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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 base/atomicops.h
// instead. This file is for platforms that use GCC intrinsics rather than
// platform-specific assembly code for atomic operations.
#ifndef BASE_ATOMICOPS_INTERNALS_GCC_H_
#define BASE_ATOMICOPS_INTERNALS_GCC_H_
namespace base {
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 base::subtle
} // namespace base
#endif // BASE_ATOMICOPS_INTERNALS_GCC_H_
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