1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // This file is an internal atomic implementation, include base/atomicops.h
6 // instead. This file is for platforms that use GCC intrinsics rather than
7 // platform-specific assembly code for atomic operations.
8
9 #ifndef BASE_ATOMICOPS_INTERNALS_GCC_H_
10 #define BASE_ATOMICOPS_INTERNALS_GCC_H_
11
12 namespace base {
13 namespace subtle {
14
NoBarrier_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)15 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
16 Atomic32 old_value,
17 Atomic32 new_value) {
18 Atomic32 prev_value;
19 do {
20 if (__sync_bool_compare_and_swap(ptr, old_value, new_value))
21 return old_value;
22 prev_value = *ptr;
23 } while (prev_value == old_value);
24 return prev_value;
25 }
26
NoBarrier_AtomicExchange(volatile Atomic32 * ptr,Atomic32 new_value)27 inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
28 Atomic32 new_value) {
29 Atomic32 old_value;
30 do {
31 old_value = *ptr;
32 } while (!__sync_bool_compare_and_swap(ptr, old_value, new_value));
33 return old_value;
34 }
35
NoBarrier_AtomicIncrement(volatile Atomic32 * ptr,Atomic32 increment)36 inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
37 Atomic32 increment) {
38 return Barrier_AtomicIncrement(ptr, increment);
39 }
40
Barrier_AtomicIncrement(volatile Atomic32 * ptr,Atomic32 increment)41 inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
42 Atomic32 increment) {
43 for (;;) {
44 // Atomic exchange the old value with an incremented one.
45 Atomic32 old_value = *ptr;
46 Atomic32 new_value = old_value + increment;
47 if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
48 // The exchange took place as expected.
49 return new_value;
50 }
51 // Otherwise, *ptr changed mid-loop and we need to retry.
52 }
53 }
54
Acquire_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)55 inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
56 Atomic32 old_value,
57 Atomic32 new_value) {
58 // Since NoBarrier_CompareAndSwap uses __sync_bool_compare_and_swap, which
59 // is a full memory barrier, none is needed here or below in Release.
60 return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
61 }
62
Release_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)63 inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
64 Atomic32 old_value,
65 Atomic32 new_value) {
66 return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
67 }
68
NoBarrier_Store(volatile Atomic32 * ptr,Atomic32 value)69 inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
70 *ptr = value;
71 }
72
MemoryBarrier()73 inline void MemoryBarrier() {
74 __sync_synchronize();
75 }
76
Acquire_Store(volatile Atomic32 * ptr,Atomic32 value)77 inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
78 *ptr = value;
79 MemoryBarrier();
80 }
81
Release_Store(volatile Atomic32 * ptr,Atomic32 value)82 inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
83 MemoryBarrier();
84 *ptr = value;
85 }
86
NoBarrier_Load(volatile const Atomic32 * ptr)87 inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
88 return *ptr;
89 }
90
Acquire_Load(volatile const Atomic32 * ptr)91 inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
92 Atomic32 value = *ptr;
93 MemoryBarrier();
94 return value;
95 }
96
Release_Load(volatile const Atomic32 * ptr)97 inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
98 MemoryBarrier();
99 return *ptr;
100 }
101
102 } // namespace base::subtle
103 } // namespace base
104
105 #endif // BASE_ATOMICOPS_INTERNALS_GCC_H_
106
107