[libcxx-commits] [PATCH] D132509: [libc++] Use _Lazy in tuple constructors

[Louis Dionne via Phabricator via libcxx-commits]

ldionne created this revision.
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This reduces the number of instantiations and also avoid blowing up
past the fold-expression limit of Clang.

This is NOT a general statement that we should strive to stay within
Clang's (sometimes way too small) limits, however in this case the
change will reduce the number of template instantiations while at the
same time doing that, which is good.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D132509

Files:
  libcxx/include/tuple
  libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp


Index: libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp
===================================================================
--- libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp
+++ libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp
@@ -17,9 +17,17 @@
 
 template <size_t... I>
 constexpr void CreateTuple(std::index_sequence<I...>) {
-  std::tuple<decltype(I)...> tuple(I...);
+  using LargeTuple = std::tuple<decltype(I)...>;
+  LargeTuple tuple(I...);
   assert(std::get<0>(tuple) == 0);
   assert(std::get<sizeof...(I)-1>(tuple) == sizeof...(I)-1);
+  LargeTuple t2 = tuple;            // copy constructor
+  LargeTuple t3 = std::move(tuple); // move constructor
+  LargeTuple t4;                    // default constructor
+  t3 = t2;                          // copy assignment
+  t4 = std::move(t2);               // move assignment
+  swap(t3, t4);                     // swap
+  // equality (t3 == t4) does not work
 }
 
 constexpr bool test() {
Index: libcxx/include/tuple
===================================================================
--- libcxx/include/tuple
+++ libcxx/include/tuple
@@ -844,13 +844,13 @@
     template <class... _Up, enable_if_t<
         _EnableCtorFromUTypesTuple<tuple<_Up...>&>::value>* = nullptr>
     _LIBCPP_HIDE_FROM_ABI constexpr
-        explicit(!(is_convertible_v<_Up&, _Tp> && ...))
+        explicit(!_Lazy<_And, is_convertible<_Up&, _Tp>...>::value)
     tuple(tuple<_Up...>& __t) : __base_(__t) {}
 
     template <class _Alloc, class... _Up, enable_if_t<
         _EnableCtorFromUTypesTuple<tuple<_Up...>&>::value>* = nullptr>
     _LIBCPP_HIDE_FROM_ABI constexpr
-        explicit(!(is_convertible_v<_Up&, _Tp> && ...))
+        explicit(!_Lazy<_And, is_convertible<_Up&, _Tp>...>::value)
     tuple(allocator_arg_t, const _Alloc& __alloc, tuple<_Up...>& __t) : __base_(allocator_arg_t(), __alloc, __t) {}
 #endif // _LIBCPP_STD_VER > 20
 
@@ -908,13 +908,13 @@
     template <class... _Up, enable_if_t<
         _EnableCtorFromUTypesTuple<const tuple<_Up...>&&>::value>* = nullptr>
     _LIBCPP_HIDE_FROM_ABI constexpr
-        explicit(!(is_convertible_v<const _Up&&, _Tp> && ...))
+        explicit(!_Lazy<_And, is_convertible<const _Up&&, _Tp>...>::value)
     tuple(const tuple<_Up...>&& __t) : __base_(std::move(__t)) {}
 
     template <class _Alloc, class... _Up, enable_if_t<
         _EnableCtorFromUTypesTuple<const tuple<_Up...>&&>::value>* = nullptr>
     _LIBCPP_HIDE_FROM_ABI constexpr
-        explicit(!(is_convertible_v<const _Up&&, _Tp> && ...))
+        explicit(!_Lazy<_And, is_convertible<const _Up&&, _Tp>...>::value)
     tuple(allocator_arg_t, const _Alloc& __alloc, const tuple<_Up...>&& __t)
         : __base_(allocator_arg_t(), __alloc, std::move(__t)) {}
 #endif // _LIBCPP_STD_VER > 20


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