Revert of Remove old/unused atomicops code

base/atomicops_internals_arm64_gcc.h

+// Copyright 2014 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, use base/atomicops.h instead.
+
+// TODO(rmcilroy): Investigate whether we can use __sync__ intrinsics instead of
+//                 the hand coded assembly without introducing perf regressions.
+// TODO(rmcilroy): Investigate whether we can use acquire / release versions of
+//                 exclusive load / store assembly instructions and do away with
+//                 the barriers.
+
+#ifndef BASE_ATOMICOPS_INTERNALS_ARM64_GCC_H_
+#define BASE_ATOMICOPS_INTERNALS_ARM64_GCC_H_
+
+#if defined(OS_QNX)
+#include <sys/cpuinline.h>
+#endif
+
+namespace base {
+namespace subtle {
+
+inline void MemoryBarrier() {
+  __asm__ __volatile__ ("dmb ish" ::: "memory");  // NOLINT
+}
+
+// NoBarrier versions of the operation include "memory" in the clobber list.
+// This is not required for direct usage of the NoBarrier versions of the
+// operations. However this is required for correctness when they are used as
+// part of the Acquire or Release versions, to ensure that nothing from outside
+// the call is reordered between the operation and the memory barrier. This does
+// not change the code generated, so has no or minimal impact on the
+// NoBarrier operations.
+
+inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
+                                         Atomic32 old_value,
+                                         Atomic32 new_value) {
+  Atomic32 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[prev], %[ptr]                 \n\t"  // Load the previous value.
+    "cmp %w[prev], %w[old_value]           \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %w[new_value], %[ptr]  \n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    "1:                                    \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [old_value]"IJr" (old_value),
+      [new_value]"r" (new_value)
+    : "cc", "memory"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
+                                         Atomic32 new_value) {
+  Atomic32 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[result], %[ptr]               \n\t"  // Load the previous value.
+    "stxr %w[temp], %w[new_value], %[ptr]  \n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [new_value]"r" (new_value)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
+                                          Atomic32 increment) {
+  Atomic32 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                       \n\t"
+    "ldxr %w[result], %[ptr]                  \n\t"  // Load the previous value.
+    "add %w[result], %w[result], %w[increment]\n\t"
+    "stxr %w[temp], %w[result], %[ptr]        \n\t"  // Try to store the result.
+    "cbnz %w[temp], 0b                        \n\t"  // Retry on failure.
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [increment]"IJr" (increment)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
+                                        Atomic32 increment) {
+  MemoryBarrier();
+  Atomic32 result = NoBarrier_AtomicIncrement(ptr, increment);
+  MemoryBarrier();
+
+  return result;
+}
+
+inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  Atomic32 prev = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+  MemoryBarrier();
+
+  return prev;
+}
+
+inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  MemoryBarrier();
+  Atomic32 prev = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+
+  return prev;
+}
+
+inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+}
+
+inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+  MemoryBarrier();
+}
+
+inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
+  __asm__ __volatile__ (  // NOLINT
+    "stlr %w[value], %[ptr]  \n\t"
+    : [ptr]"=Q" (*ptr)
+    : [value]"r" (value)
+    : "memory"
+  );  // NOLINT
+}
+
+inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
+  return *ptr;
+}
+
+inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
+  Atomic32 value;
+
+  __asm__ __volatile__ (  // NOLINT
+    "ldar %w[value], %[ptr]  \n\t"
+    : [value]"=r" (value)
+    : [ptr]"Q" (*ptr)
+    : "memory"
+  );  // NOLINT
+
+  return value;
+}
+
+inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
+  MemoryBarrier();
+  return *ptr;
+}
+
+// 64-bit versions of the operations.
+// See the 32-bit versions for comments.
+
+inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
+                                         Atomic64 old_value,
+                                         Atomic64 new_value) {
+  Atomic64 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[prev], %[ptr]                  \n\t"
+    "cmp %[prev], %[old_value]             \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %[new_value], %[ptr]   \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    "1:                                    \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [old_value]"IJr" (old_value),
+      [new_value]"r" (new_value)
+    : "cc", "memory"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
+                                         Atomic64 new_value) {
+  Atomic64 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[result], %[ptr]                \n\t"
+    "stxr %w[temp], %[new_value], %[ptr]   \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [new_value]"r" (new_value)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
+                                          Atomic64 increment) {
+  Atomic64 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                     \n\t"
+    "ldxr %[result], %[ptr]                 \n\t"
+    "add %[result], %[result], %[increment] \n\t"
+    "stxr %w[temp], %[result], %[ptr]       \n\t"
+    "cbnz %w[temp], 0b                      \n\t"
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp),
+      [ptr]"+Q" (*ptr)
+    : [increment]"IJr" (increment)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
+                                        Atomic64 increment) {
+  MemoryBarrier();
+  Atomic64 result = NoBarrier_AtomicIncrement(ptr, increment);
+  MemoryBarrier();
+
+  return result;
+}
+
+inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  Atomic64 prev = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+  MemoryBarrier();
+
+  return prev;
+}
+
+inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  MemoryBarrier();
+  Atomic64 prev = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+
+  return prev;
+}
+
+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) {
+  __asm__ __volatile__ (  // NOLINT
+    "stlr %x[value], %[ptr]  \n\t"
+    : [ptr]"=Q" (*ptr)
+    : [value]"r" (value)
+    : "memory"
+  );  // NOLINT
+}
+
+inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
+  return *ptr;
+}
+
+inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
+  Atomic64 value;
+
+  __asm__ __volatile__ (  // NOLINT
+    "ldar %x[value], %[ptr]  \n\t"
+    : [value]"=r" (value)
+    : [ptr]"Q" (*ptr)
+    : "memory"
+  );  // NOLINT
+
+  return value;
+}
+
+inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
+  MemoryBarrier();
+  return *ptr;
+}
+
+}  // namespace subtle
+}  // namespace base
+
+#endif  // BASE_ATOMICOPS_INTERNALS_ARM64_GCC_H_