Update implementation of atomics with latest Chromium version but use compiler builtin atomics

src/base/atomicops_internals_ppc_gcc.h

-// Copyright 2012 the V8 project 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, use atomicops.h instead.
-//
-
-#ifndef V8_BASE_ATOMICOPS_INTERNALS_PPC_H_
-#define V8_BASE_ATOMICOPS_INTERNALS_PPC_H_
-
-namespace v8 {
-namespace base {
-
-inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
-                                         Atomic32 old_value,
-                                         Atomic32 new_value) {
-  return (__sync_val_compare_and_swap(ptr, old_value, new_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) == false);
-  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 (;;) {
-    Atomic32 old_value = *ptr;
-    Atomic32 new_value = old_value + increment;
-    if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
-      return new_value;
-      // The exchange took place as expected.
-    }
-    // Otherwise, *ptr changed mid-loop and we need to retry.
-  }
-}
-
-inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
-                                       Atomic32 old_value, Atomic32 new_value) {
-  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 Atomic8* ptr, Atomic8 value) {
-  *ptr = value;
-}
-
-inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
-  *ptr = value;
-}
-
-inline void MemoryBarrier() {
-  __asm__ __volatile__("sync" : : : "memory"); }
-
-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 Atomic8 NoBarrier_Load(volatile const Atomic8* ptr) { return *ptr; }
-
-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;
-}
-
-#ifdef V8_TARGET_ARCH_PPC64
-inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
-                                         Atomic64 old_value,
-                                         Atomic64 new_value) {
-  return (__sync_val_compare_and_swap(ptr, old_value, new_value));
-}
-
-inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
-                                         Atomic64 new_value) {
-  Atomic64 old_value;
-  do {
-    old_value = *ptr;
-  } while (__sync_bool_compare_and_swap(ptr, old_value, new_value) == false);
-  return old_value;
-}
-
-inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
-                                          Atomic64 increment) {
-  return Barrier_AtomicIncrement(ptr, increment);
-}
-
-inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
-                                        Atomic64 increment) {
-  for (;;) {
-    Atomic64 old_value = *ptr;
-    Atomic64 new_value = old_value + increment;
-    if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
-      return new_value;
-      // The exchange took place as expected.
-    }
-    // Otherwise, *ptr changed mid-loop and we need to retry.
-  }
-}
-
-inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
-                                       Atomic64 old_value, Atomic64 new_value) {
-  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
-}
-
-inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
-                                       Atomic64 old_value, Atomic64 new_value) {
-  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
-}
-
-inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
-  *ptr = value;
-}
-
-inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
-  *ptr = value;
-  MemoryBarrier();
-}
-
-inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
-  MemoryBarrier();
-  *ptr = value;
-}
-
-inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) { return *ptr; }
-
-inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
-  Atomic64 value = *ptr;
-  MemoryBarrier();
-  return value;
-}
-
-inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
-  MemoryBarrier();
-  return *ptr;
-}
-
-#endif
-}  // namespace base
-}  // namespace v8
-
-#endif  // V8_BASE_ATOMICOPS_INTERNALS_PPC_GCC_H_