diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 746d5812fba0..0fe3ab44d246 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -914,10 +914,8 @@ set(files
   expected
   experimental/__config
   experimental/__memory
-  experimental/__simd/abi_tag.h
   experimental/__simd/aligned_tag.h
   experimental/__simd/declaration.h
-  experimental/__simd/internal_declaration.h
   experimental/__simd/reference.h
   experimental/__simd/scalar.h
   experimental/__simd/simd.h
diff --git a/libcxx/include/experimental/__simd/abi_tag.h b/libcxx/include/experimental/__simd/abi_tag.h
deleted file mode 100644
index cec5be65ce5c..000000000000
--- a/libcxx/include/experimental/__simd/abi_tag.h
+++ /dev/null
@@ -1,55 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_ABI_TAG_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_ABI_TAG_H
-
-#include <cstddef>
-#include <experimental/__config>
-#include <experimental/__simd/internal_declaration.h>
-
-#if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-
-_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
-inline namespace parallelism_v2 {
-namespace simd_abi {
-
-using scalar = __scalar;
-
-// TODO: make this platform dependent
-template <int _Np>
-using fixed_size = __vec_ext<_Np>;
-
-template <class _Tp>
-inline constexpr int max_fixed_size = 32;
-
-// TODO: make this platform dependent
-template <class _Tp>
-using compatible = __vec_ext<16 / sizeof(_Tp)>;
-
-// TODO: make this platform dependent
-template <class _Tp>
-using native = __vec_ext<_LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(_Tp)>;
-
-// TODO: make this platform dependent
-template <class _Tp, size_t _Np, class... _Abis>
-struct deduce {
-  using type = fixed_size<_Np>;
-};
-
-// TODO: make this platform dependent
-template <class _Tp, size_t _Np, class... _Abis>
-using deduce_t = typename deduce<_Tp, _Np, _Abis...>::type;
-
-} // namespace simd_abi
-} // namespace parallelism_v2
-_LIBCPP_END_NAMESPACE_EXPERIMENTAL
-
-#endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_ABI_TAG_H
diff --git a/libcxx/include/experimental/__simd/aligned_tag.h b/libcxx/include/experimental/__simd/aligned_tag.h
index d216a21c073f..edbb3b24931f 100644
--- a/libcxx/include/experimental/__simd/aligned_tag.h
+++ b/libcxx/include/experimental/__simd/aligned_tag.h
@@ -10,10 +10,10 @@
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_ALIGNED_TAG_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_ALIGNED_TAG_H
 
-#include <__bit/bit_ceil.h>
 #include <__memory/assume_aligned.h>
 #include <cstddef>
 #include <experimental/__config>
+#include <experimental/__simd/traits.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
@@ -30,9 +30,12 @@ struct element_aligned_tag {
   }
 };
 
+template <>
+inline constexpr bool is_simd_flag_type_v<element_aligned_tag> = true;
+
 struct vector_aligned_tag {
   template <class _Tp, class _Up = typename _Tp::value_type>
-  static constexpr size_t __alignment = std::__bit_ceil(sizeof(_Up) * _Tp::size());
+  static constexpr size_t __alignment = memory_alignment_v<_Tp, _Up>;
 
   template <class _Tp, class _Up>
   static _LIBCPP_HIDE_FROM_ABI constexpr _Up* __apply(_Up* __ptr) {
@@ -40,6 +43,9 @@ struct vector_aligned_tag {
   }
 };
 
+template <>
+inline constexpr bool is_simd_flag_type_v<vector_aligned_tag> = true;
+
 template <size_t _Np>
 struct overaligned_tag {
   template <class _Tp, class _Up = typename _Tp::value_type>
@@ -51,6 +57,9 @@ struct overaligned_tag {
   }
 };
 
+template <size_t _Np>
+inline constexpr bool is_simd_flag_type_v<overaligned_tag<_Np>> = true;
+
 inline constexpr element_aligned_tag element_aligned{};
 
 inline constexpr vector_aligned_tag vector_aligned{};
diff --git a/libcxx/include/experimental/__simd/declaration.h b/libcxx/include/experimental/__simd/declaration.h
index 065faeaec384..7b45d035c271 100644
--- a/libcxx/include/experimental/__simd/declaration.h
+++ b/libcxx/include/experimental/__simd/declaration.h
@@ -10,13 +10,63 @@
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
 
+#include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/abi_tag.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
+namespace simd_abi {
+template <int>
+struct __vec_ext;
+struct __scalar;
+
+using scalar = __scalar;
+
+// TODO: make this platform dependent
+template <int _Np>
+using fixed_size = __vec_ext<_Np>;
+
+template <class _Tp>
+inline constexpr int max_fixed_size = 32;
+
+// TODO: make this platform dependent
+template <class _Tp>
+using compatible = __vec_ext<16 / sizeof(_Tp)>;
+
+// TODO: make this platform dependent
+template <class _Tp>
+using native = __vec_ext<_LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(_Tp)>;
+
+// TODO: make this platform dependent
+template <class _Tp, size_t _Np, class... _Abis>
+struct deduce {
+  using type = fixed_size<_Np>;
+};
+
+// TODO: make this platform dependent
+template <class _Tp, size_t _Np, class... _Abis>
+using deduce_t = typename deduce<_Tp, _Np, _Abis...>::type;
+
+} // namespace simd_abi
+
+template <class _Tp, class _Abi>
+struct __simd_storage;
+
+template <class _Tp, class _Abi>
+struct __mask_storage;
+
+template <class _Tp, class _Abi>
+struct __simd_operations;
+
+template <class _Tp, class _Abi>
+struct __mask_operations;
+
+struct element_aligned_tag;
+struct vector_aligned_tag;
+template <size_t>
+struct overaligned_tag;
 
 template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
 class simd;
diff --git a/libcxx/include/experimental/__simd/internal_declaration.h b/libcxx/include/experimental/__simd/internal_declaration.h
deleted file mode 100644
index 9ad1ad1ae319..000000000000
--- a/libcxx/include/experimental/__simd/internal_declaration.h
+++ /dev/null
@@ -1,41 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_INTERNAL_DECLARATION_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_INTERNAL_DECLARATION_H
-
-#include <experimental/__config>
-
-#if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-
-_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
-inline namespace parallelism_v2 {
-namespace simd_abi {
-template <int>
-struct __vec_ext;
-struct __scalar;
-} // namespace simd_abi
-
-template <class _Tp, class _Abi>
-struct __simd_storage;
-
-template <class _Tp, class _Abi>
-struct __mask_storage;
-
-template <class _Tp, class _Abi>
-struct __simd_operations;
-
-template <class _Tp, class _Abi>
-struct __mask_operations;
-
-} // namespace parallelism_v2
-_LIBCPP_END_NAMESPACE_EXPERIMENTAL
-
-#endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_INTERNAL_DECLARATION_H
diff --git a/libcxx/include/experimental/__simd/scalar.h b/libcxx/include/experimental/__simd/scalar.h
index 53fa1c29f374..5eeff4c1e82a 100644
--- a/libcxx/include/experimental/__simd/scalar.h
+++ b/libcxx/include/experimental/__simd/scalar.h
@@ -12,7 +12,7 @@
 
 #include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/internal_declaration.h>
+#include <experimental/__simd/declaration.h>
 #include <experimental/__simd/traits.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
diff --git a/libcxx/include/experimental/__simd/simd.h b/libcxx/include/experimental/__simd/simd.h
index ffb328eb345b..c345811fee7f 100644
--- a/libcxx/include/experimental/__simd/simd.h
+++ b/libcxx/include/experimental/__simd/simd.h
@@ -15,9 +15,7 @@
 #include <__utility/forward.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/abi_tag.h>
 #include <experimental/__simd/declaration.h>
-#include <experimental/__simd/internal_declaration.h>
 #include <experimental/__simd/reference.h>
 #include <experimental/__simd/traits.h>
 #include <experimental/__simd/utility.h>
diff --git a/libcxx/include/experimental/__simd/simd_mask.h b/libcxx/include/experimental/__simd/simd_mask.h
index 325b8409e3b6..db03843b46e3 100644
--- a/libcxx/include/experimental/__simd/simd_mask.h
+++ b/libcxx/include/experimental/__simd/simd_mask.h
@@ -13,9 +13,7 @@
 #include <__type_traits/is_same.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/abi_tag.h>
 #include <experimental/__simd/declaration.h>
-#include <experimental/__simd/internal_declaration.h>
 #include <experimental/__simd/reference.h>
 #include <experimental/__simd/traits.h>
 
diff --git a/libcxx/include/experimental/__simd/traits.h b/libcxx/include/experimental/__simd/traits.h
index 9b4abe9d0c23..ec25b4bfa7f9 100644
--- a/libcxx/include/experimental/__simd/traits.h
+++ b/libcxx/include/experimental/__simd/traits.h
@@ -10,14 +10,12 @@
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H
 
+#include <__bit/bit_ceil.h>
 #include <__type_traits/integral_constant.h>
 #include <__type_traits/is_same.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/abi_tag.h>
-#include <experimental/__simd/aligned_tag.h>
 #include <experimental/__simd/declaration.h>
-#include <experimental/__simd/internal_declaration.h>
 #include <experimental/__simd/utility.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
@@ -47,15 +45,6 @@ struct is_simd_mask : bool_constant<is_simd_mask_v<_Tp>> {};
 template <class _Tp>
 inline constexpr bool is_simd_flag_type_v = false;
 
-template <>
-inline constexpr bool is_simd_flag_type_v<element_aligned_tag> = true;
-
-template <>
-inline constexpr bool is_simd_flag_type_v<vector_aligned_tag> = true;
-
-template <size_t _Np>
-inline constexpr bool is_simd_flag_type_v<overaligned_tag<_Np>> = true;
-
 template <class _Tp>
 struct is_simd_flag_type : bool_constant<is_simd_flag_type_v<_Tp>> {};
 
@@ -71,7 +60,7 @@ inline constexpr size_t simd_size_v = simd_size<_Tp, _Abi>::value;
 template <class _Tp,
           class _Up = typename _Tp::value_type,
           bool      = (is_simd_v<_Tp> && __is_vectorizable_v<_Up>) || (is_simd_mask_v<_Tp> && is_same_v<_Up, bool>)>
-struct memory_alignment : integral_constant<size_t, vector_aligned_tag::__alignment<_Tp, _Up>> {};
+struct memory_alignment : integral_constant<size_t, std::__bit_ceil(sizeof(_Up) * _Tp::size())> {};
 
 template <class _Tp, class _Up>
 struct memory_alignment<_Tp, _Up, false> {};
diff --git a/libcxx/include/experimental/__simd/vec_ext.h b/libcxx/include/experimental/__simd/vec_ext.h
index 56a0b888104b..07ba032f493b 100644
--- a/libcxx/include/experimental/__simd/vec_ext.h
+++ b/libcxx/include/experimental/__simd/vec_ext.h
@@ -15,7 +15,7 @@
 #include <__utility/integer_sequence.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <experimental/__simd/internal_declaration.h>
+#include <experimental/__simd/declaration.h>
 #include <experimental/__simd/traits.h>
 #include <experimental/__simd/utility.h>
 
diff --git a/libcxx/include/experimental/simd b/libcxx/include/experimental/simd
index 56858832857c..adca9faa47bb 100644
--- a/libcxx/include/experimental/simd
+++ b/libcxx/include/experimental/simd
@@ -78,7 +78,6 @@ inline namespace parallelism_v2 {
 #endif
 
 #include <experimental/__config>
-#include <experimental/__simd/abi_tag.h>
 #include <experimental/__simd/aligned_tag.h>
 #include <experimental/__simd/declaration.h>
 #include <experimental/__simd/scalar.h>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index a37e96205cf2..d10670d4faaf 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -530,10 +530,8 @@ module std_experimental [system] {
     export *
   }
   module simd {
-    module abi_tag              { private header "experimental/__simd/abi_tag.h" }
     module aligned_tag          { private header "experimental/__simd/aligned_tag.h" }
     module declaration          { private header "experimental/__simd/declaration.h" }
-    module internal_declaration { private header "experimental/__simd/internal_declaration.h" }
     module reference            { private header "experimental/__simd/reference.h" }
     module scalar               { private header "experimental/__simd/scalar.h" }
     module simd                 { private header "experimental/__simd/simd.h" }