1 //===-- llvm/Support/AtomicOrdering.h ---Atomic Ordering---------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
10 /// Atomic ordering constants.
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.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_SUPPORT_ATOMICORDERING_H
18 #define LLVM_SUPPORT_ATOMICORDERING_H
24 /// Atomic ordering for C11 / C++11's memody models.
26 /// These values cannot change because they are shared with standard library
27 /// implementations as well as with other compilers.
28 enum class AtomicOrderingCABI {
37 bool operator<(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
38 bool operator>(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
39 bool operator<=(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
40 bool operator>=(AtomicOrderingCABI, AtomicOrderingCABI) = delete;
42 // Validate an integral value which isn't known to fit within the enum's range
43 // is a valid AtomicOrderingCABI.
44 template <typename Int> inline bool isValidAtomicOrderingCABI(Int I) {
45 return (Int)AtomicOrderingCABI::relaxed <= I &&
46 I <= (Int)AtomicOrderingCABI::seq_cst;
49 /// Atomic ordering for LLVM's memory model.
51 /// C++ defines ordering as a lattice. LLVM supplements this with NotAtomic and
52 /// Unordered, which are both below the C++ orders.
54 /// not_atomic-->unordered-->relaxed-->release--------------->acq_rel-->seq_cst
55 /// \-->consume-->acquire--/
56 enum class AtomicOrdering : unsigned {
59 Monotonic = 2, // Equivalent to C++'s relaxed.
60 // Consume = 3, // Not specified yet.
64 SequentiallyConsistent = 7,
65 LAST = SequentiallyConsistent
68 bool operator<(AtomicOrdering, AtomicOrdering) = delete;
69 bool operator>(AtomicOrdering, AtomicOrdering) = delete;
70 bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
71 bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
73 // Validate an integral value which isn't known to fit within the enum's range
74 // is a valid AtomicOrdering.
75 template <typename Int> inline bool isValidAtomicOrdering(Int I) {
76 return static_cast<Int>(AtomicOrdering::NotAtomic) <= I &&
77 I <= static_cast<Int>(AtomicOrdering::SequentiallyConsistent);
80 /// String used by LLVM IR to represent atomic ordering.
81 inline 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)];
88 /// Returns true if ao is stronger than other as defined by the AtomicOrdering
89 /// lattice, which is based on C++'s definition.
90 inline 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},
102 return lookup[static_cast<size_t>(ao)][static_cast<size_t>(other)];
105 inline 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},
117 return lookup[static_cast<size_t>(ao)][static_cast<size_t>(other)];
120 inline bool isStrongerThanUnordered(AtomicOrdering ao) {
121 return isStrongerThan(ao, AtomicOrdering::Unordered);
124 inline bool isStrongerThanMonotonic(AtomicOrdering ao) {
125 return isStrongerThan(ao, AtomicOrdering::Monotonic);
128 inline bool isAcquireOrStronger(AtomicOrdering ao) {
129 return isAtLeastOrStrongerThan(ao, AtomicOrdering::Acquire);
132 inline bool isReleaseOrStronger(AtomicOrdering ao) {
133 return isAtLeastOrStrongerThan(ao, AtomicOrdering::Release);
136 inline 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,
147 return lookup[static_cast<size_t>(ao)];
150 } // end namespace llvm
152 #endif // LLVM_SUPPORT_ATOMICORDERING_H