1//===-- llvm/Support/AtomicOrdering.h ---Atomic Ordering---------*- C++ -*-===//
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/// \file
10/// Atomic ordering constants.
11///
12/// These values are used by LLVM to represent atomic ordering for C++11's
13/// memory model and more, as detailed in docs/Atomics.rst.
14///
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_SUPPORT_ATOMICORDERING_H
18#define LLVM_SUPPORT_ATOMICORDERING_H
19
20#include <cstddef>
21
22namespace llvm {
23
24/// Atomic ordering for C11 / C++11's memory models.
25///
26/// These values cannot change because they are shared with standard library
27/// implementations as well as with other compilers.
28enum class AtomicOrderingCABI {
29 relaxed = 0,
30 consume = 1,
31 acquire = 2,
32 release = 3,
33 acq_rel = 4,
34 seq_cst = 5,
35};
36
37bool operator<(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
38bool operator>(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
39bool operator<=(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
40bool operator>=(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
41
42// Validate an integral value which isn't known to fit within the enum's range
43// is a valid AtomicOrderingCABI.
44template <typename Int> inline bool isValidAtomicOrderingCABI(Int I) {
45 return (Int)AtomicOrderingCABI::relaxed <= I &&
46 I <= (Int)AtomicOrderingCABI::seq_cst;
47}
48
49/// Atomic ordering for LLVM's memory model.
50///
51/// C++ defines ordering as a lattice. LLVM supplements this with NotAtomic and
52/// Unordered, which are both below the C++ orders.
53///
54/// not_atomic-->unordered-->relaxed-->release--------------->acq_rel-->seq_cst
55/// \-->consume-->acquire--/
56enum class AtomicOrdering : unsigned {
57 NotAtomic = 0,
58 Unordered = 1,
59 Monotonic = 2, // Equivalent to C++'s relaxed.
60 // Consume = 3, // Not specified yet.
61 Acquire = 4,
62 Release = 5,
63 AcquireRelease = 6,
64 SequentiallyConsistent = 7,
65 LAST = SequentiallyConsistent
66};
67
68bool operator<(AtomicOrdering, AtomicOrdering) = delete;
69bool operator>(AtomicOrdering, AtomicOrdering) = delete;
70bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
71bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
72
73// Validate an integral value which isn't known to fit within the enum's range
74// is a valid AtomicOrdering.
75template <typename Int> inline bool isValidAtomicOrdering(Int I) {
76 return static_cast<Int>(AtomicOrdering::NotAtomic) <= I &&
77 I <= static_cast<Int>(AtomicOrdering::SequentiallyConsistent);
78}
79
80/// String used by LLVM IR to represent atomic ordering.
81inline const char *toIRString(AtomicOrdering ao) {
82 static const char *names[8] = {"not_atomic", "unordered", "monotonic",
83 "consume", "acquire", "release",
84 "acq_rel", "seq_cst"};
85 return names[static_cast<size_t>(ao)];
86}
87
88/// Returns true if ao is stronger than other as defined by the AtomicOrdering
89/// lattice, which is based on C++'s definition.
90inline bool isStrongerThan(AtomicOrdering AO, AtomicOrdering Other) {
91 static const bool lookup[8][8] = {
92 // NA UN RX CO AC RE AR SC
93 /* NotAtomic */ {false, false, false, false, false, false, false, false},
94 /* Unordered */ { true, false, false, false, false, false, false, false},
95 /* relaxed */ { true, true, false, false, false, false, false, false},
96 /* consume */ { true, true, true, false, false, false, false, false},
97 /* acquire */ { true, true, true, true, false, false, false, false},
98 /* release */ { true, true, true, false, false, false, false, false},
99 /* acq_rel */ { true, true, true, true, true, true, false, false},
100 /* seq_cst */ { true, true, true, true, true, true, true, false},
101 };
102 return lookup[static_cast<size_t>(AO)][static_cast<size_t>(Other)];
103}
104
105inline bool isAtLeastOrStrongerThan(AtomicOrdering AO, AtomicOrdering Other) {
106 static const bool lookup[8][8] = {
107 // NA UN RX CO AC RE AR SC
108 /* NotAtomic */ { true, false, false, false, false, false, false, false},
109 /* Unordered */ { true, true, false, false, false, false, false, false},
110 /* relaxed */ { true, true, true, false, false, false, false, false},
111 /* consume */ { true, true, true, true, false, false, false, false},
112 /* acquire */ { true, true, true, true, true, false, false, false},
113 /* release */ { true, true, true, false, false, true, false, false},
114 /* acq_rel */ { true, true, true, true, true, true, true, false},
115 /* seq_cst */ { true, true, true, true, true, true, true, true},
116 };
117 return lookup[static_cast<size_t>(AO)][static_cast<size_t>(Other)];
118}
119
120inline bool isStrongerThanUnordered(AtomicOrdering AO) {
121 return isStrongerThan(AO, AtomicOrdering::Unordered);
122}
123
124inline bool isStrongerThanMonotonic(AtomicOrdering AO) {
125 return isStrongerThan(AO, AtomicOrdering::Monotonic);
126}
127
128inline bool isAcquireOrStronger(AtomicOrdering AO) {
129 return isAtLeastOrStrongerThan(AO, AtomicOrdering::Acquire);
130}
131
132inline bool isReleaseOrStronger(AtomicOrdering AO) {
133 return isAtLeastOrStrongerThan(AO, AtomicOrdering::Release);
134}
135
136inline AtomicOrderingCABI toCABI(AtomicOrdering AO) {
137 static const AtomicOrderingCABI lookup[8] = {
138 /* NotAtomic */ AtomicOrderingCABI::relaxed,
139 /* Unordered */ AtomicOrderingCABI::relaxed,
140 /* relaxed */ AtomicOrderingCABI::relaxed,
141 /* consume */ AtomicOrderingCABI::consume,
142 /* acquire */ AtomicOrderingCABI::acquire,
143 /* release */ AtomicOrderingCABI::release,
144 /* acq_rel */ AtomicOrderingCABI::acq_rel,
145 /* seq_cst */ AtomicOrderingCABI::seq_cst,
146 };
147 return lookup[static_cast<size_t>(AO)];
148}
149
150} // end namespace llvm
151
152#endif // LLVM_SUPPORT_ATOMICORDERING_H
153