[libc++] Remove <tuple> from <variant> (#83183)

This moves a utility from `<tuple>` into an implementation detail header and refactors the selection of the variant index type to use.
llvm · Mar 11, 2024 · 2a38551 · 2a38551
1 parent 2b8f1da
commit 2a38551
Show file tree

Hide file tree

Showing 14 changed files with 98 additions and 59 deletions.
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
@@ -701,6 +701,7 @@ set(files
   __thread/thread.h
   __thread/timed_backoff_policy.h
   __tree
+  __tuple/find_index.h
   __tuple/make_tuple_types.h
   __tuple/pair_like.h
   __tuple/sfinae_helpers.h

diff --git a/libcxx/include/__tuple/find_index.h b/libcxx/include/__tuple/find_index.h
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___TUPLE_FIND_INDEX_H
+#define _LIBCPP___TUPLE_FIND_INDEX_H
+
+#include <__config>
+#include <__type_traits/is_same.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 14
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __find_detail {
+
+static constexpr size_t __not_found = static_cast<size_t>(-1);
+static constexpr size_t __ambiguous = __not_found - 1;
+
+inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) {
+  return !__matches ? __res : (__res == __not_found ? __curr_i : __ambiguous);
+}
+
+template <size_t _Nx>
+inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
+  return __i == _Nx
+           ? __not_found
+           : __find_detail::__find_idx_return(__i, __find_detail::__find_idx(__i + 1, __matches), __matches[__i]);
+}
+
+template <class _T1, class... _Args>
+struct __find_exactly_one_checked {
+  static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...};
+  static constexpr size_t value                     = __find_detail::__find_idx(0, __matches);
+  static_assert(value != __not_found, "type not found in type list");
+  static_assert(value != __ambiguous, "type occurs more than once in type list");
+};
+
+template <class _T1>
+struct __find_exactly_one_checked<_T1> {
+  static_assert(!is_same<_T1, _T1>::value, "type not in empty type list");
+};
+
+} // namespace __find_detail
+
+template <typename _T1, typename... _Args>
+struct __find_exactly_one_t : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 14
+
+#endif // _LIBCPP___TUPLE_FIND_INDEX_H
diff --git a/libcxx/include/libcxx.imp b/libcxx/include/libcxx.imp
@@ -697,6 +697,7 @@
   { include: [ "<__thread/this_thread.h>", "private", "<thread>", "public" ] },
   { include: [ "<__thread/thread.h>", "private", "<thread>", "public" ] },
   { include: [ "<__thread/timed_backoff_policy.h>", "private", "<thread>", "public" ] },
+  { include: [ "<__tuple/find_index.h>", "private", "<tuple>", "public" ] },
   { include: [ "<__tuple/make_tuple_types.h>", "private", "<tuple>", "public" ] },
   { include: [ "<__tuple/pair_like.h>", "private", "<tuple>", "public" ] },
   { include: [ "<__tuple/sfinae_helpers.h>", "private", "<tuple>", "public" ] },

diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
@@ -1799,6 +1799,7 @@ module std_private_thread_thread               [system] {
 }
 module std_private_thread_timed_backoff_policy [system] { header "__thread/timed_backoff_policy.h" }
 
+module std_private_tuple_find_index       [system] { header "__tuple/find_index.h" }
 module std_private_tuple_make_tuple_types [system] { header "__tuple/make_tuple_types.h" }
 module std_private_tuple_pair_like        [system] {
   header "__tuple/pair_like.h"

diff --git a/libcxx/include/tuple b/libcxx/include/tuple
@@ -213,6 +213,7 @@ template <class... Types>
 #include <__fwd/tuple.h>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/uses_allocator.h>
+#include <__tuple/find_index.h>
 #include <__tuple/make_tuple_types.h>
 #include <__tuple/sfinae_helpers.h>
 #include <__tuple/tuple_element.h>
@@ -1087,40 +1088,6 @@ get(const tuple<_Tp...>&& __t) _NOEXCEPT {
 
 #  if _LIBCPP_STD_VER >= 14
 
-namespace __find_detail {
-
-static constexpr size_t __not_found = static_cast<size_t>(-1);
-static constexpr size_t __ambiguous = __not_found - 1;
-
-inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) {
-  return !__matches ? __res : (__res == __not_found ? __curr_i : __ambiguous);
-}
-
-template <size_t _Nx>
-inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
-  return __i == _Nx
-           ? __not_found
-           : __find_detail::__find_idx_return(__i, __find_detail::__find_idx(__i + 1, __matches), __matches[__i]);
-}
-
-template <class _T1, class... _Args>
-struct __find_exactly_one_checked {
-  static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...};
-  static constexpr size_t value                     = __find_detail::__find_idx(0, __matches);
-  static_assert(value != __not_found, "type not found in type list");
-  static_assert(value != __ambiguous, "type occurs more than once in type list");
-};
-
-template <class _T1>
-struct __find_exactly_one_checked<_T1> {
-  static_assert(!is_same<_T1, _T1>::value, "type not in empty type list");
-};
-
-} // namespace __find_detail
-
-template <typename _T1, typename... _Args>
-struct __find_exactly_one_t : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {};
-
 template <class _T1, class... _Args>
 inline _LIBCPP_HIDE_FROM_ABI constexpr _T1& get(tuple<_Args...>& __tup) noexcept {
   return std::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);

diff --git a/libcxx/include/variant b/libcxx/include/variant
@@ -221,13 +221,18 @@ namespace std {
 #include <__functional/operations.h>
 #include <__functional/unary_function.h>
 #include <__memory/addressof.h>
+#include <__tuple/find_index.h>
+#include <__tuple/sfinae_helpers.h>
 #include <__type_traits/add_const.h>
 #include <__type_traits/add_cv.h>
 #include <__type_traits/add_pointer.h>
 #include <__type_traits/add_volatile.h>
+#include <__type_traits/common_type.h>
 #include <__type_traits/dependent_type.h>
 #include <__type_traits/is_array.h>
+#include <__type_traits/is_default_constructible.h>
 #include <__type_traits/is_destructible.h>
+#include <__type_traits/is_nothrow_assignable.h>
 #include <__type_traits/is_nothrow_move_constructible.h>
 #include <__type_traits/is_trivially_copy_assignable.h>
 #include <__type_traits/is_trivially_copy_constructible.h>
@@ -242,14 +247,14 @@ namespace std {
 #include <__utility/forward.h>
 #include <__utility/forward_like.h>
 #include <__utility/in_place.h>
+#include <__utility/integer_sequence.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <__variant/monostate.h>
 #include <__verbose_abort>
 #include <initializer_list>
 #include <limits>
 #include <new>
-#include <tuple>
 #include <version>
 
 // standard-mandated includes
@@ -340,21 +345,20 @@ struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
 
 inline constexpr size_t variant_npos = static_cast<size_t>(-1);
 
-_LIBCPP_HIDE_FROM_ABI constexpr int __choose_index_type(unsigned int __num_elem) {
-  if (__num_elem < numeric_limits<unsigned char>::max())
-    return 0;
-  if (__num_elem < numeric_limits<unsigned short>::max())
-    return 1;
-  return 2;
+template <size_t _NumAlternatives>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __choose_index_type() {
+#ifdef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
+  if constexpr (_NumAlternatives < numeric_limits<unsigned char>::max())
+    return static_cast<unsigned char>(0);
+  else if constexpr (_NumAlternatives < numeric_limits<unsigned short>::max())
+    return static_cast<unsigned short>(0);
+  else
+#endif // _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
+    return static_cast<unsigned int>(0);
 }
 
 template <size_t _NumAlts>
-using __variant_index_t =
-#  ifndef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
-    unsigned int;
-#  else
-    std::tuple_element_t< __choose_index_type(_NumAlts), std::tuple<unsigned char, unsigned short, unsigned int> >;
-#  endif
+using __variant_index_t = decltype(std::__choose_index_type<_NumAlts>());
 
 template <class _IndexType>
 constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
@@ -1625,6 +1629,7 @@ _LIBCPP_POP_MACROS
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <exception>
+#  include <tuple>
 #  include <type_traits>
 #  include <typeinfo>
 #  include <utility>

diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -661,7 +661,6 @@ variant cstring
 variant initializer_list
 variant limits
 variant new
-variant tuple
 variant version
 vector array
 vector cctype

diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -661,7 +661,6 @@ variant cstring
 variant initializer_list
 variant limits
 variant new
-variant tuple
 variant version
 vector array
 vector cctype

diff --git a/libcxx/test/libcxx/utilities/variant/variant.variant/variant_size.pass.cpp b/libcxx/test/libcxx/utilities/variant/variant.variant/variant_size.pass.cpp
@@ -49,13 +49,13 @@ void test_index_type() {
 template <class IndexType>
 void test_index_internals() {
   using Lim = std::numeric_limits<IndexType>;
-  static_assert(std::__choose_index_type(Lim::max() -1) !=
-                std::__choose_index_type(Lim::max()), "");
-  static_assert(std::is_same_v<
-      std::__variant_index_t<Lim::max()-1>,
-      std::__variant_index_t<Lim::max()>
-    > == ExpectEqual, "");
-  using IndexT = std::__variant_index_t<Lim::max()-1>;
+#ifdef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
+  static_assert(!std::is_same_v<decltype(std::__choose_index_type<Lim::max() - 1>()),
+                                decltype(std::__choose_index_type<Lim::max()>())>);
+#endif
+  static_assert(
+      std::is_same_v<std::__variant_index_t<Lim::max() - 1>, std::__variant_index_t<Lim::max()> > == ExpectEqual, "");
+  using IndexT   = std::__variant_index_t<Lim::max() - 1>;
   using IndexLim = std::numeric_limits<IndexT>;
   static_assert(std::__variant_npos<IndexT> == IndexLim::max(), "");
 }

diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.elem/tuple.by.type.verify.cpp b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.elem/tuple.by.type.verify.cpp
@@ -18,13 +18,13 @@ struct UserType {};
 
 void test_bad_index() {
     std::tuple<long, long, char, std::string, char, UserType, char> t1;
-    TEST_IGNORE_NODISCARD std::get<int>(t1); // expected-error@tuple:* {{type not found}}
+    TEST_IGNORE_NODISCARD std::get<int>(t1); // expected-error@*:* {{type not found}}
     TEST_IGNORE_NODISCARD std::get<long>(t1); // expected-note {{requested here}}
     TEST_IGNORE_NODISCARD std::get<char>(t1); // expected-note {{requested here}}
-        // expected-error@tuple:* 2 {{type occurs more than once}}
+        // expected-error@*:* 2 {{type occurs more than once}}
     std::tuple<> t0;
     TEST_IGNORE_NODISCARD std::get<char*>(t0); // expected-node {{requested here}}
-        // expected-error@tuple:* 1 {{type not in empty type list}}
+        // expected-error@*:* {{type not in empty type list}}
 }
 
 void test_bad_return_type() {

diff --git a/libcxx/test/std/utilities/variant/variant.visit.member/visit.pass.cpp b/libcxx/test/std/utilities/variant/variant.visit.member/visit.pass.cpp
@@ -21,6 +21,7 @@
 #include <cassert>
 #include <memory>
 #include <string>
+#include <tuple>
 #include <type_traits>
 #include <utility>
 #include <variant>

diff --git a/libcxx/test/std/utilities/variant/variant.visit.member/visit_return_type.pass.cpp b/libcxx/test/std/utilities/variant/variant.visit.member/visit_return_type.pass.cpp
@@ -22,6 +22,7 @@
 #include <memory>
 #include <string>
 #include <type_traits>
+#include <tuple>
 #include <utility>
 #include <variant>
 

diff --git a/libcxx/test/std/utilities/variant/variant.visit/visit.pass.cpp b/libcxx/test/std/utilities/variant/variant.visit/visit.pass.cpp
@@ -15,6 +15,7 @@
 #include <cassert>
 #include <memory>
 #include <string>
+#include <tuple>
 #include <type_traits>
 #include <utility>
 #include <variant>

diff --git a/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp b/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp
@@ -15,6 +15,7 @@
 #include <cassert>
 #include <memory>
 #include <string>
+#include <tuple>
 #include <type_traits>
 #include <utility>
 #include <variant>