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