@@ -30,6 +30,7 @@ std_headers = \
${std_srcdir}/any \
${std_srcdir}/array \
${std_srcdir}/atomic \
+ ${std_srcdir}/barrier \
${std_srcdir}/bit \
${std_srcdir}/bitset \
${std_srcdir}/charconv \
@@ -375,6 +375,7 @@ std_headers = \
${std_srcdir}/any \
${std_srcdir}/array \
${std_srcdir}/atomic \
+ ${std_srcdir}/barrier \
${std_srcdir}/bit \
${std_srcdir}/bitset \
${std_srcdir}/charconv \
@@ -566,13 +566,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
#if __cplusplus > 201703L
+ template<typename _Pred>
+ _GLIBCXX_ALWAYS_INLINE void
+ _M_wait(__int_type __old, _Pred&& __pred,
+ memory_order __m) const noexcept
+ {
+ std::__atomic_wait(&_M_i, __old,
+ std::forward<_Pred&&>(__pred));
+ }
+
_GLIBCXX_ALWAYS_INLINE void
wait(__int_type __old,
memory_order __m = memory_order_seq_cst) const noexcept
{
- std::__atomic_wait(&_M_i, __old,
- [__m, this, __old]()
- { return this->load(__m) != __old; });
+ _M_wait(__old, [__m, this, __old]()
+ { return this->load(__m) != __old; },
+ __m);
}
// TODO add const volatile overload
new file mode 100644
@@ -0,0 +1,230 @@
+// <barrier> -*- C++ -*-
+// This implementation is based on libcxx/include/barrier
+//===-- barrier.h --------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===---------------------------------------------------------------===//
+
+#ifndef _GLIBCXX_BARRIER
+#define _GLIBCXX_BARRIER 1
+
+#pragma GCC system_header
+
+#if __cplusplus > 201703L
+#define __cpp_lib_barrier 201907L
+
+#include <bits/c++config.h>
+
+#if defined(_GLIBCXX_HAS_GTHREADS)
+#include <bits/atomic_base.h>
+#include <bits/atomic_wait.h>
+#include <bits/functional_hash.h>
+#include <ext/numeric_traits.h>
+
+#include <memory>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+ struct __empty_completion
+ {
+ _GLIBCXX_ALWAYS_INLINE void
+ operator()() noexcept
+ { }
+ };
+
+/*
+
+The default implementation of __barrier_base is a classic tree barrier.
+
+It looks different from literature pseudocode for two main reasons:
+ 1. Threads that call into std::barrier functions do not provide indices,
+ so a numbering step is added before the actual barrier algorithm,
+ appearing as an N+1 round to the N rounds of the tree barrier.
+ 2. A great deal of attention has been paid to avoid cache line thrashing
+ by flattening the tree structure into cache-line sized arrays, that
+ are indexed in an efficient way.
+
+*/
+
+ using __barrier_phase_t = uint8_t;
+
+ template<class _CompletionF>
+ class __barrier_base
+ {
+ struct alignas(64) /* naturally-align the heap state */ __state_t
+ {
+ struct
+ {
+ __atomic_base<__barrier_phase_t> __phase = ATOMIC_VAR_INIT(0);
+ } __tickets[64];
+ };
+
+ ptrdiff_t _M_expected;
+ unique_ptr<char[]> _M_state_allocation;
+ __state_t* _M_state;
+ __atomic_base<ptrdiff_t> _M_expected_adjustment;
+ _CompletionF _M_completion;
+ __atomic_base<__barrier_phase_t> _M_phase;
+
+ static __gthread_t
+ _S_get_tid() noexcept
+ {
+#ifdef __GLIBC__
+ // For the GNU C library pthread_self() is usable without linking to
+ // libpthread.so but returns 0, so we cannot use it in single-threaded
+ // programs, because this_thread::get_id() != thread::id{} must be true.
+ // We know that pthread_t is an integral type in the GNU C library.
+ if (!__gthread_active_p())
+ return 1;
+#endif
+ return __gthread_self();
+ }
+
+ bool
+ _M_arrive(__barrier_phase_t __old_phase)
+ {
+ __barrier_phase_t const __half_step = __old_phase + 1,
+ __full_step = __old_phase + 2;
+ size_t __current_expected = _M_expected;
+ size_t __current = _Hash_impl::hash(_S_get_tid())
+ % ((_M_expected + 1) >> 1);
+ for (int __round = 0;; ++__round)
+ {
+ if (__current_expected <= 1)
+ return true;
+ size_t const __end_node = ((__current_expected + 1) >> 1),
+ __last_node = __end_node - 1;
+ for (;;++__current)
+ {
+ if (__current == __end_node)
+ __current = 0;
+ __barrier_phase_t __expect = __old_phase;
+ if (__current == __last_node && (__current_expected & 1))
+ {
+ if (_M_state[__current].__tickets[__round].__phase
+ .compare_exchange_strong(__expect, __full_step,
+ memory_order_acq_rel))
+ break; // I'm 1 in 1, go to next __round
+ }
+ else if (_M_state[__current].__tickets[__round].__phase
+ .compare_exchange_strong(__expect, __half_step,
+ memory_order_acq_rel))
+ {
+ return false; // I'm 1 in 2, done with arrival
+ }
+ else if (__expect == __half_step)
+ {
+ if (_M_state[__current].__tickets[__round].__phase
+ .compare_exchange_strong(__expect, __full_step,
+ memory_order_acq_rel))
+ break; // I'm 2 in 2, go to next __round
+ }
+ }
+ __current_expected = __last_node + 1;
+ __current >>= 1;
+ }
+ }
+
+ public:
+ using arrival_token = __barrier_phase_t;
+
+ static constexpr ptrdiff_t
+ max() noexcept
+ { return __gnu_cxx::__numeric_traits<ptrdiff_t>::__max; }
+
+ __barrier_base(ptrdiff_t __expected, _CompletionF __completion = _CompletionF())
+ : _M_expected(__expected), _M_expected_adjustment(0),
+ _M_completion(move(__completion)), _M_phase(0)
+ {
+ size_t const __count = (_M_expected + 1) >> 1;
+ size_t const __size = sizeof(__state_t) * __count;
+ size_t __allocation_size = __size + alignof(__state_t);
+ _M_state_allocation = unique_ptr<char[]>(new char[__allocation_size]);
+ void* __allocation = _M_state_allocation.get();
+ void* const __state = align(alignof(__state_t), __size, __allocation,
+ __allocation_size);
+ _M_state = new (__state) __state_t[__count];
+ }
+
+ [[nodiscard]] arrival_token
+ arrive(ptrdiff_t __update)
+ {
+ auto const __old_phase = _M_phase.load(memory_order_relaxed);
+ for(; __update; --__update)
+ {
+ if(_M_arrive(__old_phase))
+ {
+ _M_completion();
+ _M_expected += _M_expected_adjustment.load(memory_order_relaxed);
+ _M_expected_adjustment.store(0, memory_order_relaxed);
+ _M_phase.store(__old_phase + 2, memory_order_release);
+ _M_phase.notify_all();
+ }
+ }
+ return __old_phase;
+ }
+
+ void
+ wait(arrival_token&& __old_phase) const
+ {
+ auto const __test_fn = [=, this]
+ {
+ return _M_phase.load(memory_order_acquire) != __old_phase;
+ };
+ _M_phase._M_wait(__old_phase, __test_fn, memory_order_acquire);
+ }
+
+ void
+ arrive_and_drop()
+ {
+ _M_expected_adjustment.fetch_sub(1, memory_order_relaxed);
+ (void)arrive(1);
+ }
+ };
+
+ template<class _CompletionF = __empty_completion>
+ class barrier
+ {
+ __barrier_base<_CompletionF> _M_b;
+ public:
+ using arrival_token = typename __barrier_base<_CompletionF>::arrival_token;
+
+ static constexpr ptrdiff_t
+ max() noexcept
+ { return __barrier_base<_CompletionF>::max(); }
+
+ barrier(ptrdiff_t __count, _CompletionF __completion = _CompletionF())
+ : _M_b(__count, std::move(__completion))
+ { }
+
+ barrier(barrier const&) = delete;
+ barrier& operator=(barrier const&) = delete;
+
+ [[nodiscard]] arrival_token
+ arrive(ptrdiff_t __update = 1)
+ { return _M_b.arrive(__update); }
+
+ void
+ wait(arrival_token&& __phase) const
+ { _M_b.wait(std::move(__phase)); }
+
+ void
+ arrive_and_wait()
+ { wait(arrive()); }
+
+ void
+ arrive_and_drop()
+ { _M_b.arrive_and_drop(); }
+ };
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace
+#endif // _GLIBCXX_HAS_GTHREADS
+#endif // __cplusplus > 201703L
+#endif // _GLIBCXX_BARRIER
+
@@ -189,8 +189,6 @@
#endif
#define __cpp_lib_type_identity 201806L
#define __cpp_lib_unwrap_ref 201811L
-#define __cpp_lib_semaphore 201907L
-#define __cpp_lib_latch 201907L
#if _GLIBCXX_HOSTED
#undef __cpp_lib_array_constexpr
@@ -213,6 +211,9 @@
#define __cpp_lib_interpolate 201902L
#ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_jthread 201911L
+#define __cpp_lib_semaphore 201907L
+#define __cpp_lib_latch 201907L
+#define __cpp_lib_barrier 201907L
#endif
#define __cpp_lib_list_remove_return_type 201806L
#define __cpp_lib_math_constants 201907L
new file mode 100644
@@ -0,0 +1,27 @@
+// Copyright (C) 2020 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
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <barrier>
+
+#ifndef __cpp_lib_barrier
+# error "Feature-test macro for barrier missing in <barrier>"
+#elif __cpp_lib_barrier != 201907L
+# error "Feature-test macro for barrier has wrong value in <barrier>"
+#endif
new file mode 100644
@@ -0,0 +1,27 @@
+// Copyright (C) 2019-2020 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
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <version>
+
+#ifndef __cpp_lib_barrier
+# error "Feature-test macro for barrier missing in <version>"
+#elif __cpp_lib_barrier != 201907L
+# error "Feature-test macro for barrier has wrong value in <version>"
+#endif
new file mode 100644
@@ -0,0 +1,34 @@
+// This implementation is based on libcxx/test/std/thread/thread.barrier/arrive.pass.cpp
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// { dg-options "-std=gnu++2a -pthread" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target pthread }
+// { dg-require-gthreads "" }
+
+#include <barrier>
+#include <thread>
+
+#include <testsuite_hooks.h>
+
+int main(int, char**)
+{
+ std::barrier<> b(2);
+
+ auto tok = b.arrive();
+ std::thread t([&](){
+ (void)b.arrive();
+ });
+ b.wait(std::move(tok));
+ t.join();
+
+ auto tok2 = b.arrive(2);
+ b.wait(std::move(tok2));
+ return 0;
+}
new file mode 100644
@@ -0,0 +1,32 @@
+// This implementation is based on libcxx/test/std/thread/thread.barrier/arrive_and_drop.pass.cpp
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// { dg-options "-std=gnu++2a -pthread" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target pthread }
+// { dg-require-gthreads "" }
+
+#include <barrier>
+#include <thread>
+
+#include <testsuite_hooks.h>
+
+int main(int, char**)
+{
+ std::barrier<> b(2);
+
+ std::thread t([&](){
+ b.arrive_and_drop();
+ });
+
+ b.arrive_and_wait();
+ b.arrive_and_wait();
+ t.join();
+ return 0;
+}
new file mode 100644
@@ -0,0 +1,33 @@
+// This implementation is based on libcxx/test/std/thread/thread.barrier/arrive_and_drop.pass.cpp
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// { dg-options "-std=gnu++2a -pthread" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target pthread }
+// { dg-require-gthreads "" }
+
+#include <barrier>
+#include <thread>
+
+#include <testsuite_hooks.h>
+
+int main(int, char**)
+{
+ std::barrier<> b(2);
+
+ std::thread t([&](){
+ for(int i = 0; i < 10; ++i)
+ b.arrive_and_wait();
+ });
+ for(int i = 0; i < 10; ++i)
+ b.arrive_and_wait();
+ t.join();
+
+ return 0;
+}
new file mode 100644
@@ -0,0 +1,39 @@
+// This implementation is based on libcxx/test/std/thread/thread.barrier/completion.pass.cpp
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// { dg-options "-std=gnu++2a -pthread" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target pthread }
+// { dg-require-gthreads "" }
+
+#include <barrier>
+#include <thread>
+
+#include <testsuite_hooks.h>
+
+#include <iostream>
+
+int main(int, char**)
+{
+ int x = 0;
+ auto comp = [&] { x += 1; };
+ std::barrier<decltype(comp)> b(2, comp);
+
+ std::thread t([&](){
+ for(int i = 0; i < 10; ++i)
+ b.arrive_and_wait();
+ });
+
+ for(int i = 0; i < 10; ++i)
+ b.arrive_and_wait();
+
+ VERIFY( x == 10 );
+ t.join();
+ return 0;
+}
new file mode 100644
@@ -0,0 +1,26 @@
+// This implementation is based on libcxx/test/std/thread/thread.barrier/max.pass.cpp
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// { dg-options "-std=gnu++2a -pthread" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target pthread }
+// { dg-require-gthreads "" }
+
+#include <barrier>
+#include <thread>
+
+#include <testsuite_hooks.h>
+
+int main(int, char**)
+{
+ static_assert(std::barrier<>::max() > 0, "");
+ auto l = [](){};
+ static_assert(std::barrier<decltype(l)>::max() > 0, "");
+ return 0;
+}