mirror of
https://github.com/capstone-engine/llvm-capstone.git
synced 2024-12-28 02:37:37 +00:00
64a9c944fc
This reverts commit 1ac403bd14, which
broke some non-libc++ build bots because they use an ancient CMake.
104 lines
3.8 KiB
C++
104 lines
3.8 KiB
C++
//===------------------------- barrier.cpp ---------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include <__config>
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#ifndef _LIBCPP_HAS_NO_THREADS
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#include <barrier>
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#include <thread>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if !defined(_LIBCPP_HAS_NO_TREE_BARRIER) && (_LIBCPP_STD_VER > 11)
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class __barrier_algorithm_base {
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public:
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struct alignas(64) /* naturally-align the heap state */ __state_t
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{
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struct {
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__atomic_base<__barrier_phase_t> __phase = ATOMIC_VAR_INIT(0);
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} __tickets[64];
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};
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ptrdiff_t& __expected;
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unique_ptr<char[]> __state_allocation;
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__state_t* __state;
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_LIBCPP_HIDDEN
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__barrier_algorithm_base(ptrdiff_t& __expected)
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: __expected(__expected)
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{
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size_t const __count = (__expected + 1) >> 1;
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size_t const __size = sizeof(__state_t) * __count;
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size_t __allocation_size = __size + alignof(__state_t);
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__state_allocation = unique_ptr<char[]>(new char[__allocation_size]);
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void* __allocation = __state_allocation.get();
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void* const __state_ = align(alignof(__state_t), __size, __allocation, __allocation_size);
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__state = new (__state_) __barrier_algorithm_base::__state_t[__count];
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}
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_LIBCPP_HIDDEN
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bool __arrive(__barrier_phase_t __old_phase)
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{
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__barrier_phase_t const __half_step = __old_phase + 1,
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__full_step = __old_phase + 2;
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size_t __current_expected = __expected,
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__current = hash<thread::id>()(this_thread::get_id()) % ((__expected + 1) >> 1);
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for(int __round = 0;; ++__round) {
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if(__current_expected <= 1)
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return true;
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size_t const __end_node = ((__current_expected + 1) >> 1),
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__last_node = __end_node - 1;
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for(;;++__current) {
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if(__current == __end_node)
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__current = 0;
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__barrier_phase_t expect = __old_phase;
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if(__current == __last_node && (__current_expected & 1))
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{
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if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __full_step, memory_order_acq_rel))
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break; // I'm 1 in 1, go to next __round
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}
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else if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __half_step, memory_order_acq_rel))
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{
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return false; // I'm 1 in 2, done with arrival
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}
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else if(expect == __half_step)
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{
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if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __full_step, memory_order_acq_rel))
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break; // I'm 2 in 2, go to next __round
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}
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}
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__current_expected = __last_node + 1;
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__current >>= 1;
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}
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}
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};
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_LIBCPP_EXPORTED_FROM_ABI
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__barrier_algorithm_base * __construct_barrier_algorithm_base(ptrdiff_t& __expected)
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{
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return new __barrier_algorithm_base(__expected);
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}
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_LIBCPP_EXPORTED_FROM_ABI
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bool __arrive_barrier_algorithm_base(__barrier_algorithm_base* __barrier,
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__barrier_phase_t __old_phase)
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{
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return __barrier->__arrive(__old_phase);
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}
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_LIBCPP_EXPORTED_FROM_ABI
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void __destroy_barrier_algorithm_base(__barrier_algorithm_base* __barrier)
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{
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delete __barrier;
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}
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#endif //!defined(_LIBCPP_HAS_NO_TREE_BARRIER) && (_LIBCPP_STD_VER >= 11)
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_LIBCPP_END_NAMESPACE_STD
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#endif //_LIBCPP_HAS_NO_THREADS
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