Mercurial > hg > CbC > CbC_gcc
view gcc/testsuite/g++.dg/tree-ssa/pr69336.C @ 145:1830386684a0
gcc-9.2.0
author | anatofuz |
---|---|
date | Thu, 13 Feb 2020 11:34:05 +0900 |
parents | 04ced10e8804 |
children |
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// { dg-do compile } // { dg-options "-O3 -fdump-tree-optimized -std=c++14" } #include <array> #include <utility> #include <stdexcept> template<class Key, class T, size_t N> struct static_map { using key_type = Key; using mapped_type = T; using value_type = std::pair<const key_type, mapped_type>; private: using _value_type = std::pair<size_t, value_type>; _value_type _values[N]; static constexpr _value_type _new_value_type(const std::pair<Key, T> &v) { return std::make_pair(0, std::make_pair(v.first, v.second)); } public: template<class... U> constexpr static_map(U &&...il) : _values{ _new_value_type(il)... } { } constexpr mapped_type &operator[](const key_type &k) { return at(k); } constexpr const mapped_type &operator[](const key_type &k) const { return at(k); } constexpr mapped_type &at(const key_type &k) { for (size_t n = 0; n < N; n++) if (_values[n].second.first == k) return _values[n].second.second; throw std::out_of_range("Key not found"); } constexpr const mapped_type &at(const key_type &k) const { for (size_t n = 0; n < N; n++) if (_values[n].second.first == k) return _values[n].second.second; throw std::out_of_range("Key not found"); } }; namespace detail { template<class Key, class T, size_t N, size_t... I> constexpr static_map<Key, T, N> static_map_from_array(const std::pair<Key, T>(&il)[N], std::index_sequence<I...>) { return static_map<Key, T, N>(il[I]...); } } template<class Key, class T, size_t N> constexpr static_map<Key, T, N> make_static_map(const std::pair<Key, T> (&il)[N]) { return detail::static_map_from_array<Key, T, N>(il, std::make_index_sequence<N>()); } /* Two phase construction, required because heterogeneous braced init in C++ 14 has a big limitation: template<class... Args> auto make(Args &&...) will accept make({ 5, "apple" }) as make(int, const char *) but make({ 5, "apple" }, { 8, "pear" }) will fail to deduce Args as a heterogeneous initializer_list is not permitted. This forces something like make(make_pair{ 5, "apple" }, make_pair{ 8, "pear" }, ...) which is less succinct than using a constexpr C array for the nested braced init. */ constexpr std::pair<const int, const char *> map_data[] = { { 5, "apple" }, { 8, "pear" }, { 0, "banana" } }; template<size_t N> constexpr int cstrcmp(const char *a, const char *b) { for (size_t n = 0; n < N; n++) { if (a[n] < b[n]) return -1; if (a[n] > b[n]) return 1; } return 0; } int main(void) { constexpr auto cmap = make_static_map(map_data); // No abort() appears in assembler, so this was executed constexpr if(!cmap[8]) abort(); // This however does cause code implementing a lookup to be generated, // so this was NOT executed constexpr //const char *foo=cmap[5]; return 0; } // { dg-final { scan-tree-dump-not "cmap" "optimized" { target x86_64-*-* i?86-*-* } } }