PR libstdc++/69724 avoid temporary in std::thread construction
The std::thread constructor creates (and then moves) an unnecessary temporary copy of each argument. Optimize it to only make the one copy that is required. PR libstdc++/69724 * include/std/thread (thread::_State_impl, thread::_S_make_state): Replace single _Callable parameter with variadic _Args pack, to forward them directly to the tuple of decayed copies. * testsuite/30_threads/thread/cons/69724.cc: New test. From-SVN: r271166
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@ -1,3 +1,11 @@
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2019-05-14 Jonathan Wakely <jwakely@redhat.com>
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PR libstdc++/69724
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* include/std/thread (thread::_State_impl, thread::_S_make_state):
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Replace single _Callable parameter with variadic _Args pack, to
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forward them directly to the tuple of decayed copies.
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* testsuite/30_threads/thread/cons/69724.cc: New test.
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2019-05-14 Nina Dinka Ranns <dinka.ranns@gmail.com>
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Inconsistency wrt Allocators in basic_string assignment (LWG2579)
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@ -127,9 +127,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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#else
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auto __depend = nullptr;
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#endif
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_M_start_thread(_S_make_state(
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__make_invoker(std::forward<_Callable>(__f),
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std::forward<_Args>(__args)...)),
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// A call wrapper holding tuple{DECAY_COPY(__f), DECAY_COPY(__args)...}
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using _Invoker_type = _Invoker<__decayed_tuple<_Callable, _Args...>>;
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_M_start_thread(_S_make_state<_Invoker_type>(
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std::forward<_Callable>(__f), std::forward<_Args>(__args)...),
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__depend);
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}
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@ -188,8 +190,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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{
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_Callable _M_func;
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_State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
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{ }
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template<typename... _Args>
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_State_impl(_Args&&... __args)
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: _M_func{{std::forward<_Args>(__args)...}}
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{ }
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void
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_M_run() { _M_func(); }
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@ -198,12 +202,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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void
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_M_start_thread(_State_ptr, void (*)());
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template<typename _Callable>
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template<typename _Callable, typename... _Args>
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static _State_ptr
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_S_make_state(_Callable&& __f)
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_S_make_state(_Args&&... __args)
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{
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using _Impl = _State_impl<_Callable>;
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return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
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return _State_ptr{new _Impl{std::forward<_Args>(__args)...}};
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}
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#if _GLIBCXX_THREAD_ABI_COMPAT
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public:
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@ -0,0 +1,70 @@
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// Copyright (C) 2019 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-do run }
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// { dg-options "-pthread" }
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// { dg-require-effective-target c++11 }
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// { dg-require-effective-target pthread }
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// { dg-require-gthreads "" }
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#include <thread>
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#include <testsuite_rvalref.h>
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struct F : __gnu_test::copycounter
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{
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F() = default;
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F(const F&) = default;
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// Move constructor copies base class, to use counter:
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F(F&& f) : copycounter(f) { f.valid = false; }
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void run() { VERIFY(this->valid); }
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};
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void
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test01()
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{
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std::thread{&F::run, F{}}.join();
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VERIFY( F::copycount == 1 );
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}
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void
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test02()
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{
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F::copycount = 0;
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const F f;
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std::thread{&F::run, f}.join();
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VERIFY( F::copycount == 1 );
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}
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void
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test03()
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{
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F::copycount = 0;
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F f;
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std::thread{&F::run, std::ref(f)}.join();
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VERIFY( F::copycount == 0 );
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}
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int
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main()
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{
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test01();
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test02();
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test03();
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}
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