From 0d7924f2e766834e4fec84ff093f4c355fea6be1 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Wed, 12 Dec 2018 09:31:01 +0100 Subject: [PATCH] P0595R2 - is_constant_evaluated P0595R2 - is_constant_evaluated * include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED): Define if __builtin_is_constant_evaluated is available. * include/std/type_traits (std::is_constant_evaluated): New constexpr inline function. * testsuite/20_util/is_constant_evaluated/1.cc: New test. * testsuite/20_util/is_constant_evaluated/noexcept.cc: New test. From-SVN: r267045 --- libstdc++-v3/ChangeLog | 10 +++ libstdc++-v3/include/bits/c++config | 6 ++ libstdc++-v3/include/std/type_traits | 6 ++ .../20_util/is_constant_evaluated/1.cc | 80 +++++++++++++++++++ .../20_util/is_constant_evaluated/noexcept.cc | 23 ++++++ 5 files changed, 125 insertions(+) create mode 100644 libstdc++-v3/testsuite/20_util/is_constant_evaluated/1.cc create mode 100644 libstdc++-v3/testsuite/20_util/is_constant_evaluated/noexcept.cc diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 75ca6098da6..81dc78be260 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,13 @@ +2018-12-12 Jakub Jelinek + + P0595R2 - is_constant_evaluated + * include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED): + Define if __builtin_is_constant_evaluated is available. + * include/std/type_traits (std::is_constant_evaluated): New constexpr + inline function. + * testsuite/20_util/is_constant_evaluated/1.cc: New test. + * testsuite/20_util/is_constant_evaluated/noexcept.cc: New test. + 2018-12-10 Gerald Pfeifer * doc/xml/manual/documentation_hacking.xml: Update reference diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config index d499d32b51e..bab2bda34ef 100644 --- a/libstdc++-v3/include/bits/c++config +++ b/libstdc++-v3/include/bits/c++config @@ -627,6 +627,9 @@ namespace std # define _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP 1 # define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1 # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1 +# if __GNUC__ >= 9 +# define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1 +# endif #elif defined(__is_identifier) // For non-GNU compilers: # if ! __is_identifier(__has_unique_object_representations) @@ -638,6 +641,9 @@ namespace std # if ! __is_identifier(__builtin_launder) # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1 # endif +# if ! __is_identifier(__builtin_is_constant_evaluated) +# define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1 +# endif #endif // GCC // End of prewritten config; the settings discovered at configure time follow. diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 727a5451c56..2171d13bf3b 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -3029,6 +3029,12 @@ template template using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type; +#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED + constexpr inline bool + is_constant_evaluated() noexcept + { return __builtin_is_constant_evaluated(); } +#endif + #endif // C++2a _GLIBCXX_END_NAMESPACE_VERSION diff --git a/libstdc++-v3/testsuite/20_util/is_constant_evaluated/1.cc b/libstdc++-v3/testsuite/20_util/is_constant_evaluated/1.cc new file mode 100644 index 00000000000..c72574ead47 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/is_constant_evaluated/1.cc @@ -0,0 +1,80 @@ +// Copyright (C) 2018 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++2a" } +// { dg-do run { target c++2a } } + +#include +#include + +template +struct X { int v = N; }; +X x; // type X +int y = 4; +int a = std::is_constant_evaluated() ? y : 1; // initializes a to 1 +int b = std::is_constant_evaluated() ? 2 : y; // initializes b to 2 +int c = y + (std::is_constant_evaluated() ? 2 : y); // initializes c to 2*y +int d = std::is_constant_evaluated(); // initializes d to 1 +int e = d + std::is_constant_evaluated(); // initializes e to 1 + 0 + +constexpr int +foo(int x) +{ + const int n = std::is_constant_evaluated() ? 13 : 17; // n == 13 + int m = std::is_constant_evaluated() ? 13 : 17; // m might be 13 or 17 (see below) + char arr[n] = {}; // char[13] + return m + sizeof (arr) + x; +} + +constexpr int +bar() +{ + const int n = std::is_constant_evaluated() ? 13 : 17; + X x1; + X x2; + static_assert(std::is_same::value, + "x1/x2's type"); + return x1.v + x2.v; +} + +int p = foo(0); // m == 13; initialized to 26 +int q = p + foo(0); // m == 17 for this call; initialized to 56 +static_assert(bar() == 26, "bar"); + +struct S { int a, b; }; + +S s = { std::is_constant_evaluated() ? 2 : 3, y }; +S t = { std::is_constant_evaluated() ? 2 : 3, 4 }; + +static_assert(std::is_same >::value, "x's type"); + +void +test01() +{ + VERIFY( a == 1 && b == 2 && c == 8 && d == 1 && e == 1 && p == 26 ); + VERIFY( q == 56 && s.a == 3 && s.b == 4 && t.a == 2 && t.b == 4 ); + VERIFY( foo (y) == 34 ); + if constexpr (foo (0) != 26) + VERIFY( 0 ); + constexpr int w = foo (0); + VERIFY( w == 26 ); +} + +int main() +{ + test01(); +} diff --git a/libstdc++-v3/testsuite/20_util/is_constant_evaluated/noexcept.cc b/libstdc++-v3/testsuite/20_util/is_constant_evaluated/noexcept.cc new file mode 100644 index 00000000000..273cec91707 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/is_constant_evaluated/noexcept.cc @@ -0,0 +1,23 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } + +// Copyright (C) 2018 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +#include + +static_assert(noexcept(std::is_constant_evaluated())); -- 2.30.2