.
-#if !EIGEN_HAS_CONSTEXPR
-  array<int, 2> reduction_axis;
-  reduction_axis[0] = 1;
-  reduction_axis[1] = 2;
-#else
   // This triggers the use of packets for RowMajor.
   Eigen::IndexList<Eigen::type2index<1>, Eigen::type2index<2>> reduction_axis;
-#endif
 
   out = in.maximum(reduction_axis);
 
diff --git a/unsupported/test/cxx11_tensor_reduction_sycl.cpp b/unsupported/test/cxx11_tensor_reduction_sycl.cpp
index a297716e4..3afa62acf 100644
--- a/unsupported/test/cxx11_tensor_reduction_sycl.cpp
+++ b/unsupported/test/cxx11_tensor_reduction_sycl.cpp
@@ -16,7 +16,6 @@
 
 #define EIGEN_DEFAULT_DENSE_INDEX_TYPE int64_t
 #define EIGEN_USE_SYCL
-#define EIGEN_HAS_CONSTEXPR 1
 
 #include "main.h"