Coverage Report

Created: 2022-07-16 07:03

/Users/buildslave/jenkins/workspace/coverage/llvm-project/libcxx/src/barrier.cpp
Line
Count
Source (jump to first uncovered line)
1
//===----------------------------------------------------------------------===//
2
//
3
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4
// See https://llvm.org/LICENSE.txt for license information.
5
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6
//
7
//===----------------------------------------------------------------------===//
8
9
#include <__config>
10
11
#ifndef _LIBCPP_HAS_NO_THREADS
12
13
#include <barrier>
14
#include <thread>
15
16
_LIBCPP_BEGIN_NAMESPACE_STD
17
18
#if !defined(_LIBCPP_HAS_NO_TREE_BARRIER)
19
20
class __barrier_algorithm_base {
21
public:
22
    struct alignas(64) /* naturally-align the heap state */ __state_t
23
    {
24
        struct {
25
          __atomic_base<__barrier_phase_t> __phase{0};
26
        } __tickets[64];
27
    };
28
29
    ptrdiff_t&              __expected;
30
    unique_ptr<__state_t[]> __state;
31
32
    _LIBCPP_HIDDEN
33
    __barrier_algorithm_base(ptrdiff_t& __expected)
34
        : __expected(__expected)
35
0
    {
36
0
        size_t const __count = (__expected + 1) >> 1;
37
0
        __state = unique_ptr<__state_t[]>(new __state_t[__count]);
38
0
    }
39
    _LIBCPP_HIDDEN
40
    bool __arrive(__barrier_phase_t __old_phase)
41
0
    {
42
0
        __barrier_phase_t const __half_step = __old_phase + 1,
43
0
                                __full_step = __old_phase + 2;
44
0
        size_t __current_expected = __expected,
45
0
            __current = hash<thread::id>()(this_thread::get_id()) % ((__expected + 1) >> 1);
46
0
        for(int __round = 0;; ++__round) {
47
0
            if(__current_expected <= 1)
48
0
                return true;
49
0
            size_t const __end_node = ((__current_expected + 1) >> 1),
50
0
                         __last_node = __end_node - 1;
51
0
            for(;;++__current) {
52
0
                if(__current == __end_node)
53
0
                __current = 0;
54
0
                __barrier_phase_t expect = __old_phase;
55
0
                if(__current == __last_node && (__current_expected & 1))
56
0
                {
57
0
                    if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __full_step, memory_order_acq_rel))
58
0
                        break;    // I'm 1 in 1, go to next __round
59
0
                }
60
0
                else if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __half_step, memory_order_acq_rel))
61
0
                {
62
0
                    return false; // I'm 1 in 2, done with arrival
63
0
                }
64
0
                else if(expect == __half_step)
65
0
                {
66
0
                    if(__state[__current].__tickets[__round].__phase.compare_exchange_strong(expect, __full_step, memory_order_acq_rel))
67
0
                        break;    // I'm 2 in 2, go to next __round
68
0
                }
69
0
            }
70
0
            __current_expected = __last_node + 1;
71
0
            __current >>= 1;
72
0
        }
73
0
    }
74
};
75
76
_LIBCPP_EXPORTED_FROM_ABI
77
__barrier_algorithm_base * __construct_barrier_algorithm_base(ptrdiff_t& __expected)
78
0
{
79
0
    return new __barrier_algorithm_base(__expected);
80
0
}
81
_LIBCPP_EXPORTED_FROM_ABI
82
bool __arrive_barrier_algorithm_base(__barrier_algorithm_base* __barrier,
83
                                     __barrier_phase_t __old_phase)
84
0
{
85
0
    return __barrier->__arrive(__old_phase);
86
0
}
87
_LIBCPP_EXPORTED_FROM_ABI
88
void __destroy_barrier_algorithm_base(__barrier_algorithm_base* __barrier)
89
0
{
90
0
    delete __barrier;
91
0
}
92
93
#endif // !defined(_LIBCPP_HAS_NO_TREE_BARRIER)
94
95
_LIBCPP_END_NAMESPACE_STD
96
97
#endif //_LIBCPP_HAS_NO_THREADS