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- // Copyright (c) 2009 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- // This file is an internal atomic implementation, include butil/atomicops.h
- // instead. This file is for platforms that use GCC intrinsics rather than
- // platform-specific assembly code for atomic operations.
- #ifndef BUTIL_ATOMICOPS_INTERNALS_GCC_H_
- #define BUTIL_ATOMICOPS_INTERNALS_GCC_H_
- namespace butil {
- namespace subtle {
- inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
- Atomic32 old_value,
- Atomic32 new_value) {
- Atomic32 prev_value;
- do {
- if (__sync_bool_compare_and_swap(ptr, old_value, new_value))
- return old_value;
- prev_value = *ptr;
- } while (prev_value == old_value);
- return prev_value;
- }
- inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
- Atomic32 new_value) {
- Atomic32 old_value;
- do {
- old_value = *ptr;
- } while (!__sync_bool_compare_and_swap(ptr, old_value, new_value));
- return old_value;
- }
- inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
- Atomic32 increment) {
- return Barrier_AtomicIncrement(ptr, increment);
- }
- inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
- Atomic32 increment) {
- for (;;) {
- // Atomic exchange the old value with an incremented one.
- Atomic32 old_value = *ptr;
- Atomic32 new_value = old_value + increment;
- if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
- // The exchange took place as expected.
- return new_value;
- }
- // Otherwise, *ptr changed mid-loop and we need to retry.
- }
- }
- inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
- Atomic32 old_value,
- Atomic32 new_value) {
- // Since NoBarrier_CompareAndSwap uses __sync_bool_compare_and_swap, which
- // is a full memory barrier, none is needed here or below in Release.
- return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
- }
- inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
- Atomic32 old_value,
- Atomic32 new_value) {
- return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
- }
- inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
- *ptr = value;
- }
- inline void MemoryBarrier() {
- __sync_synchronize();
- }
- inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
- *ptr = value;
- MemoryBarrier();
- }
- inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
- MemoryBarrier();
- *ptr = value;
- }
- inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
- return *ptr;
- }
- inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
- Atomic32 value = *ptr;
- MemoryBarrier();
- return value;
- }
- inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
- MemoryBarrier();
- return *ptr;
- }
- } // namespace butil::subtle
- } // namespace butil
- #endif // BUTIL_ATOMICOPS_INTERNALS_GCC_H_
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